sndif: add ABI for para-virtual sound

I'm just wondering if anybody had a chance to look at the patch...

Hi, Konrad!

I see no comments for almost 3 weeks now, so probably there are no objections against this protocol. Can we please move on on this?

Thank you in advance,
Oleksandr

Quoted 1 line · Oleksandr Andrushchenko

I'm just wondering if anybody had a chance to look at the patch...

From: Oleksandr Andrushchenko <[email protected]>

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Signed-off-by Oleksandr Grytsov <[email protected]>

Signed-off-by Oleksandr Dmytryshyn <[email protected]>

Signed-off-by Iurii Konovalenko <[email protected]>

---
Changes since v1:
* removed __attribute__((__packed__)) from all structures definitions

Changes since v2:
* removed all C structures
* added protocol description between frontend and backend drivers

Changes since v3:
* fixed some typos
* renamed XENSND_PCM_FORMAT_FLOAT_** to XENSND_PCM_FORMAT_F32_**
* renamed XENSND_PCM_FORMAT_FLOAT64_** to XENSND_PCM_FORMAT_F64_**
* added 'id' field to the request and response packets
* renamed 'stream_id' to 'stream' in the packets description
* renamed 'pcm_data_rate' to 'pcm_rate' in the packets description
* renamed 'pcm_stream_type' to 'pcm_type' in the packets description
* removed 'stream_id' field from the response packets

Changes since v4:
* renamed 'stream_id' back to the to 'stream' in the packets description
* moved 'id' field to the upper position in the response packets

Changes since v5:
* Slightly reworked request/response packets
* Size of the request/response packet is changed to the 64 bytes
* Now parameters for the XENSND_OP_SET_VOLUME/XENSND_OP_GET_VOLUME are passed via shared page
* Added parameters for the XenBus nodes (now each stream can be mapped to the defined sound device in the backend using those parameters)
* Added XenBus state diagrams description

Changes since v6:
* Reworked streams description in the Backend XenBus Nodes

Changes since v7:
* re-worked backend device parameters to be more generic and flexible
* extended frontend device parameters
* slightly updated state machine description added mute/unmute commands
* added constants for XenStore configuration strings (fields, PCM formats etc.)
* changed request/response structure size from 64 octets to 16
* introduced dynamic buffer allocation instead of
static XENSND_MAX_PAGES_PER_REQUEST
* re-worked open request to allow dynamic buffer allocation
* re-worked read/write/volume requests, so they don't pass grefs:
buffer from the open request is used for these operations to pass data
* specified type of the volume value to be a signed value in steps of 0.001 dBm, while 0 being 0dBm.
* added Linux include file with structure definitions

Changes since v8:
* changed frontend-id to frontend_id
* single sound card support, configured with bunch of devices/streams
* clarifucation made on sample rates and formats expressed as decimals w/o any particular ordering
* put description of migration/disconnection state
* replaced __attribute__((packed)) to __packed
* changed padding of ring structures to 64 to fit cache line
* removeed #ifdef __KERNEL
* explicitly stated which indices in XenStore configuration are contiguous
* added description to what frontend's defaults are
* made names of virtual card/devices optional
* removed PCM_FORMAT_SPECIAL
* changed volume units from dBm to dB

Changes since v9:
* removed sndif_linux.h
* moved all structures from sndif_linux.h to sndif.h
* structures padded where needed
* fixed Hz comment

Changes since v10:
* fixed tabs to 4 spaces to comply with Xen coding style
* added placeholders to empty structures (C89 concern)
* added missing header includes

Changes since v11:
* added XENSND_RSP_NOTSUPP error code
* changed gref[0] to gref[1] with comment
* modified comments on empty structures
* removed "__" from member names
* fixed indentation
* added padding in union xensnd_resp
* changed __XEN_PUBLIC_IO_XENSND_H__ to __XEN_PUBLIC_IO_SNDIF_H__

Changes since v12:
* changed indentation for defines
* missed ";" after gref[1]
* documentation changes
* changed req/resp structures
* changed xensnd_page_directory structure
* pass buffer size in open request

Changes since v13:
* note on usage of grant ref 0
* all page sizes are XEN_PAGE_SIZE
* padding/reserved cleanup/fixes
* removed empty structures

Changes since v14:
* turn padding into reserved
---

---
 xen/include/public/io/sndif.h | 671 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 671 insertions(+)
 create mode 100644 xen/include/public/io/sndif.h

xen/include/public/io/sndif.h new file +63 -0

new file mode 100644
index 0000000..60a6d88
@@ -0,0 +1,671 @@
+/******************************************************************************
+ * sndif.h
+ *
+ * Unified sound-device I/O interface for Xen guest OSes.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Copyright (C) 2013-2015 GlobalLogic Inc.
+ * Copyright (C) 2016 EPAM Systems Inc.
+ *
+ * Authors: Oleksandr Andrushchenko <[email protected]>
+ *          Oleksandr Grytsov <[email protected]>
+ *          Oleksandr Dmytryshyn <[email protected]>
+ *          Iurii Konovalenko <[email protected]>
+ */
+
+#ifndef __XEN_PUBLIC_IO_SNDIF_H__
+#define __XEN_PUBLIC_IO_SNDIF_H__
+
+#include "ring.h"
+#include "../grant_table.h"
+
+/*
+ * Front->back notifications: When enqueuing a new request, sending a
+ * notification can be made conditional on req_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Backends must set
+ * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
+ *
+ * Back->front notifications: When enqueuing a new response, sending a
+ * notification can be made conditional on rsp_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Frontends must set
+ * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
+ */
+
+/*
+ * Feature and Parameter Negotiation
+ * =================================
+ * The two halves of a Para-virtual sound card driver utilize nodes within the
+ * XenStore to communicate capabilities and to negotiate operating parameters.
+ * This section enumerates these nodes which reside in the respective front and
+ * backend portions of the XenStore, following the XenBus convention.
+ *
+ * All data in the XenStore is stored as strings.  Nodes specifying numeric
+ * values are encoded in decimal.  Integer value ranges listed below are
+ * expressed as fixed sized integer types capable of storing the conversion
+ * of a properly formated node string, without loss of information.
+ *

xen/include/public/io/sndif.h new file +6 -0

+ *
+ *----------------------- Virtual sound card settings --------------------------
+ * short-name
+ *      Values:         <char[32]>
+ *
+ *      Short name of the virtual sound card. Optional.

xen/include/public/io/sndif.h new file +133 -0

+ *      driver.
 
 
+ */
+
+/*
+ * STATE DIAGRAMS
+ *
+ *****************************************************************************
+ *                                   Startup                                 *
+ *****************************************************************************
+ *
+ * Tool stack creates front and back state nodes with initial state
+ * XenbusStateInitialising.
+ * Tool stack creates and sets up frontend sound configuration nodes per domain.
+ *
+ * Front                                Back
+ * =================================    =====================================
+ * XenbusStateInitialising              XenbusStateInitialising
+ *                                       o Query backend device identification
+ *                                         data.
+ *                                       o Open and validate backend device.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateInitWait
+ *
+ * o Query frontend configuration
+ * o Allocate and initialize
+ *   event channels per configured
+ *   playback/capture stream.
+ * o Publish transport parameters
+ *   that will be in effect during
+ *   this connection.
+ *              |
+ *              |
+ *              V
+ * XenbusStateInitialised
+ *
+ *                                       o Query frontend transport parameters.
+ *                                       o Connect to the event channels.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateConnected
+ *
+ *  o Create and initialize OS
+ *  virtual sound device instances
+ *  as per configuration.
+ *              |
+ *              |
+ *              V
+ * XenbusStateConnected
+ *
+ *                                      XenbusStateUnknown
+ *                                      XenbusStateClosed
+ *                                      XenbusStateClosing
+ * o Remove virtual sound device
+ * o Remove event channels
+ *              |
+ *              |
+ *              V
+ * XenbusStateClosed
+ *
+ */
+
+/*
+ * PCM FORMATS
+ *
+ * XENSND_PCM_FORMAT_<format>[_<endian>]
+ *
+ * format: <S/U/F><bits> or <name>
+ *     S - signed, U - unsigned, F - float
+ *     bits - 8, 16, 24, 32
+ *     name - MU_LAW, GSM, etc.
+ *
+ * endian: <LE/BE>, may be absent
+ *     LE - Little endian, BE - Big endian
+ */
+#define XENSND_PCM_FORMAT_S8            0
+#define XENSND_PCM_FORMAT_U8            1
+#define XENSND_PCM_FORMAT_S16_LE        2
+#define XENSND_PCM_FORMAT_S16_BE        3
+#define XENSND_PCM_FORMAT_U16_LE        4
+#define XENSND_PCM_FORMAT_U16_BE        5
+#define XENSND_PCM_FORMAT_S24_LE        6
+#define XENSND_PCM_FORMAT_S24_BE        7
+#define XENSND_PCM_FORMAT_U24_LE        8
+#define XENSND_PCM_FORMAT_U24_BE        9
+#define XENSND_PCM_FORMAT_S32_LE        10
+#define XENSND_PCM_FORMAT_S32_BE        11
+#define XENSND_PCM_FORMAT_U32_LE        12
+#define XENSND_PCM_FORMAT_U32_BE        13
+#define XENSND_PCM_FORMAT_F32_LE        14 /* 4-byte float, IEEE-754 32-bit, */
+#define XENSND_PCM_FORMAT_F32_BE        15 /* range -1.0 to 1.0              */
+#define XENSND_PCM_FORMAT_F64_LE        16 /* 8-byte float, IEEE-754 64-bit, */
+#define XENSND_PCM_FORMAT_F64_BE        17 /* range -1.0 to 1.0              */
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE 18
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE 19
+#define XENSND_PCM_FORMAT_MU_LAW        20
+#define XENSND_PCM_FORMAT_A_LAW         21
+#define XENSND_PCM_FORMAT_IMA_ADPCM     22
+#define XENSND_PCM_FORMAT_MPEG          23
+#define XENSND_PCM_FORMAT_GSM           24
+
+/*
+ * REQUEST CODES.
+ */
+#define XENSND_OP_OPEN                  0
+#define XENSND_OP_CLOSE                 1
+#define XENSND_OP_READ                  2
+#define XENSND_OP_WRITE                 3
+#define XENSND_OP_SET_VOLUME            4
+#define XENSND_OP_GET_VOLUME            5
+#define XENSND_OP_MUTE                  6
+#define XENSND_OP_UNMUTE                7
+
+/*
+ * XENSTORE FIELD AND PATH NAME STRINGS, HELPERS.
+ */
+#define XENSND_DRIVER_NAME              "vsnd"
+
+#define XENSND_LIST_SEPARATOR           ";"
+/* Path entries */
+#define XENSND_PATH_DEVICE              "device"
+#define XENSND_PATH_STREAM              "stream"
+/* Field names */
+#define XENSND_FIELD_VCARD_SHORT_NAME   "short-name"
+#define XENSND_FIELD_VCARD_LONG_NAME    "long-name"
+#define XENSND_FIELD_RING_REF           "ring-ref"
+#define XENSND_FIELD_EVT_CHNL           "event-channel"
+#define XENSND_FIELD_DEVICE_NAME        "name"
+#define XENSND_FIELD_TYPE               "type"
+#define XENSND_FIELD_STREAM_INDEX       "index"
+#define XENSND_FIELD_CHANNELS_MIN       "channels-min"

xen/include/public/io/sndif.h new file +23 -0

+
+#define XENSND_PCM_FORMAT_S8_STR        "s8"
+#define XENSND_PCM_FORMAT_U8_STR        "u8"
+#define XENSND_PCM_FORMAT_S16_LE_STR    "s16_le"
+#define XENSND_PCM_FORMAT_S16_BE_STR    "s16_be"
+#define XENSND_PCM_FORMAT_U16_LE_STR    "u16_le"
+#define XENSND_PCM_FORMAT_U16_BE_STR    "u16_be"
+#define XENSND_PCM_FORMAT_S24_LE_STR    "s24_le"
+#define XENSND_PCM_FORMAT_S24_BE_STR    "s24_be"
+#define XENSND_PCM_FORMAT_U24_LE_STR    "u24_le"
+#define XENSND_PCM_FORMAT_U24_BE_STR    "u24_be"
+#define XENSND_PCM_FORMAT_S32_LE_STR    "s32_le"
+#define XENSND_PCM_FORMAT_S32_BE_STR    "s32_be"
+#define XENSND_PCM_FORMAT_U32_LE_STR    "u32_le"
+#define XENSND_PCM_FORMAT_U32_BE_STR    "u32_be"
+#define XENSND_PCM_FORMAT_F32_LE_STR    "float_le"
+#define XENSND_PCM_FORMAT_F32_BE_STR    "float_be"
+#define XENSND_PCM_FORMAT_F64_LE_STR    "float64_le"
+#define XENSND_PCM_FORMAT_F64_BE_STR    "float64_be"
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR "iec958_subframe_le"
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR "iec958_subframe_be"
+#define XENSND_PCM_FORMAT_MU_LAW_STR    "mu_law"
+#define XENSND_PCM_FORMAT_A_LAW_STR     "a_law"

+ *
+ * Description of the protocol between frontend and backend driver.

+ *
+ * The two halves of a Para-virtual sound driver communicate with
+ * each other using a shared page and an event channel.

+ * Shared page contains a ring with request/response packets.
+ *
+ * All reserved fields in the structures below must be 0.
+ *
+ * All request packets have the same length (32 octets)

+ * All request packets have common header:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |

+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+

+ *   id - uint16_t, private guest value, echoed in response
+ *   operation - uint8_t, operation code
+ *   stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry

+ * of the stream)

+ *
+ *
+ * Request open - open a PCM stream for playback or capture:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | XENSND_OP_OPEN | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |

+ * +-----------------+-----------------+-----------------+-----------------+
+ * | pcm_rate |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | pcm_format | pcm_channels | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | buffer_sz |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref_directory_start |

+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+

+ *
+ * pcm_rate - uint32_t, stream data rate, Hz
+ * pcm_format - uint8_t, XENSND_PCM_FORMAT_XXX value
+ * pcm_channels - uint8_t, number of channels of this stream

+ * buffer_sz - uint32_t, buffer size to be allocated in octets

+ * gref_directory_start - grant_ref_t, a reference to the first shared page

+ * describing shared buffer references. At least one page exists. If shared
+ * buffer size exceeds what can be addressed by this single page, then

+ * reference to the next page must be supplied (see gref_dir_next_page below)

xen/include/public/io/sndif.h new file +19 -0

+    uint32_t pcm_rate; /* in Hz */
+    uint8_t pcm_format;
+    uint8_t pcm_channels;
+    uint16_t reserved;
+    uint32_t buffer_sz;
+    grant_ref_t gref_directory_start;
+};
+
+/*
+ * Shared page for XENSND_OP_OPEN buffer descriptor (gref_directory in the
+ *   request) employs a list of pages, describing all pages of the shared data
+ *   buffer:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                          gref_dir_next_page                           |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                                gref[0]                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|

+ * gref[i] - grant_ref_t, reference to a shared page of the buffer
+ * allocated at XENSND_OP_OPEN
+ *
+ * Number of grant_ref_t entries in the whole page directory is not
+ * passed, but instead can be calculated as:
+ * num_grefs_total = (XENSND_OP_OPEN.buffer_sz + XEN_PAGE_SIZE - 1) /
+ * XEN_PAGE_SIZE

+ */

xen/include/public/io/sndif.h new file +12 -0

+
+struct xensnd_page_directory {
+    grant_ref_t gref_dir_next_page;
+    grant_ref_t gref[1]; /* Variable length */
+};
+
+/*
+ *  Request close - close an opened pcm stream:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                | XENSND_OP_CLOSE |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+

+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | offset |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | length |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+

+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * operation - XENSND_OP_READ for read or XENSND_OP_WRITE for write
+ * offset - uint32_t, read or write data offset within the shared buffer
+ * passed with XENSND_OP_OPEN request

+ * length - uint32_t, read or write data length

+ */

xen/include/public/io/sndif.h new file +13 -0

+
+struct xensnd_rw_req {
+    uint32_t offset;
+    uint32_t len;
+};
+
+/*
+ * Request set/get volume - set/get channels' volume of the stream given:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                |    operation    |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |

+ *
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[0] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+

+ * | channel[i] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[XENSND_OP_OPEN.pcm_channels - 1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * channel[i] - sint32_t, volume of i-th channel

+ * Volume is expressed as a signed value in steps of 0.001 dB,
+ * while 0 being 0 dB.
+ */

xen/include/public/io/sndif.h new file +7 -0

+
+/*
+ * Request mute/unmute - mute/unmute stream:
 
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                |    operation    |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+

+ *
+ * 0 octet
+ * +-----------------------------------------------------------------------+
+ * | channel[0] |
+ * +-----------------------------------------------------------------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------------------------------------------------------------+
+ * | channel[i] |
+ * +-----------------------------------------------------------------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------------------------------------------------------------+
+ * | channel[XENSND_OP_OPEN.pcm_channels - 1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * channel[i] - uint8_t, non-zero if i-th channel needs to be muted/unmuted
+ */

xen/include/public/io/sndif.h new file +12 -0

+
+/*
+ * All response packets have the same length (32 octets)
+ *
+ * Response for all requests:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                |    operation    |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |      status     |                      reserved                       |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |

+ */

xen/include/public/io/sndif.h new file +24 -0

+
+struct xensnd_req {
+    uint16_t id;
+    uint8_t operation;
+    uint8_t stream_idx;
+    uint32_t reserved;
+    union {
+        struct xensnd_open_req open;
+        struct xensnd_rw_req rw;
+        uint8_t reserved[24];
+    } op;
+};
+
+struct xensnd_resp {
+    uint16_t id;
+    uint8_t operation;
+    uint8_t stream_idx;
+    int8_t status;
+    uint8_t reserved[27];
+};
+
+DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);
+
+#endif /* __XEN_PUBLIC_IO_SNDIF_H__ */

Signature · 1 line

2.7.4

Quoted 1 line · Oleksandr Andrushchenko

From: Oleksandr Andrushchenko <[email protected]>

Usually one also puts somethign in the commit description.

When I applied this to me tree I got:

[konrad@char xen]$ git log --oneline HEAD^..
ecc7711 This is the ABI for the two halves of a para-virtualized sound driver to communicate with each to other. [konrad@char xen]$

Also, thank you for the including the pahole output!

Quoted 183 lines

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Signed-off-by Oleksandr Grytsov <[email protected]>

Signed-off-by Oleksandr Dmytryshyn <[email protected]>

Signed-off-by Iurii Konovalenko <[email protected]>

---
Changes since v1:
* removed __attribute__((__packed__)) from all structures definitions

Changes since v2:
* removed all C structures
* added protocol description between frontend and backend drivers

Changes since v3:
* fixed some typos
* renamed XENSND_PCM_FORMAT_FLOAT_** to XENSND_PCM_FORMAT_F32_**
* renamed XENSND_PCM_FORMAT_FLOAT64_** to XENSND_PCM_FORMAT_F64_**
* added 'id' field to the request and response packets
* renamed 'stream_id' to 'stream' in the packets description
* renamed 'pcm_data_rate' to 'pcm_rate' in the packets description
* renamed 'pcm_stream_type' to 'pcm_type' in the packets description
* removed 'stream_id' field from the response packets

Changes since v4:
* renamed 'stream_id' back to the to 'stream' in the packets description
* moved 'id' field to the upper position in the response packets

Changes since v5:
* Slightly reworked request/response packets
* Size of the request/response packet is changed to the 64 bytes
* Now parameters for the XENSND_OP_SET_VOLUME/XENSND_OP_GET_VOLUME are passed via shared page
* Added parameters for the XenBus nodes (now each stream can be mapped to the defined sound device in the backend using those parameters)
* Added XenBus state diagrams description

Changes since v6:
* Reworked streams description in the Backend XenBus Nodes

Changes since v7:
* re-worked backend device parameters to be more generic and flexible
* extended frontend device parameters
* slightly updated state machine description added mute/unmute commands
* added constants for XenStore configuration strings (fields, PCM formats etc.)
* changed request/response structure size from 64 octets to 16
* introduced dynamic buffer allocation instead of
static XENSND_MAX_PAGES_PER_REQUEST
* re-worked open request to allow dynamic buffer allocation
* re-worked read/write/volume requests, so they don't pass grefs:
buffer from the open request is used for these operations to pass data
* specified type of the volume value to be a signed value in steps

    of 0.001 dBm, while 0 being 0dBm.

* added Linux include file with structure definitions

Changes since v8:
* changed frontend-id to frontend_id
* single sound card support, configured with bunch of devices/streams
* clarifucation made on sample rates and formats expressed as decimals w/o any particular ordering
* put description of migration/disconnection state
* replaced __attribute__((packed)) to __packed
* changed padding of ring structures to 64 to fit cache line
* removeed #ifdef __KERNEL
* explicitly stated which indices in XenStore configuration are contiguous
* added description to what frontend's defaults are
* made names of virtual card/devices optional
* removed PCM_FORMAT_SPECIAL
* changed volume units from dBm to dB

Changes since v9:
* removed sndif_linux.h
* moved all structures from sndif_linux.h to sndif.h
* structures padded where needed
* fixed Hz comment

Changes since v10:
* fixed tabs to 4 spaces to comply with Xen coding style
* added placeholders to empty structures (C89 concern)
* added missing header includes

Changes since v11:
* added XENSND_RSP_NOTSUPP error code
* changed gref[0] to gref[1] with comment
* modified comments on empty structures
* removed "__" from member names
* fixed indentation
* added padding in union xensnd_resp
* changed __XEN_PUBLIC_IO_XENSND_H__ to __XEN_PUBLIC_IO_SNDIF_H__

Changes since v12:
* changed indentation for defines
* missed ";" after gref[1]
* documentation changes
* changed req/resp structures
* changed xensnd_page_directory structure
* pass buffer size in open request

Changes since v13:
* note on usage of grant ref 0
* all page sizes are XEN_PAGE_SIZE
* padding/reserved cleanup/fixes
* removed empty structures

Changes since v14:
* turn padding into reserved
---

---
  xen/include/public/io/sndif.h | 671 ++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 671 insertions(+)

create mode 100644 xen/include/public/io/sndif.h

xen/include/public/io/sndif.h new file +63 -0

new file mode 100644
index 0000000..60a6d88
@@ -0,0 +1,671 @@
+/******************************************************************************
+ * sndif.h
+ *
+ * Unified sound-device I/O interface for Xen guest OSes.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Copyright (C) 2013-2015 GlobalLogic Inc.
+ * Copyright (C) 2016 EPAM Systems Inc.
+ *
+ * Authors: Oleksandr Andrushchenko <[email protected]>
+ *          Oleksandr Grytsov <[email protected]>
+ *          Oleksandr Dmytryshyn <[email protected]>
+ *          Iurii Konovalenko <[email protected]>
+ */
+
+#ifndef __XEN_PUBLIC_IO_SNDIF_H__
+#define __XEN_PUBLIC_IO_SNDIF_H__
+
+#include "ring.h"
+#include "../grant_table.h"
+
+/*
+ * Front->back notifications: When enqueuing a new request, sending a
+ * notification can be made conditional on req_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Backends must set
+ * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
+ *
+ * Back->front notifications: When enqueuing a new response, sending a
+ * notification can be made conditional on rsp_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Frontends must set
+ * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
+ */
+
+/*
+ * Feature and Parameter Negotiation
+ * =================================
+ * The two halves of a Para-virtual sound card driver utilize nodes within the
+ * XenStore to communicate capabilities and to negotiate operating parameters.
+ * This section enumerates these nodes which reside in the respective front and
+ * backend portions of the XenStore, following the XenBus convention.
+ *
+ * All data in the XenStore is stored as strings.  Nodes specifying numeric
+ * values are encoded in decimal.  Integer value ranges listed below are
+ * expressed as fixed sized integer types capable of storing the conversion
+ * of a properly formated node string, without loss of information.
+ *

xen/include/public/io/sndif.h line 73

Quoted 10 lines

xen/include/public/io/sndif.h new file +10 -0

+ *****************************************************************************
+ *                            Backend XenBus Nodes
+ *****************************************************************************
+ *
+ *-------------------------------- Addressing ---------------------------------
+ *
+ * Indices used to address frontends, driver instances, cards,
+ * devices and streams.
+ *
+ * frontend_id

The rest of the drivers use - instead of _.

Is there a particular reason you need to have _ ?

See vscsiif.h and console and vkbd. Actually the last ones don't mention it in the header but the libxl constructs these.

xen/include/public/io/sndif.h line 74

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 78

Quoted 4 lines

xen/include/public/io/sndif.h new file +4 -0

+ *
+ *      Domain ID of the sound frontend.
+ *
+ * drv_idx

Again, can this be - ?

xen/include/public/io/sndif.h line 79

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 83

Quoted 4 lines

xen/include/public/io/sndif.h new file +4 -0

+ *
+ *      Zero based contiguous index of the virtualized sound driver instance in
+ *      this domain. Multiple PV drivers are allowed in the domain
+ *      at the same time.

This is not needed.

We already have this information in the XenStore directory:

/local/domain/0/backend/vsnd/2/0/frontend-id = 2
/local/domain/0/backend/vsnd/2/1/frontend-id = 2
..
/local/domain/0/backend/vsnd/2/N/frontend-id = 2

(which would be similar to what 'vbd', 'console' and 'vif' do).

xen/include/public/io/sndif.h line 85

Quoted 3 lines

xen/include/public/io/sndif.h new file +2 -0

+ *
+ * dev_id

s/_/-/

xen/include/public/io/sndif.h line 86

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ *      Values:         <uint>

uint_32t

xen/include/public/io/sndif.h line 89

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ *      Unique device ID.
+ *      Doesn't have to be zero based and/or to be contiguous.

Is uint enough? Or would it be better to have an <string> if this is some form of SHA-1 value?

xen/include/public/io/sndif.h line 91

Quoted 2 lines

xen/include/public/io/sndif.h new file +2 -0

+ *
+ * stream_idx

s/_/-/

xen/include/public/io/sndif.h line 92

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ *      Values:         <uint>

uint_32t

[edit, based on the struct xensnd_req this has to be uint_8t] ?

xen/include/public/io/sndif.h line 101

Quoted 9 lines

xen/include/public/io/sndif.h new file +9 -0

+ *
+ *      Zero based contiguous index of the stream of the device.
+ *
+ * Example for the frontend running in domain 5, instance of the driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ *         device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Why do you need 'device' ?

Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

xen/include/public/io/sndif.h line 105

Quoted 6 lines

xen/include/public/io/sndif.h new file +4 -0

+ *
+ *------------------------------- PCM settings --------------------------------
+ *
+ * Every virtualized sound frontend has set of devices and streams, each

frontend or backend?

I would think backend since this is still the backend section?

xen/include/public/io/sndif.h line 117

Quoted 13 lines

xen/include/public/io/sndif.h new file +12 -0

+ * is individually configured. Part of the PCM configuration can be defined at
+ * higher level and be fully or partially re-used by the underlying layers.
+ * These configuration values are:
+ *  o number of channels (min/max)
+ *  o supported sample rates
+ *  o supported sample formats.
+ * E.g. one can define these values for the whole driver, device or stream.
+ * Every underlying layer in turn can re-define some or all of them to better
+ * fit its needs. For example, driver may define number of channels to be
+ * in [1; 8] range, and some particular stream may be limited to [1; 2] only.
+ * The rule is that the underlying layer must be a subset of the upper layer
+ * range.

OK, so these are more of 'global ones'?

xen/include/public/io/sndif.h line 120

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ * Note: if any of the values are not defined then PV driver should use
+ * its default values instead.

How is that suppose to work? What if the PV driver by default wants to use say 314156 channels and the backend does not expose any? Can it use that? I presume it could try.. and it would fail but that hardly seems nice.

xen/include/public/io/sndif.h line 123

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ * channels-min
+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 126

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ *      The minimum amount of channels that is supported.
+ *      Must be at least 1. If not defined then use frontend's default.

This is odd. This whole section is for the backend, so how can the backend not have this defined?

Do you mean to say that this parameter is optional? Perhaps then say right before 'The minimum' include '(optional)'

Anyhow where do you envision this optional global value to be?

/local/domain/0/backend/vsnd/5/channels-[min|max] ?

Perhaps mention that in the start of this section:

These global values are under the backend 'vsnd' directory, as so:

/local/domain/0/backends/vsnd/<front-id>/channels-[min|max]

Thought I think there is probably a better way to
say this..

xen/include/public/io/sndif.h line 129

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ * channels-max
+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 133

Quoted 4 lines

xen/include/public/io/sndif.h new file +4 -0

+ *
+ *      The maximum amount of channels that is supported.
+ *      Must be at least <channels-min>. If not defined then use frontend's
+ *      default.

I am still having trouble understanding how the backend is suppose to use the frontend's default.

Perhaps you want to say:

If this value is not exposed by the backend the frontend is permitted to use its default values.

?

xen/include/public/io/sndif.h line 136

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ * sample-rates
+ *      Values:         <list of uints>

.. of uint32_t

xen/include/public/io/sndif.h line 139

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ *      List of supported sample rates separated by XENSND_LIST_SEPARATOR.
+ *      If not defined then use frontend's default. Sample rates are expressed

Ahain this 'If not defined then use fronten'ds default' could be written a bit differently.

xen/include/public/io/sndif.h line 146

Quoted 7 lines

xen/include/public/io/sndif.h new file +7 -0

+ *      as a list of decimal values w/o any ordering requirement.
+ *
+ * sample-formats
+ *      Values:         <list of XENSND_PCM_FORMAT_XXX_STR>
+ *
+ *      List of supported sample formats separated by XENSND_LIST_SEPARATOR.
+ *      If not defined then use frontend's default.

Again, this does not sound right. The backend has no clue what the frontend defaults are.

xen/include/public/io/sndif.h line 149

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ * buffer-size
+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 156

Quoted 7 lines

xen/include/public/io/sndif.h new file +7 -0

+ *
+ *      The maximum size in octets of the buffer to allocate per stream.
+ *
+ * Example configuration:
+ *
+ * Driver configuration used by all streams:
+ * /local/domain/5/device/vsnd/0/sample-formats = "s8;u8;s16_le;s16_be"

Huh? But this is a backend value? Don't you mean:

/local/domain/0/backend/vsnd/5/sample-formats = "s8;u8;s16_le;s16_be" ?

xen/include/public/io/sndif.h line 157

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ * Stream overrides sample rates supported:

-EPARSE

xen/include/public/io/sndif.h line 159

Quoted 3 lines

xen/include/public/io/sndif.h new file +2 -0

+ * /local/domain/5/device/vsnd/0/device/2/stream/0/sample-rates =
+ *        "8000;22050;44100;48000"

/local/domain/0/backend/vsnd/5/2/stream/0/sample-rates ="8000;22050;44100;48000"

But that is wrong as this section is about global values so they would be more like:

/local/domain/0/backend/vsnd/5/sample-rates ="8000;22050;44100;48000"

?

Quoted 6 lines

xen/include/public/io/sndif.h new file +6 -0

+ *
+ *----------------------- Virtual sound card settings --------------------------
+ * short-name
+ *      Values:         <char[32]>
+ *
+ *      Short name of the virtual sound card. Optional.

xen/include/public/io/sndif.h line 175

Quoted 10 lines

xen/include/public/io/sndif.h new file +10 -0

+ *
+ * long-name
+ *      Values:         <char[80]>
+ *
+ *      Long name of the virtual sound card. Optional.
+ *
+ * For example,
+ * /local/domain/5/device/vsnd/0/short-name = "Virtual audio"
+ * /local/domain/5/device/vsnd/0/long-name =
+ *         "Virtual audio at center stack"

This should be inverted. That is this is on the backend side:

/local/domain/0/backend/vsnd/5/0/2/short-name = "Virtual audio"

And so on.

Also how come your example is missing the device part?

Wait, why do you have an an device below but ... not here? Why not group them together?

That is why not have 'short-name' ,'long-name' and 'name' in the same directory?

xen/include/public/io/sndif.h line 184

Quoted 10 lines

xen/include/public/io/sndif.h new file +9 -0

+ *
+ *----------------------------- Device settings --------------------------------
+ * name
+ *      Values:         <char[80]>
+ *
+ *      Name of the sound device within the virtual sound card. Optional.
+ *
+ * For example,
+ * /local/domain/5/device/vsnd/0/device/0/name = "General analog"

The example you used at start had a device value of 2. It may be better to use that here, so :

/local/domain/0/backend/vsnd/5/2/name = "General analog"

xen/include/public/io/sndif.h line 196

Quoted 12 lines

xen/include/public/io/sndif.h new file +12 -0

+ *
+ *----------------------------- Stream settings -------------------------------
+ *
+ * type
+ *      Values:         "p", "c"
+ *
+ *      Stream type: "p" - playback stream, "c" - capture stream
+ *
+ *      If both capture and playback are needed then two streams need to be
+ *      defined under the same device. For example,
+ *      /local/domain/5/device/vsnd/0/device/0/stream/0/type = "p"
+ *      /local/domain/5/device/vsnd/0/device/0/stream/1/type = "c"

OK, but again:
/local/domain/0/backend/vsnd/5/2/0/stream/0/type = "p" /local/domain/0/backend/vsnd/5/2/0/stream/1/type = "c"

Do you want also an 'feature-version' to identify what version the backend exposes?

xen/include/public/io/sndif.h line 204

Quoted 8 lines

xen/include/public/io/sndif.h new file +8 -0

+ *
+ *****************************************************************************
+ *                            Frontend XenBus Nodes
+ *****************************************************************************
+ *
+ *----------------------- Request Transport Parameters -----------------------
+ *
+ * These are per stream.

.. which means they are also per device right?

So one can have something like this:

/local/domain/5/device/vsnd/2/stream/0/event-channel /local/domain/5/device/vsnd/0/stream/0/event-channel /local/domain/5/device/vsnd/2/stream/1/event-channel /local/domain/5/device/vsnd/0/stream/0/event-channel

xen/include/public/io/sndif.h line 207

Quoted 3 lines

xen/include/public/io/sndif.h new file +3 -0

+ *
+ * event-channel
+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 213

Quoted 6 lines

xen/include/public/io/sndif.h new file +6 -0

+ *
+ *      The identifier of the Xen event channel used to signal activity
+ *      in the ring buffer.
+ *
+ * ring-ref
+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 218

Quoted 5 lines

xen/include/public/io/sndif.h new file +5 -0

+ *
+ *      The Xen grant reference granting permission for the backend to map
+ *      a sole page in a single page sized ring buffer.
+ *
+ * index

Why not 'unique-id' ?

xen/include/public/io/sndif.h line 219

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ *      Values:         <uint>

uint32_t

xen/include/public/io/sndif.h line 223

Quoted 4 lines

xen/include/public/io/sndif.h new file +4 -0

+ *
+ *      After stream initialization it is assigned a unique ID (within the front
+ *      driver), so every stream of the frontend can be identified by the
+ *      backend by this ID. This is not equal to stream_idx as the later is

s/stream_idx/steam-idx/

xen/include/public/io/sndif.h line 224

Quoted 1 line

xen/include/public/io/sndif.h new file +1 -0

+ *      zero based within a device, but this index is contiguous within the

contingous

Quoted 134 lines

xen/include/public/io/sndif.h new file +133 -0

+ *      driver.
 
+ */
+
+/*
+ * STATE DIAGRAMS
+ *
+ *****************************************************************************
+ *                                   Startup                                 *
+ *****************************************************************************
+ *
+ * Tool stack creates front and back state nodes with initial state
+ * XenbusStateInitialising.
+ * Tool stack creates and sets up frontend sound configuration nodes per domain.
+ *
+ * Front                                Back
+ * =================================    =====================================
+ * XenbusStateInitialising              XenbusStateInitialising
+ *                                       o Query backend device identification
+ *                                         data.
+ *                                       o Open and validate backend device.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateInitWait
+ *
+ * o Query frontend configuration
+ * o Allocate and initialize
+ *   event channels per configured
+ *   playback/capture stream.
+ * o Publish transport parameters
+ *   that will be in effect during
+ *   this connection.
+ *              |
+ *              |
+ *              V
+ * XenbusStateInitialised
+ *
+ *                                       o Query frontend transport parameters.
+ *                                       o Connect to the event channels.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateConnected
+ *
+ *  o Create and initialize OS
+ *  virtual sound device instances
+ *  as per configuration.
+ *              |
+ *              |
+ *              V
+ * XenbusStateConnected
+ *
+ *                                      XenbusStateUnknown
+ *                                      XenbusStateClosed
+ *                                      XenbusStateClosing
+ * o Remove virtual sound device
+ * o Remove event channels
+ *              |
+ *              |
+ *              V
+ * XenbusStateClosed
+ *
+ */
+
+/*
+ * PCM FORMATS
+ *
+ * XENSND_PCM_FORMAT_<format>[_<endian>]
+ *
+ * format: <S/U/F><bits> or <name>
+ *     S - signed, U - unsigned, F - float
+ *     bits - 8, 16, 24, 32
+ *     name - MU_LAW, GSM, etc.
+ *
+ * endian: <LE/BE>, may be absent
+ *     LE - Little endian, BE - Big endian
+ */
+#define XENSND_PCM_FORMAT_S8            0
+#define XENSND_PCM_FORMAT_U8            1
+#define XENSND_PCM_FORMAT_S16_LE        2
+#define XENSND_PCM_FORMAT_S16_BE        3
+#define XENSND_PCM_FORMAT_U16_LE        4
+#define XENSND_PCM_FORMAT_U16_BE        5
+#define XENSND_PCM_FORMAT_S24_LE        6
+#define XENSND_PCM_FORMAT_S24_BE        7
+#define XENSND_PCM_FORMAT_U24_LE        8
+#define XENSND_PCM_FORMAT_U24_BE        9
+#define XENSND_PCM_FORMAT_S32_LE        10
+#define XENSND_PCM_FORMAT_S32_BE        11
+#define XENSND_PCM_FORMAT_U32_LE        12
+#define XENSND_PCM_FORMAT_U32_BE        13
+#define XENSND_PCM_FORMAT_F32_LE        14 /* 4-byte float, IEEE-754 32-bit, */
+#define XENSND_PCM_FORMAT_F32_BE        15 /* range -1.0 to 1.0              */
+#define XENSND_PCM_FORMAT_F64_LE        16 /* 8-byte float, IEEE-754 64-bit, */
+#define XENSND_PCM_FORMAT_F64_BE        17 /* range -1.0 to 1.0              */
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE 18
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE 19
+#define XENSND_PCM_FORMAT_MU_LAW        20
+#define XENSND_PCM_FORMAT_A_LAW         21
+#define XENSND_PCM_FORMAT_IMA_ADPCM     22
+#define XENSND_PCM_FORMAT_MPEG          23
+#define XENSND_PCM_FORMAT_GSM           24
+
+/*
+ * REQUEST CODES.
+ */
+#define XENSND_OP_OPEN                  0
+#define XENSND_OP_CLOSE                 1
+#define XENSND_OP_READ                  2
+#define XENSND_OP_WRITE                 3
+#define XENSND_OP_SET_VOLUME            4
+#define XENSND_OP_GET_VOLUME            5
+#define XENSND_OP_MUTE                  6
+#define XENSND_OP_UNMUTE                7
+
+/*
+ * XENSTORE FIELD AND PATH NAME STRINGS, HELPERS.
+ */
+#define XENSND_DRIVER_NAME              "vsnd"
+
+#define XENSND_LIST_SEPARATOR           ";"
+/* Path entries */
+#define XENSND_PATH_DEVICE              "device"
+#define XENSND_PATH_STREAM              "stream"
+/* Field names */
+#define XENSND_FIELD_VCARD_SHORT_NAME   "short-name"
+#define XENSND_FIELD_VCARD_LONG_NAME    "long-name"
+#define XENSND_FIELD_RING_REF           "ring-ref"
+#define XENSND_FIELD_EVT_CHNL           "event-channel"
+#define XENSND_FIELD_DEVICE_NAME        "name"
+#define XENSND_FIELD_TYPE               "type"
+#define XENSND_FIELD_STREAM_INDEX       "index"
+#define XENSND_FIELD_CHANNELS_MIN       "channels-min"

xen/include/public/io/sndif.h line 367

Quoted 10 lines

xen/include/public/io/sndif.h new file +10 -0

+#define XENSND_FIELD_CHANNELS_MAX       "channels-max"
+#define XENSND_FIELD_SAMPLE_RATES       "sample-rates"
+#define XENSND_FIELD_SAMPLE_FORMATS     "sample-formats"
+#define XENSND_FIELD_BUFFER_SIZE        "buffer-size"
+
+/* Stream type field values. */
+#define XENSND_STREAM_TYPE_PLAYBACK     "p"
+#define XENSND_STREAM_TYPE_CAPTURE      "c"
+/* Sample rate max string length */
+#define XENSND_SAMPLE_RATE_MAX_LEN      6

Hm, but it is uint32_t which can be much much higher than 6.

4294967295

11 characters?

xen/include/public/io/sndif.h line 369

Quoted 2 lines

xen/include/public/io/sndif.h new file +2 -0

+/* Sample format field values */
+#define XENSND_SAMPLE_FORMAT_MAX_LEN    24

You sure? You may want to make that clear in 'sample-format' section that the maximum of a string can be 24 characters.

And also explain why 24 characters.

Quoted 26 lines

xen/include/public/io/sndif.h new file +26 -0

+
+#define XENSND_PCM_FORMAT_S8_STR        "s8"
+#define XENSND_PCM_FORMAT_U8_STR        "u8"
+#define XENSND_PCM_FORMAT_S16_LE_STR    "s16_le"
+#define XENSND_PCM_FORMAT_S16_BE_STR    "s16_be"
+#define XENSND_PCM_FORMAT_U16_LE_STR    "u16_le"
+#define XENSND_PCM_FORMAT_U16_BE_STR    "u16_be"
+#define XENSND_PCM_FORMAT_S24_LE_STR    "s24_le"
+#define XENSND_PCM_FORMAT_S24_BE_STR    "s24_be"
+#define XENSND_PCM_FORMAT_U24_LE_STR    "u24_le"
+#define XENSND_PCM_FORMAT_U24_BE_STR    "u24_be"
+#define XENSND_PCM_FORMAT_S32_LE_STR    "s32_le"
+#define XENSND_PCM_FORMAT_S32_BE_STR    "s32_be"
+#define XENSND_PCM_FORMAT_U32_LE_STR    "u32_le"
+#define XENSND_PCM_FORMAT_U32_BE_STR    "u32_be"
+#define XENSND_PCM_FORMAT_F32_LE_STR    "float_le"
+#define XENSND_PCM_FORMAT_F32_BE_STR    "float_be"
+#define XENSND_PCM_FORMAT_F64_LE_STR    "float64_le"
+#define XENSND_PCM_FORMAT_F64_BE_STR    "float64_be"
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR "iec958_subframe_le"
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR "iec958_subframe_be"
+#define XENSND_PCM_FORMAT_MU_LAW_STR    "mu_law"
+#define XENSND_PCM_FORMAT_A_LAW_STR     "a_law"
+#define XENSND_PCM_FORMAT_IMA_ADPCM_STR "ima_adpcm"
+#define XENSND_PCM_FORMAT_MPEG_STR      "mpeg"
+#define XENSND_PCM_FORMAT_GSM_STR       "gsm"

xen/include/public/io/sndif.h line 402

Quoted 7 lines

xen/include/public/io/sndif.h new file +7 -0

+
+/*
+ * STATUS RETURN CODES.
+ */
+/* Operation not supported. */
+#define XENSND_RSP_NOTSUPP              (-2)
+/* Operation failed for some unspecified reason (e. g. -EIO). */

Is that the -EIO going to be exposed somewhere?

Inside of the
'struct xensnd_resp' ?

Would it make sense to have it exposed there? Is that what 'status' is for?

Why not have an 'err' and mandate that it use POSIX return values?

xen/include/public/io/sndif.h line 413

Quoted 12 lines

xen/include/public/io/sndif.h new file +11 -0

+#define XENSND_RSP_ERROR                (-1)
+/* Operation completed successfully. */
+#define XENSND_RSP_OKAY                 0
+
+/*
+ * Assumptions:
+ *   o usage of grant reference 0 as invalid grant reference:
+ *     grant reference 0 is valid, but never exposed to a PV driver,
+ *     because of the fact it is already in use/reserved by the PV console.
+ *   o all references in this document to page sizes must be treated
+ *     as pages of size XEN_PAGE_SIZE unless  otherwise noted.

^- extra space

Quoted 3 lines

+ *
+ * Description of the protocol between frontend and backend driver.

Is this suppose to have an:
-----------------------------------------
underneath it?

Quoted 3 lines

+ *
+ * The two halves of a Para-virtual sound driver communicate with
+ * each other using a shared page and an event channel.

shared pages and event channels?

Since it looks like you can have

/local/domain/<frontend-id>/device/vsnd/<device-id>/stream/<stream-id>/event-channel

And you can have N device-id and M stream-id ?

Quoted 5 lines

+ * Shared page contains a ring with request/response packets.
+ *
+ * All reserved fields in the structures below must be 0.
+ *
+ * All request packets have the same length (32 octets)

Which implies you can have at maximum 64 requests?

[64 bytes for the four RING_IDX along with the 48 of padding, that means 4032 left, but since we need this to be modulo 2 the best we can do is 2^6.

Quoted 6 lines

+ * All request packets have common header:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |

Why the stream_idx ? Your 'ring-ref' is rooted from the '<stream-idx>' so the frontend and backend already know this.

Quoted 7 lines

+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+

+ *   id - uint16_t, private guest value, echoed in response
+ *   operation - uint8_t, operation code
+ *   stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry

+ * of the stream)

Why do you need this duplicate information?

Quoted 17 lines

+ *
+ *
+ * Request open - open a PCM stream for playback or capture:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | XENSND_OP_OPEN | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | pcm_rate |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | pcm_format | pcm_channels | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | buffer_sz |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref_directory_start |

Perhaps 'gref_list' ?

Quoted 8 lines

+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+

Quoted 4 lines

+ *
+ * pcm_rate - uint32_t, stream data rate, Hz
+ * pcm_format - uint8_t, XENSND_PCM_FORMAT_XXX value
+ * pcm_channels - uint8_t, number of channels of this stream

.. And I presume this should be between 'channels-min' and 'channels-max'? Is it OK to have to say 255 ? What are the boundary values?

Quoted 1 line

+ * buffer_sz - uint32_t, buffer size to be allocated in octets

Is there an maximum? Or a minimum?

Why have it in bytes? Why not in the amount of grants you need? Perhaps call it 'gref_nr' ? That way your computation on how many grants you need is well simplified.

Quoted 3 lines

+ * gref_directory_start - grant_ref_t, a reference to the first shared page

s/gref_directory_start/gref_list/ ?

Quoted 2 lines

+ * describing shared buffer references. At least one page exists. If shared
+ * buffer size exceeds what can be addressed by this single page, then

s/shared buffer size/buffer_sz/ ?

Quoted 2 lines

+ * reference to the next page must be supplied (see gref_dir_next_page below)

Now what if grefs_nr (or buffer_sz) is say 1 page (4096). Does that mean that gref_directory_start still needs to point to page which only has two entries: 0, <grant ref> ?

Or can it be simplified and this gref_directory_start would be used for data instead?

I think that is what you saying ("If shared .. " which would imply that if "if !shared" then something else can be done?) but the start
says: "a reference to the first shared page describind shared buffer references" which implies you do
need this extra indirect page even if the buffer_sz is say 4096. ?

xen/include/public/io/sndif.h

Quoted 5 lines

+ */

xen/include/public/io/sndif.h new file +2 -0

+
+struct xensnd_open_req {

s/_open_req/_req_open/

Quoted 22 lines

xen/include/public/io/sndif.h new file +22 -0

+    uint32_t pcm_rate; /* in Hz */
+    uint8_t pcm_format;
+    uint8_t pcm_channels;
+    uint16_t reserved;
+    uint32_t buffer_sz;
+    grant_ref_t gref_directory_start;
+};
+
+/*
+ * Shared page for XENSND_OP_OPEN buffer descriptor (gref_directory in the
+ *   request) employs a list of pages, describing all pages of the shared data
+ *   buffer:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                          gref_dir_next_page                           |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                                gref[0]                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                                gref[i]                                |
+ * +-----------------+-----------------+-----------------+-----------------+

Quoted 7 lines

+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref[N -1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * gref_dir_next_page - grant_ref_t, reference to the next page describing
+ * page directory. Must be 0 if no more pages in the list.

s/no more page/there are no more/

Quoted 8 lines

+ * gref[i] - grant_ref_t, reference to a shared page of the buffer
+ * allocated at XENSND_OP_OPEN
+ *
+ * Number of grant_ref_t entries in the whole page directory is not
+ * passed, but instead can be calculated as:
+ * num_grefs_total = (XENSND_OP_OPEN.buffer_sz + XEN_PAGE_SIZE - 1) /
+ * XEN_PAGE_SIZE

And what are the expected errors? Woudl it make sense to define those? Say:

Returns:

-ENOBUFS: Cannot map that many buffers.
-EINVAL: Incorrect values in the requst?

-

Quoted 17 lines

+ */

xen/include/public/io/sndif.h new file +16 -0

+
+struct xensnd_page_directory {
+    grant_ref_t gref_dir_next_page;
+    grant_ref_t gref[1]; /* Variable length */
+};
+
+/*
+ *  Request close - close an opened pcm stream:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                | XENSND_OP_CLOSE |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+

xen/include/public/io/sndif.h line 528

Quoted 6 lines

+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ */

xen/include/public/io/sndif.h new file +3 -0

+
+/*
+ * Request read/write - used for read (for capture) or write (for playback):

Maybe say also that XENSND_OP_OPEN MUST be called before these operations are permitted.

Quoted 12 lines

+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | offset |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | length |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+

Quoted 8 lines

+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * operation - XENSND_OP_READ for read or XENSND_OP_WRITE for write
+ * offset - uint32_t, read or write data offset within the shared buffer
+ * passed with XENSND_OP_OPEN request

May also want to say that this offset must be less than buffer_sz.

In octets? May want to say that explicitly.

Quoted 2 lines

+ * length - uint32_t, read or write data length

In octets?

Quoted 14 lines

+ */

xen/include/public/io/sndif.h new file +13 -0

+
+struct xensnd_rw_req {
+    uint32_t offset;
+    uint32_t len;
+};
+
+/*
+ * Request set/get volume - set/get channels' volume of the stream given:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                |    operation    |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |

xen/include/public/io/sndif.h line 573

Quoted 10 lines

xen/include/public/io/sndif.h new file +10 -0

+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * operation - XENSND_OP_SET_VOLUME for volume set
+ *   or XENSND_OP_GET_VOLUME for volume get
+ * Buffer passed with XENSND_OP_OPEN is used to exchange volume
+ * values:

Oh. That means you these operation are in effect 'barrier' ones.

As the buffer must be flushed before hand otherwise you would be overwriting data stream information.

You should probably mention this semantic need?

Or alternatively the XENSND_OP_SET_VOLUME/XENSND_OP_GET_VOLUME could have a similar structure to 'struct xensnd_rw_req' so that you have the offset and len?

Quoted 7 lines

+ *
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[0] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+

Quoted 8 lines

+ * | channel[i] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[XENSND_OP_OPEN.pcm_channels - 1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * channel[i] - sint32_t, volume of i-th channel

You may want to say that i is uint8_t.

Quoted 11 lines

+ * Volume is expressed as a signed value in steps of 0.001 dB,
+ * while 0 being 0 dB.
+ */

xen/include/public/io/sndif.h new file +7 -0

+
+/*
+ * Request mute/unmute - mute/unmute stream:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                |    operation    |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+

xen/include/public/io/sndif.h line 608

Quoted 10 lines

xen/include/public/io/sndif.h new file +10 -0

+ * |                               reserved                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * operation - XENSND_OP_MUTE for mute or XENSND_OP_UNMUTE for unmute
+ * Buffer passed with XENSND_OP_OPEN is used to exchange mute/unmute
+ * values:

Again, same comments as above.

Quoted 31 lines

+ *
+ * 0 octet
+ * +-----------------------------------------------------------------------+
+ * | channel[0] |
+ * +-----------------------------------------------------------------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------------------------------------------------------------+
+ * | channel[i] |
+ * +-----------------------------------------------------------------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------------------------------------------------------------+
+ * | channel[XENSND_OP_OPEN.pcm_channels - 1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * channel[i] - uint8_t, non-zero if i-th channel needs to be muted/unmuted
+ */

xen/include/public/io/sndif.h new file +15 -0

+
+/*
+ * All response packets have the same length (32 octets)
+ *
+ * Response for all requests:
+ *          0                 1                  2                3        octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                 id                |    operation    |     stream_idx  |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |      status     |                      reserved                       |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |                               reserved                                |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+

Quoted 7 lines

+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, copied from the request
+ * stream_idx - uint8_t, copied from request
+ * operation - uint8_t, XENSND_OP_* - copied from request
+ * status - int8_t, response status (XENSND_RSP_*)

Could this become an 'err' and the POSIX values used for errors?

Quoted 20 lines

+ */

xen/include/public/io/sndif.h new file +19 -0

+
+struct xensnd_req {
+    uint16_t id;
+    uint8_t operation;
+    uint8_t stream_idx;
+    uint32_t reserved;
+    union {
+        struct xensnd_open_req open;
+        struct xensnd_rw_req rw;
+        uint8_t reserved[24];
+    } op;
+};
+
+struct xensnd_resp {
+    uint16_t id;
+    uint8_t operation;
+    uint8_t stream_idx;
+    int8_t status;
+    uint8_t reserved[27];

Quoted 8 lines

xen/include/public/io/sndif.h new file +5 -0

+};
+
+DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);
+
+#endif /* __XEN_PUBLIC_IO_SNDIF_H__ */

Signature · 1 line

2.7.4

Hi, Konrad!

First of all thank you very much for the valuable comments

and your time!

The number of changes (mostly in description) is going to

be huge, so do you think I can publish something like

"RFC v16" so we can discuss the updated patch?

Quoted 10 lines

Quoted 8 lines · Oleksandr Andrushchenko

+ * Example for the frontend running in domain 5, instance of the driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ *         device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Quoted 1 line

Why do you need 'device' ?

just for clarity: the hierarchy of the sound driver would be that a device may have multiple different streams. So, from readability POV I would still have "device" in place From xenstore documentation: "Data should generally be human-readable for ease of management and debugging " I assume this also applies to the structure as well

Quoted 3 lines

Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

then one has to know that "2" stands for device. see above, I would keep "device" here

Quoted 1 line

Quoted 1 line

Quoted 6 lines · Oleksandr Andrushchenko

Hi, Konrad!

First of all thank you very much for the valuable comments

and your time!

Quoted 6 lines

The number of changes (mostly in description) is going to

be huge, so do you think I can publish something like

"RFC v16" so we can discuss the updated patch?

Konrad's call, but why you want to introduce the 'RFC' tag now? I'd just go with v16...

Quoted 12 lines · Konrad Rzeszutek Wilk

Quoted 10 lines

Quoted 8 lines · Oleksandr Andrushchenko

+ * Example for the frontend running in domain 5, instance of the driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ * device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Quoted 8 lines

Quoted 1 line

Why do you need 'device' ?

just for clarity: the hierarchy of the sound driver would be that a device may have multiple different streams. So, from readability POV I would still have "device" in place
From xenstore documentation: "Data should generally be
human-readable for ease of management and debugging " I assume this also applies to the structure as well

Perhaps:

/local/domain/<frontend_id>/device/vsnd/<drv_idx>/dev-<dev_id>/stream-<stream_idx>/...

Quoted 5 lines

Quoted 3 lines

Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

then one has to know that "2" stands for device. see above, I would keep "device" here

/local/domain/5/device/vsnd/0/dev-2/stream-0/type = "p"

Or, with no '-':

/local/domain/5/device/vsnd/0/dev2/stream0/type = "p"

Just my 2 cents...

Dario

Quoted 23 lines · Dario Faggioli

Quoted 13 lines · Konrad Rzeszutek Wilk

Quoted 12 lines

Quoted 10 lines · Oleksandr Andrushchenko

+ * Example for the frontend running in domain 5, instance of the
driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ *         device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Quoted 6 lines

Quoted 4 lines

Why do you need 'device' ?
Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

then one has to know that "2" stands for device.
see above, I would keep "device" here

  /local/domain/5/device/vsnd/0/dev-2/stream-0/type = "p"

Or, with no '-':

Quoted 3 lines

  /local/domain/5/device/vsnd/0/dev2/stream0/type = "p"

Just my 2 cents...

1. Well, the only reason I have "device" here is for clarity and consistency: sound card owns PCM devices, PCM device owns streams
We could probably have "pcm-dev" instead of "device" here, so we do not collide with xen device.

2. "dev-%d" or "dev%d", "stream-%d" or "stream%d" IMO, we already have indices employed in xenstore, e.g. "domain/5", not "domain-5" or "domain5"
So, is the PCM device in question any different from domain from this POV? To me - not, so this is why I use "device/%d"

Quoted 26 lines · Oleksandr Andrushchenko

Quoted 25 lines · Dario Faggioli

Quoted 13 lines · Konrad Rzeszutek Wilk

Quoted 12 lines

Quoted 10 lines · Oleksandr Andrushchenko

+ * Example for the frontend running in domain 5, instance of the
driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ * device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Quoted 6 lines

Quoted 4 lines

Why do you need 'device' ?
Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

then one has to know that "2" stands for device.
see above, I would keep "device" here

/local/domain/5/device/vsnd/0/dev-2/stream-0/type = "p"

Or, with no '-':

   /local/domain/5/device/vsnd/0/dev2/stream0/type = "p"

Quoted 7 lines

Quoted 1 line

Just my 2 cents...

1. Well, the only reason I have "device" here is for clarity and consistency: sound card owns PCM devices, PCM device owns streams
We could probably have "pcm-dev" instead of "device" here, so we do not collide with xen device.

Sure. Or maybe even just 'pcm' (matter of taste, to large extent).

Quoted 6 lines

2. "dev-%d" or "dev%d", "stream-%d" or "stream%d" IMO, we already have indices employed in xenstore, e.g. "domain/5", not "domain-5" or "domain5"
So, is the PCM device in question any different from domain from this POV? To me - not, so this is why I use "device/%d"

True. Well, actually, have both. For instance, blkif, when multiqueue is available are enabled, looks like this:

/local/domain/1/device/vbd/0/multi-queue-num-queues = "2" /local/domain/1/device/vbd/0/queue-0 = "" /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" /local/domain/1/device/vbd/0/queue-1 = "" /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"

So, while I after all thing I agree with you on point 1) (i.e., on having device, or pcm-dev, or pcm, the latter being my prefernce), I think it would be ok to manage streams like blkif manages queues, and hence using stream-0, stream-1, etc.

Regards,
Dario

Quoted 6 lines · Oleksandr Andrushchenko

Hi, Konrad!

First of all thank you very much for the valuable comments

and your time!

Quoted 6 lines

The number of changes (mostly in description) is going to

be huge, so do you think I can publish something like

"RFC v16" so we can discuss the updated patch?

Konrad's call, but why you want to introduce the 'RFC' tag now? I'd just go with v16...

Quoted 12 lines · Konrad Rzeszutek Wilk

Quoted 10 lines

Quoted 8 lines · Oleksandr Andrushchenko

+ * Example for the frontend running in domain 5, instance of the driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ *         device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Quoted 3 lines

Quoted 1 line

Why do you need 'device' ?

just for clarity: the hierarchy of the sound driver would be that a device may have multiple different streams.

Quoted 5 lines

So, from readability POV I would still have "device" in place From xenstore documentation: "Data should generally be human-readable for ease of management and debugging " I assume this also applies to the structure as well

Perhaps:

 /local/domain/<frontend_id>/device/vsnd/<drv_idx>/dev-<dev_id>/stream-<stream_idx>/...

Quoted 6 lines

Quoted 3 lines

Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

then one has to know that "2" stands for device. see above, I would keep "device" here

Quoted 1 line

Quoted 1 line

 /local/domain/5/device/vsnd/0/dev-2/stream-0/type = "p"

Or, with no '-':

 /local/domain/5/device/vsnd/0/dev2/stream0/type = "p"

Just my 2 cents...

Dario

Signature · 4 lines

<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

Hi, Konrad!

First of all thank you very much for the valuable comments

and your time!

The number of changes (mostly in description) is going to

be huge, so do you think I can publish something like

"RFC v16" so we can discuss the updated patch?

Quoted 7 lines

Quoted 6 lines

+ * Example for the frontend running in domain 5, instance of the driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ * device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"

Why do you need 'device' ?

just for clarity: the hierarchy of the sound driver would be that a device may have multiple different streams.

So, from readability POV I would still have "device" in place From xenstore documentation: "Data should generally be human-readable for ease of management and debugging " I assume this also applies to the structure as well

Quoted 4 lines

Could not this be:

/local/domain/5/device/vsnd/0/2/stream/0/type = "p" ?

then one has to know that "2" stands for device. see above, I would keep "device" here

Quoted 9 lines

Quoted 6 lines

+ *
+ *------------------------------- PCM settings --------------------------------
+ *
+ * Every virtualized sound frontend has set of devices and streams, each

frontend or backend?

I would think backend since this is still the backend section?

you are right, moved to frontend's section

Quoted 13 lines

Quoted 13 lines

+ * is individually configured. Part of the PCM configuration can be defined at
+ * higher level and be fully or partially re-used by the underlying layers.
+ * These configuration values are:

+ *  o number of channels (min/max)
+ *  o supported sample rates
+ *  o supported sample formats.

+ * E.g. one can define these values for the whole driver, device or stream.
+ * Every underlying layer in turn can re-define some or all of them to better
+ * fit its needs. For example, driver may define number of channels to be
+ * in [1; 8] range, and some particular stream may be limited to [1; 2] only.
+ * The rule is that the underlying layer must be a subset of the upper layer
+ * range.

Quoted 1 line

OK, so these are more of 'global ones'?

kind of, what is more they can be "global" to all the underlying levels, e.g. if device changes some of the parameters they become adopted by streams if not explicitly configured. The same is true if device changes parameters set at the card level.
This way one can easily tailor particular pieces of the system w/o writing all settings again

Quoted 9 lines

Quoted 3 lines

+ *
+ * Note: if any of the values are not defined then PV driver should use
+ * its default values instead.

How is that suppose to work? What if the PV driver by default wants to use say 314156 channels and the backend does not expose any? Can it use that? I presume it could try.. and it would fail but that hardly seems nice.

I will probably remove this sentence and the below at all. If not defined this could mean an error state

Quoted 22 lines

Quoted 3 lines

+ *
+ * channels-min
+ * Values: <uint>

uint32_t

Quoted 3 lines

+ *
+ * The minimum amount of channels that is supported.
+ * Must be at least 1. If not defined then use frontend's default.

This is odd. This whole section is for the backend, so how can the backend not have this defined?

Do you mean to say that this parameter is optional? Perhaps then say right before 'The minimum' include '(optional)'

Anyhow where do you envision this optional global value to be?

/local/domain/0/backend/vsnd/5/channels-[min|max] ?

Perhaps mention that in the start of this section:

These global values are under the backend 'vsnd' directory, as so:

Quoted 4 lines

/local/domain/0/backends/vsnd/<front-id>/channels-[min|max]

Thought I think there is probably a better way to
say this..

well, the confusion comes from the fact that I have described all this under backend's section now when I move it to the frontend's section it should make more sense

Quoted 4 lines

Quoted 3 lines

+ *
+ * channels-max
+ * Values: <uint>

uint32_t

uint8_t

Quoted 7 lines

Quoted 4 lines

+ *

+ *      The maximum amount of channels that is supported.
+ *      Must be at least <channels-min>. If not defined then use frontend's
+ *      default.

I am still having trouble understanding how the backend is suppose to use the frontend's default.

Quoted 6 lines

Perhaps you want to say:

If this value is not exposed by the backend the frontend is permitted to use its default values.

?

moved to frontend's section

Quoted 4 lines

Quoted 3 lines

+ *
+ * sample-rates
+ * Values: <list of uints>

.. of uint32_t

done

Quoted 5 lines

Quoted 3 lines

+ *
+ * List of supported sample rates separated by XENSND_LIST_SEPARATOR.
+ * If not defined then use frontend's default. Sample rates are expressed

Ahain this 'If not defined then use fronten'ds default' could be written a bit differently.

moved to frontend's section

Quoted 9 lines

Quoted 7 lines

+ * as a list of decimal values w/o any ordering requirement.
+ *
+ * sample-formats
+ * Values: <list of XENSND_PCM_FORMAT_XXX_STR>
+ *
+ * List of supported sample formats separated by XENSND_LIST_SEPARATOR.
+ * If not defined then use frontend's default.

Again, this does not sound right. The backend has no clue what the frontend defaults are.

moved to frontend's section

Quoted 4 lines

Quoted 3 lines

+ *
+ * buffer-size
+ * Values: <uint>

uint32_t

done

Quoted 11 lines

Quoted 7 lines

+ *
+ * The maximum size in octets of the buffer to allocate per stream.
+ *
+ * Example configuration:
+ *
+ * Driver configuration used by all streams:
+ * /local/domain/5/device/vsnd/0/sample-formats = "s8;u8;s16_le;s16_be"

Huh? But this is a backend value? Don't you mean:

/local/domain/0/backend/vsnd/5/sample-formats = "s8;u8;s16_le;s16_be" ?

moved to frontend's section

Quoted 2 lines

Quoted 1 line

+ * Stream overrides sample rates supported:

-EPARSE

done

Quoted 11 lines

Quoted 3 lines

+ * /local/domain/5/device/vsnd/0/device/2/stream/0/sample-rates =
+ * "8000;22050;44100;48000"

/local/domain/0/backend/vsnd/5/2/stream/0/sample-rates ="8000;22050;44100;48000"

But that is wrong as this section is about global values so they would be more like:

/local/domain/0/backend/vsnd/5/sample-rates ="8000;22050;44100;48000"

?

not anymore, as I move these to frontend's configuration

Quoted 16 lines

Quoted 8 lines

+ *
+ *----------------------- Virtual sound card settings --------------------------
+ * short-name
+ * Values: <char[32]>
+ *
+ * Short name of the virtual sound card. Optional.
+ *
+ * long-name

Quoted 8 lines

+ * Values: <char[80]>
+ *
+ * Long name of the virtual sound card. Optional.
+ *
+ * For example,
+ * /local/domain/5/device/vsnd/0/short-name = "Virtual audio"
+ * /local/domain/5/device/vsnd/0/long-name =
+ * "Virtual audio at center stack"

Quoted 8 lines

This should be inverted. That is this is on the backend side:

/local/domain/0/backend/vsnd/5/0/2/short-name = "Virtual audio"

And so on.

Also how come your example is missing the device part?

I will put a complete configuration example

Quoted 5 lines

Wait, why do you have an an device below but ... not here? Why not group them together?

That is why not have 'short-name' ,'long-name' and 'name' in the same directory?

name is for a stream; short/long for the card

Quoted 10 lines

Quoted 10 lines

+ *
+ *----------------------------- Device settings --------------------------------
+ * name
+ * Values: <char[80]>
+ *
+ * Name of the sound device within the virtual sound card. Optional.
+ *
+ * For example,
+ * /local/domain/5/device/vsnd/0/device/0/name = "General analog"

Quoted 4 lines

The example you used at start had a device value of 2. It may be better to use that here, so :

/local/domain/0/backend/vsnd/5/2/name = "General analog"

done

Quoted 12 lines

Quoted 8 lines

+ *
+ *----------------------------- Stream settings -------------------------------
+ *
+ * type
+ * Values: "p", "c"
+ *
+ * Stream type: "p" - playback stream, "c" - capture stream
+ *

Quoted 4 lines

+ *      If both capture and playback are needed then two streams need to be
+ *      defined under the same device. For example,
+ *      /local/domain/5/device/vsnd/0/device/0/stream/0/type = "p"
+ *      /local/domain/5/device/vsnd/0/device/0/stream/1/type = "c"

Quoted 7 lines

OK, but again:
/local/domain/0/backend/vsnd/5/2/0/stream/0/type = "p" /local/domain/0/backend/vsnd/5/2/0/stream/1/type = "c"

Do you want also an 'feature-version' to identify what version the backend exposes?

will add that

Quoted 8 lines

Quoted 8 lines

+ *
+ *****************************************************************************
+ * Frontend XenBus Nodes
+ *****************************************************************************
+ *
+ *----------------------- Request Transport Parameters -----------------------
+ *
+ * These are per stream.

Quoted 8 lines

.. which means they are also per device right?

So one can have something like this:

/local/domain/5/device/vsnd/2/stream/0/event-channel /local/domain/5/device/vsnd/0/stream/0/event-channel /local/domain/5/device/vsnd/2/stream/1/event-channel /local/domain/5/device/vsnd/0/stream/0/event-channel

yes, every stream has its own communication channel

Quoted 4 lines

Quoted 3 lines

+ *
+ * event-channel
+ * Values: <uint>

uint32_t

done

Quoted 7 lines

Quoted 6 lines

+ *
+ * The identifier of the Xen event channel used to signal activity
+ * in the ring buffer.
+ *
+ * ring-ref
+ * Values: <uint>

uint32_t

done

Quoted 6 lines

Quoted 5 lines

+ *
+ * The Xen grant reference granting permission for the backend to map
+ * a sole page in a single page sized ring buffer.
+ *
+ * index

Why not 'unique-id' ?

makes sense, will change

Quoted 2 lines

Quoted 1 line

+ * Values: <uint>

uint32_t

done

Quoted 5 lines

Quoted 4 lines

+ *

+ *      After stream initialization it is assigned a unique ID (within the front
+ *      driver), so every stream of the frontend can be identified by the
+ *      backend by this ID. This is not equal to stream_idx as the later is

s/stream_idx/steam-idx/

done

Quoted 2 lines

Quoted 1 line

+ * zero based within a device, but this index is contiguous within the

contingous

done

Quoted 147 lines

Quoted 134 lines

+ * driver.

+ */

xen/include/public/io/sndif.h new file +131 -0

+
+/*
+ * STATE DIAGRAMS
+ *
+ *****************************************************************************
+ *                                   Startup                                 *
+ *****************************************************************************
+ *
+ * Tool stack creates front and back state nodes with initial state
+ * XenbusStateInitialising.
+ * Tool stack creates and sets up frontend sound configuration nodes per domain.
+ *
+ * Front                                Back
+ * =================================    =====================================
+ * XenbusStateInitialising              XenbusStateInitialising
+ *                                       o Query backend device identification
+ *                                         data.
+ *                                       o Open and validate backend device.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateInitWait
+ *
+ * o Query frontend configuration
+ * o Allocate and initialize
+ *   event channels per configured
+ *   playback/capture stream.
+ * o Publish transport parameters
+ *   that will be in effect during
+ *   this connection.
+ *              |
+ *              |
+ *              V
+ * XenbusStateInitialised
+ *
+ *                                       o Query frontend transport parameters.
+ *                                       o Connect to the event channels.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateConnected
+ *
+ *  o Create and initialize OS
+ *  virtual sound device instances
+ *  as per configuration.
+ *              |
+ *              |
+ *              V
+ * XenbusStateConnected
+ *
+ *                                      XenbusStateUnknown
+ *                                      XenbusStateClosed
+ *                                      XenbusStateClosing
+ * o Remove virtual sound device
+ * o Remove event channels
+ *              |
+ *              |
+ *              V
+ * XenbusStateClosed
+ *
+ */
+
+/*
+ * PCM FORMATS
+ *
+ * XENSND_PCM_FORMAT_<format>[_<endian>]
+ *
+ * format: <S/U/F><bits> or <name>
+ *     S - signed, U - unsigned, F - float
+ *     bits - 8, 16, 24, 32
+ *     name - MU_LAW, GSM, etc.
+ *
+ * endian: <LE/BE>, may be absent
+ *     LE - Little endian, BE - Big endian
+ */
+#define XENSND_PCM_FORMAT_S8            0
+#define XENSND_PCM_FORMAT_U8            1
+#define XENSND_PCM_FORMAT_S16_LE        2
+#define XENSND_PCM_FORMAT_S16_BE        3
+#define XENSND_PCM_FORMAT_U16_LE        4
+#define XENSND_PCM_FORMAT_U16_BE        5
+#define XENSND_PCM_FORMAT_S24_LE        6
+#define XENSND_PCM_FORMAT_S24_BE        7
+#define XENSND_PCM_FORMAT_U24_LE        8
+#define XENSND_PCM_FORMAT_U24_BE        9
+#define XENSND_PCM_FORMAT_S32_LE        10
+#define XENSND_PCM_FORMAT_S32_BE        11
+#define XENSND_PCM_FORMAT_U32_LE        12
+#define XENSND_PCM_FORMAT_U32_BE        13
+#define XENSND_PCM_FORMAT_F32_LE        14 /* 4-byte float, IEEE-754 32-bit, */
+#define XENSND_PCM_FORMAT_F32_BE        15 /* range -1.0 to 1.0              */
+#define XENSND_PCM_FORMAT_F64_LE        16 /* 8-byte float, IEEE-754 64-bit, */
+#define XENSND_PCM_FORMAT_F64_BE        17 /* range -1.0 to 1.0              */
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE 18
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE 19
+#define XENSND_PCM_FORMAT_MU_LAW        20
+#define XENSND_PCM_FORMAT_A_LAW         21
+#define XENSND_PCM_FORMAT_IMA_ADPCM     22
+#define XENSND_PCM_FORMAT_MPEG          23
+#define XENSND_PCM_FORMAT_GSM           24
+
+/*
+ * REQUEST CODES.
+ */
+#define XENSND_OP_OPEN                  0
+#define XENSND_OP_CLOSE                 1
+#define XENSND_OP_READ                  2
+#define XENSND_OP_WRITE                 3
+#define XENSND_OP_SET_VOLUME            4
+#define XENSND_OP_GET_VOLUME            5
+#define XENSND_OP_MUTE                  6
+#define XENSND_OP_UNMUTE                7
+
+/*
+ * XENSTORE FIELD AND PATH NAME STRINGS, HELPERS.
+ */
+#define XENSND_DRIVER_NAME              "vsnd"
+
+#define XENSND_LIST_SEPARATOR           ";"
+/* Path entries */
+#define XENSND_PATH_DEVICE              "device"
+#define XENSND_PATH_STREAM              "stream"
+/* Field names */
+#define XENSND_FIELD_VCARD_SHORT_NAME   "short-name"
+#define XENSND_FIELD_VCARD_LONG_NAME    "long-name"
+#define XENSND_FIELD_RING_REF           "ring-ref"
+#define XENSND_FIELD_EVT_CHNL           "event-channel"
+#define XENSND_FIELD_DEVICE_NAME        "name"
+#define XENSND_FIELD_TYPE               "type"
+#define XENSND_FIELD_STREAM_INDEX       "index"
+#define XENSND_FIELD_CHANNELS_MIN       "channels-min"

xen/include/public/io/sndif.h line 367

Quoted 10 lines

xen/include/public/io/sndif.h new file +10 -0

+#define XENSND_FIELD_CHANNELS_MAX       "channels-max"
+#define XENSND_FIELD_SAMPLE_RATES       "sample-rates"
+#define XENSND_FIELD_SAMPLE_FORMATS     "sample-formats"
+#define XENSND_FIELD_BUFFER_SIZE        "buffer-size"
+
+/* Stream type field values. */
+#define XENSND_STREAM_TYPE_PLAYBACK     "p"
+#define XENSND_STREAM_TYPE_CAPTURE      "c"
+/* Sample rate max string length */
+#define XENSND_SAMPLE_RATE_MAX_LEN      6

Hm, but it is uint32_t which can be much much higher than 6.

Quoted 3 lines

4294967295

11 characters?

fixed

Quoted 4 lines

xen/include/public/io/sndif.h line 369

Quoted 2 lines

xen/include/public/io/sndif.h new file +2 -0

+/* Sample format field values */
+#define XENSND_SAMPLE_FORMAT_MAX_LEN    24

You sure? You may want to make that clear in 'sample-format' section that the maximum of a string can be 24 characters.

done

Quoted 2 lines

And also explain why 24 characters.

no particular reason, just to fit XENSND_PCM_FORMAT_???_STR do you want me to change it to something else?

Quoted 26 lines

Quoted 26 lines

xen/include/public/io/sndif.h new file +26 -0

+
+#define XENSND_PCM_FORMAT_S8_STR        "s8"
+#define XENSND_PCM_FORMAT_U8_STR        "u8"
+#define XENSND_PCM_FORMAT_S16_LE_STR    "s16_le"
+#define XENSND_PCM_FORMAT_S16_BE_STR    "s16_be"
+#define XENSND_PCM_FORMAT_U16_LE_STR    "u16_le"
+#define XENSND_PCM_FORMAT_U16_BE_STR    "u16_be"
+#define XENSND_PCM_FORMAT_S24_LE_STR    "s24_le"
+#define XENSND_PCM_FORMAT_S24_BE_STR    "s24_be"
+#define XENSND_PCM_FORMAT_U24_LE_STR    "u24_le"
+#define XENSND_PCM_FORMAT_U24_BE_STR    "u24_be"
+#define XENSND_PCM_FORMAT_S32_LE_STR    "s32_le"
+#define XENSND_PCM_FORMAT_S32_BE_STR    "s32_be"
+#define XENSND_PCM_FORMAT_U32_LE_STR    "u32_le"
+#define XENSND_PCM_FORMAT_U32_BE_STR    "u32_be"
+#define XENSND_PCM_FORMAT_F32_LE_STR    "float_le"
+#define XENSND_PCM_FORMAT_F32_BE_STR    "float_be"
+#define XENSND_PCM_FORMAT_F64_LE_STR    "float64_le"
+#define XENSND_PCM_FORMAT_F64_BE_STR    "float64_be"
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR "iec958_subframe_le"
+#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR "iec958_subframe_be"
+#define XENSND_PCM_FORMAT_MU_LAW_STR    "mu_law"
+#define XENSND_PCM_FORMAT_A_LAW_STR     "a_law"
+#define XENSND_PCM_FORMAT_IMA_ADPCM_STR "ima_adpcm"
+#define XENSND_PCM_FORMAT_MPEG_STR      "mpeg"
+#define XENSND_PCM_FORMAT_GSM_STR       "gsm"

Quoted 8 lines

xen/include/public/io/sndif.h line 402

Quoted 7 lines

xen/include/public/io/sndif.h new file +7 -0

+
+/*
+ * STATUS RETURN CODES.
+ */
+/* Operation not supported. */
+#define XENSND_RSP_NOTSUPP              (-2)
+/* Operation failed for some unspecified reason (e. g. -EIO). */

Is that the -EIO going to be exposed somewhere?

no

Quoted 2 lines

Inside of the
'struct xensnd_resp' ?