cameraif: add ABI for para-virtual camera

From: Oleksandr Andrushchenko <[email protected]>

Hello!

At the moment Xen [1] already supports some virtual multimedia features [2] such as virtual display, sound. It supports keyboards, pointers and multi-touch devices all allowing Xen to be used in automotive appliances, In-Vehicle Infotainment (IVI) systems and many more.

Frontend implementation is available at [3] and the corresponding backend at [4]. These are work in progress, but frontend already passes v4l2-compliance test for V4L2 drivers. libxl preliminary changes are available at [5].

This work adds a new Xen para-virtualized protocol for a virtual camera device which extends multimedia capabilities of Xen even
farther: video conferencing, IVI, high definition maps etc.

The initial goal is to support most needed functionality with the final idea to make it possible to extend the protocol if need be:

1. Provide means for base virtual device configuration:
- pixel formats
- resolutions
- frame rates
2. Support basic camera controls:
- contrast
- brightness
- hue
- saturation
3. Support streaming control

I would like to thank Hans Verkuil <[email protected]> for valuable comments and help.

Thank you,
Oleksandr Andrushchenko

Changes since v5:
=================

1. Minor cleanup of the XENCAMERA_OP_BUF_REQUEST description

Changes since v4:
=================

1. Removed unused XENCAMERA_EVT_CFG_FLG_RESOL flag
2. Re-worded a bit description for num_buffers

Changes since v3:
=================

1. Add trimming example for short FOURCC labels, e.g. Y16 and Y16-BE
2. Remove from XENCAMERA_OP_CONFIG_XXX requests colorspace, xfer_func, ycbcr_enc, quantization and move those into the corresponding response
3. Extend description of XENCAMERA_OP_BUF_REQUEST.num_bufs: limit to maximum buffers and num_bufs == 0 case
4. Extend decription of XENCAMERA_OP_BUF_CREATE.index and specify its range
5. Make XENCAMERA_EVT_FRAME_AVAIL.seq_num 32-bit instead of 64-bit

Changes since v2:
=================

1. Add "max-buffers" frontend configuration entry, e.g.
the maximum number of camera buffers a frontend may use.
2. Add big-endian pixel-format support:
- "formats" configuration string length changed from 4 to 7 octets, so we can also manage BE pixel-formats
- add corresponding comments to FOURCC mappings description
3. New commands added to the protocol and documented:
- XENCAMERA_OP_CONFIG_VALIDATE
- XENCAMERA_OP_FRAME_RATE_SET
- XENCAMERA_OP_BUF_GET_LAYOUT
4.-Add defaults for colorspace, xfer, ycbcr_enc and quantization
5. Remove XENCAMERA_EVT_CONFIG_CHANGE event
6. Move plane offsets to XENCAMERA_OP_BUF_REQUEST as offsets required for the frontend might not be known at the configuration time
7. Clean up and address comments to v2 of the protocol

Changes since v1:
=================

1. Added XenStore entries:
- frame-rates
2. Do not require the FOURCC code in XenStore to be upper case only
3. Added/changed command set:
- configuration get/set
- buffer queue/dequeue
- control get
4. Added control flags, e.g. read-only etc.
5. Added colorspace configuration support, relevant constants
6. Added events:
- configuration change
- control change
7. Changed control values to 64-bit
8. Added sequence number to frame avail event
9. Coding style cleanup

[1] https://www.xenproject.org/
[2] https://xenbits.xen.org/gitweb/?p=xen.git;a=tree;f=xen/include/public/io
[3] https://github.com/andr2000/linux/tree/camera_front_v1/drivers/media/xen
[4] https://github.com/andr2000/camera_be
[5] https://github.com/andr2000/xen/tree/vcamera

Oleksandr Andrushchenko (1):
cameraif: add ABI for para-virtual camera

 xen/include/public/io/cameraif.h | 1374 ++++++++++++++++++++++++++++++
 1 file changed, 1374 insertions(+)
 create mode 100644 xen/include/public/io/cameraif.h

2.21.0