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i2c: slave-mqueue: add a slave backend to receive and queue messages

PATCH Superseded Haiyue Wang 2 participants 3 messages Mar 17, 2018 – Mar 20, 2018

Subsystems (2)
I2C subsystem host drivers I2C

v1 of 5 Superseded Latest is v5 →

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Haiyue Wang

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PATCH 1/1 i2c: slave-mqueue: add a slave backend to receive and queue messages

Some protocols over I2C are designed for bi-directional transferring messages by using I2C Master Write protocol. Like the MCTP (Management Component Transport Protocol) and IPMB (Intelligent Platform Management Bus), they both require that the userspace can receive messages from I2C dirvers under slave mode.

This new slave mqueue backend is used to receive and queue messages, it will exposes these messages to userspace by sysfs bin file.

Signed-off-by Haiyue Wang <[email protected]>
---
 Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++
 drivers/i2c/Kconfig                        |  13 ++
 drivers/i2c/Makefile                       |   1 +
 drivers/i2c/i2c-slave-mqueue.c             | 202 +++++++++++++++++++++++++++++
 4 files changed, 341 insertions(+)
 create mode 100644 Documentation/i2c/slave-mqueue-backend.rst
 create mode 100644 drivers/i2c/i2c-slave-mqueue.c
Documentation/i2c/slave-mqueue-backend.rst new file +125 -0
new file mode 100644
index 0000000..69d6437
@@ -0,0 +1,125 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Linux I2C slave message queue backend
+=====================================
+
+:Author: Haiyue Wang <[email protected]>
+
+Some protocols over I2C/SMBus are designed for bi-directional transferring
+messages by using I2C Master Write protocol. This requires that both sides
+of the communication have slave addresses.
+
+Like MCTP (Management Component Transport Protocol) and IPMB (Intelligent
+Platform Management Bus), they both require that the userspace can receive
+messages from i2c dirvers under slave mode.
+
+This I2C slave mqueue (message queue) backend is used to receive and queue
+messages from the remote i2c intelligent device; and it will add the target
+slave address (with R/W# bit is always 0) into the message at the first byte,
+so that userspace can use this byte to dispatch the messages into different
+handling modules. Also, like IPMB, the address byte is in its message format,
+it needs it to do checksum.
+
+For messages are time related, so this backend will flush the oldest message
+to queue the newest one.
+
+Link
+----
+`Intelligent Platform Management Bus
+Communications Protocol Specification
+<https://www.intel.com/content/dam/www/public/us/en/documents/product-briefs/ipmp-spec-v1.0.pdf>`_
+
+`Management Component Transport Protocol (MCTP)
+SMBus/I2C Transport Binding Specification
+<https://www.dmtf.org/sites/default/files/standards/documents/DSP0237_1.1.0.pdf>`_
+
+How to use
+----------
+For example, the I2C5 bus has slave address 0x10, bellowing command will create
+the related message queue interface:
+
+    echo slave-mqueue 0x1010 > /sys/bus/i2c/devices/i2c-5/new_device
+
+Then you can dump the messages like this:
+
+    hexdump -C /sys/bus/i2c/devices/5-1010/slave-mqueue
+
+Code Example
+------------
+*Note: call 'lseek' before 'read', this is a requirement from kernfs' design.*
+
+::
+
+  #include <sys/types.h>
+  #include <sys/stat.h>
+  #include <unistd.h>
+  #include <poll.h>
+  #include <time.h>
+  #include <fcntl.h>
+  #include <stdio.h>
+
+  int main(int argc, char *argv[])
+  {
+          int i, r;
+          struct pollfd pfd;
+          struct timespec ts;
+          unsigned char data[256];
+
+          pfd.fd = open(argv[1], O_RDONLY | O_NONBLOCK);
+          if (pfd.fd < 0)
+                  return -1;
+
+          pfd.events = POLLPRI;
+
+          while (1) {
+                  r = poll(&pfd, 1, 5000);
+
+                  if (r < 0)
+                          break;
+
+                  if (r == 0 || !(pfd.revents & POLLPRI))
+                          continue;
+
+                  lseek(pfd.fd, 0, SEEK_SET);
+                  r = read(pfd.fd, data, sizeof(data));
+                  if (r <= 0)
+                          continue;
+
+                  clock_gettime(CLOCK_MONOTONIC, &ts);
+                  printf("[%ld.%.9ld] :", ts.tv_sec, ts.tv_nsec);
+                  for (i = 0; i < r; i++)
+                          printf(" %02x", data[i]);
+                  printf("\n");
+          }
+
+          close(pfd.fd);
+
+          return 0;
+  }
+
+Result
+------
+*./a.out "/sys/bus/i2c/devices/5-1010/slave-mqueue"*
+
+::
+
+  [10183.232500449] : 20 18 c8 2c 78 01 5b
+  [10183.479358348] : 20 18 c8 2c 78 01 5b
+  [10183.726556812] : 20 18 c8 2c 78 01 5b
+  [10183.972605863] : 20 18 c8 2c 78 01 5b
+  [10184.220124772] : 20 18 c8 2c 78 01 5b
+  [10184.467764166] : 20 18 c8 2c 78 01 5b
+  [10193.233421784] : 20 18 c8 2c 7c 01 57
+  [10193.480273460] : 20 18 c8 2c 7c 01 57
+  [10193.726788733] : 20 18 c8 2c 7c 01 57
+  [10193.972781945] : 20 18 c8 2c 7c 01 57
+  [10194.220487360] : 20 18 c8 2c 7c 01 57
+  [10194.468089259] : 20 18 c8 2c 7c 01 57
+  [10203.233433099] : 20 18 c8 2c 80 01 53
+  [10203.481058715] : 20 18 c8 2c 80 01 53
+  [10203.727610472] : 20 18 c8 2c 80 01 53
+  [10203.974044856] : 20 18 c8 2c 80 01 53
+  [10204.220734634] : 20 18 c8 2c 80 01 53
+  [10204.468461664] : 20 18 c8 2c 80 01 53
+
drivers/i2c/Kconfig +13 -0
index efc3354..7053b5b 100644
@@ -118,6 +118,19 @@ if I2C_SLAVE
 config I2C_SLAVE_EEPROM
 	tristate "I2C eeprom slave driver"
 
+config I2C_SLAVE_MQUEUE
+	tristate "I2C mqueue (message queue) slave driver"
+	help
+	  Some protocols over I2C are designed for bi-directional transferring
+	  messages by using I2C Master Write protocol. This driver is used to
+	  receive and queue messages from the remote I2C device.
+
+	  Userspace can get the messages by reading sysfs file that this driver
+	  exposes.
+
+	  This support is also available as a module. If so, the module will be
+	  called i2c-slave-mqueue.
+
 endif
 
 config I2C_DEBUG_CORE
drivers/i2c/Makefile +1 -0
index 72c94c6..7ec287b 100644
@@ -16,6 +16,7 @@ obj-$(CONFIG_I2C_MUX)		+= i2c-mux.o
 obj-y				+= algos/ busses/ muxes/
 obj-$(CONFIG_I2C_STUB)		+= i2c-stub.o
 obj-$(CONFIG_I2C_SLAVE_EEPROM)	+= i2c-slave-eeprom.o
+obj-$(CONFIG_I2C_SLAVE_MQUEUE)	+= i2c-slave-mqueue.o
 
 ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
 CFLAGS_i2c-core-base.o := -Wno-deprecated-declarations
drivers/i2c/i2c-slave-mqueue.c new file +202 -0

202 lines not on this page · raw message

Signature · 1 line
2.7.4
Reviewed-by on v1 1/1
#1 lore raw
Quoted 11 lines · Haiyue Wang

Some protocols over I2C are designed for bi-directional transferring messages by using I2C Master Write protocol. Like the MCTP (Management Component Transport Protocol) and IPMB (Intelligent Platform Management
Bus), they both require that the userspace can receive messages from I2C dirvers under slave mode.

This new slave mqueue backend is used to receive and queue messages, it
will exposes these messages to userspace by sysfs bin file.

Wolfram, I'm not sure this is the best approach, though I can't propose anything else right now.

If you are satisfied with it, I give a formal

Reviewed-by Andy Shevchenko <[email protected]>
Quoted 414 lines
Signed-off-by Haiyue Wang <[email protected]>
---
 Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++
 drivers/i2c/Kconfig                        |  13 ++
 drivers/i2c/Makefile                       |   1 +
 drivers/i2c/i2c-slave-mqueue.c             | 202
+++++++++++++++++++++++++++++
 4 files changed, 341 insertions(+)
 create mode 100644 Documentation/i2c/slave-mqueue-backend.rst
 create mode 100644 drivers/i2c/i2c-slave-mqueue.c
Documentation/i2c/slave-mqueue-backend.rst new file +9 -0
new file mode 100644
index 0000000..69d6437
@@ -0,0 +1,125 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Linux I2C slave message queue backend
+=====================================
+
+:Author: Haiyue Wang <[email protected]>
+
+Some protocols over I2C/SMBus are designed for bi-directional

transferring
+messages by using I2C Master Write protocol. This requires that both sides

Documentation/i2c/slave-mqueue-backend.rst new file +3 -0
+of the communication have slave addresses.
+
+Like MCTP (Management Component Transport Protocol) and IPMB

(Intelligent
+Platform Management Bus), they both require that the userspace can receive

Documentation/i2c/slave-mqueue-backend.rst new file +3 -0
+messages from i2c dirvers under slave mode.
+
+This I2C slave mqueue (message queue) backend is used to receive and

queue
+messages from the remote i2c intelligent device; and it will add the target
+slave address (with R/W# bit is always 0) into the message at the first byte,
+so that userspace can use this byte to dispatch the messages into different
+handling modules. Also, like IPMB, the address byte is in its message format,

Documentation/i2c/slave-mqueue-backend.rst new file +3 -0
+it needs it to do checksum.
+
+For messages are time related, so this backend will flush the oldest

message

Documentation/i2c/slave-mqueue-backend.rst new file +11 -1
+to queue the newest one.
+
+Link
+----
+`Intelligent Platform Management Bus
+Communications Protocol Specification
+<https://www.intel.com/content/dam/www/public/us/en/documents/product
-briefs/ipmp-spec-v1.0.pdf>`_
+
+`Management Component Transport Protocol (MCTP)
+SMBus/I2C Transport Binding Specification
+<https://www.dmtf.org/sites/default/files/standards/documents/DSP0237

_1.1.0.pdf>`_

Documentation/i2c/slave-mqueue-backend.rst new file +4 -0
+
+How to use
+----------
+For example, the I2C5 bus has slave address 0x10, bellowing command

will create

Documentation/i2c/slave-mqueue-backend.rst new file +11 -0
+the related message queue interface:
+
+    echo slave-mqueue 0x1010 > /sys/bus/i2c/devices/i2c-5/new_device
+
+Then you can dump the messages like this:
+
+    hexdump -C /sys/bus/i2c/devices/5-1010/slave-mqueue
+
+Code Example
+------------
+*Note: call 'lseek' before 'read', this is a requirement from kernfs'

design.*

Documentation/i2c/slave-mqueue-backend.rst new file +75 -0
+
+::
+
+  #include <sys/types.h>
+  #include <sys/stat.h>
+  #include <unistd.h>
+  #include <poll.h>
+  #include <time.h>
+  #include <fcntl.h>
+  #include <stdio.h>
+
+  int main(int argc, char *argv[])
+  {
+          int i, r;
+          struct pollfd pfd;
+          struct timespec ts;
+          unsigned char data[256];
+
+          pfd.fd = open(argv[1], O_RDONLY | O_NONBLOCK);
+          if (pfd.fd < 0)
+                  return -1;
+
+          pfd.events = POLLPRI;
+
+          while (1) {
+                  r = poll(&pfd, 1, 5000);
+
+                  if (r < 0)
+                          break;
+
+                  if (r == 0 || !(pfd.revents & POLLPRI))
+                          continue;
+
+                  lseek(pfd.fd, 0, SEEK_SET);
+                  r = read(pfd.fd, data, sizeof(data));
+                  if (r <= 0)
+                          continue;
+
+                  clock_gettime(CLOCK_MONOTONIC, &ts);
+                  printf("[%ld.%.9ld] :", ts.tv_sec, ts.tv_nsec);
+                  for (i = 0; i < r; i++)
+                          printf(" %02x", data[i]);
+                  printf("\n");
+          }
+
+          close(pfd.fd);
+
+          return 0;
+  }
+
+Result
+------
+*./a.out "/sys/bus/i2c/devices/5-1010/slave-mqueue"*
+
+::
+
+  [10183.232500449] : 20 18 c8 2c 78 01 5b
+  [10183.479358348] : 20 18 c8 2c 78 01 5b
+  [10183.726556812] : 20 18 c8 2c 78 01 5b
+  [10183.972605863] : 20 18 c8 2c 78 01 5b
+  [10184.220124772] : 20 18 c8 2c 78 01 5b
+  [10184.467764166] : 20 18 c8 2c 78 01 5b
+  [10193.233421784] : 20 18 c8 2c 7c 01 57
+  [10193.480273460] : 20 18 c8 2c 7c 01 57
+  [10193.726788733] : 20 18 c8 2c 7c 01 57
+  [10193.972781945] : 20 18 c8 2c 7c 01 57
+  [10194.220487360] : 20 18 c8 2c 7c 01 57
+  [10194.468089259] : 20 18 c8 2c 7c 01 57
+  [10203.233433099] : 20 18 c8 2c 80 01 53
+  [10203.481058715] : 20 18 c8 2c 80 01 53
+  [10203.727610472] : 20 18 c8 2c 80 01 53
+  [10203.974044856] : 20 18 c8 2c 80 01 53
+  [10204.220734634] : 20 18 c8 2c 80 01 53
+  [10204.468461664] : 20 18 c8 2c 80 01 53
+
drivers/i2c/Kconfig +4 -0
index efc3354..7053b5b 100644
@@ -118,6 +118,19 @@ if I2C_SLAVE
 config I2C_SLAVE_EEPROM
 	tristate "I2C eeprom slave driver"
 
+config I2C_SLAVE_MQUEUE
+	tristate "I2C mqueue (message queue) slave driver"
+	help
+	  Some protocols over I2C are designed for bi-directional

transferring

drivers/i2c/Kconfig +1 -0
+	  messages by using I2C Master Write protocol. This driver is

used to

drivers/i2c/Kconfig +3 -0
+	  receive and queue messages from the remote I2C device.
+
+	  Userspace can get the messages by reading sysfs file that

this driver

drivers/i2c/Kconfig +3 -0
+	  exposes.
+
+	  This support is also available as a module. If so, the

module will be

drivers/i2c/Kconfig +2 -0
+	  called i2c-slave-mqueue.
+
 endif
 
 config I2C_DEBUG_CORE
drivers/i2c/Makefile +1 -0
index 72c94c6..7ec287b 100644
@@ -16,6 +16,7 @@ obj-$(CONFIG_I2C_MUX)		+= i2c-mux.o
 obj-y				+= algos/ busses/ muxes/
 obj-$(CONFIG_I2C_STUB)		+= i2c-stub.o
 obj-$(CONFIG_I2C_SLAVE_EEPROM)	+= i2c-slave-eeprom.o
+obj-$(CONFIG_I2C_SLAVE_MQUEUE)	+= i2c-slave-mqueue.o
 
 ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
 CFLAGS_i2c-core-base.o := -Wno-deprecated-declarations
drivers/i2c/i2c-slave- renamed from drivers/i2c/i2c-slave-mqueue.c +0 -0

mqueue.c
new file mode 100644
index 0000000..a486e85

drivers/i2c/i2c-slave-mqueue.c new file +25 -0
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 - 2018, Intel Corporation.
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+
+#define MQ_MSGBUF_SIZE		128
+#define MQ_QUEUE_SIZE		32
+#define MQ_QUEUE_NEXT(x)	(((x) + 1) & (MQ_QUEUE_SIZE - 1))
+
+struct mq_msg {
+	int	len;
+	u8	*buf;
+};
+
+struct mq_queue {
+	struct bin_attribute	bin;
+	struct kernfs_node	*kn;
+
+	spinlock_t		lock; /* spinlock for queue index

handling */

drivers/i2c/i2c-slave-mqueue.c new file +5 -0
+	int			in;
+	int			out;
+
+	struct mq_msg		*curr;
+	int			truncated; /* drop current if

truncated */

drivers/i2c/i2c-slave-mqueue.c new file +5 -0
+	struct mq_msg		queue[MQ_QUEUE_SIZE];
+};
+
+static int i2c_slave_mqueue_callback(struct i2c_client *client,
+				     enum i2c_slave_event event, u8

*val)

drivers/i2c/i2c-slave-mqueue.c new file +18 -0
+{
+	struct mq_queue *mq = i2c_get_clientdata(client);
+	struct mq_msg *msg = mq->curr;
+	int ret = 0;
+
+	switch (event) {
+	case I2C_SLAVE_WRITE_REQUESTED:
+		mq->truncated = 0;
+
+		msg->len = 1;
+		msg->buf[0] = client->addr << 1;
+		break;
+
+	case I2C_SLAVE_WRITE_RECEIVED:
+		if (msg->len < MQ_MSGBUF_SIZE) {
+			msg->buf[msg->len++] = *val;
+		} else {
+			dev_err(&client->dev, "message is

truncated!\n");

drivers/i2c/i2c-slave-mqueue.c new file +33 -0
+			mq->truncated = 1;
+			ret = -EINVAL;
+		}
+		break;
+
+	case I2C_SLAVE_STOP:
+		if (unlikely(mq->truncated))
+			break;
+
+		spin_lock(&mq->lock);
+		mq->in = MQ_QUEUE_NEXT(mq->in);
+		mq->curr = &mq->queue[mq->in];
+
+		/* Flush the oldest message */
+		if (mq->out == mq->in)
+			mq->out = MQ_QUEUE_NEXT(mq->out);
+		spin_unlock(&mq->lock);
+
+		kernfs_notify(mq->kn);
+		break;
+
+	default:
+		*val = 0xFF;
+		break;
+	}
+
+	return ret;
+}
+
+static ssize_t i2c_slave_mqueue_bin_read(struct file *filp,
+					 struct kobject *kobj,
+					 struct bin_attribute *attr,
+					 char *buf, loff_t pos,

size_t count)

drivers/i2c/i2c-slave-mqueue.c new file +8 -0
+{
+	struct mq_queue *mq;
+	struct mq_msg *msg;
+	unsigned long flags;
+	bool more = false;
+	ssize_t ret = 0;
+
+	mq = dev_get_drvdata(container_of(kobj, struct device,

kobj));

drivers/i2c/i2c-slave-mqueue.c new file +62 -0
+
+	spin_lock_irqsave(&mq->lock, flags);
+	if (mq->out != mq->in) {
+		msg = &mq->queue[mq->out];
+
+		if (msg->len <= count) {
+			ret = msg->len;
+			memcpy(buf, msg->buf, ret);
+		} else {
+			ret = -EOVERFLOW; /* Drop this HUGE one. */
+		}
+
+		mq->out = MQ_QUEUE_NEXT(mq->out);
+		if (mq->out != mq->in)
+			more = true;
+	}
+	spin_unlock_irqrestore(&mq->lock, flags);
+
+	if (more)
+		kernfs_notify(mq->kn);
+
+	return ret;
+}
+
+static int i2c_slave_mqueue_probe(struct i2c_client *client,
+				  const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct mq_queue *mq;
+	int ret, i;
+	void *buf;
+
+	mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL);
+	if (!mq)
+		return -ENOMEM;
+
+	BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE));
+
+	buf = devm_kmalloc_array(dev, MQ_QUEUE_SIZE, MQ_MSGBUF_SIZE,
+				 GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	for (i = 0; i < MQ_QUEUE_SIZE; i++)
+		mq->queue[i].buf = buf + i * MQ_MSGBUF_SIZE;
+
+	i2c_set_clientdata(client, mq);
+
+	spin_lock_init(&mq->lock);
+	mq->curr = &mq->queue[0];
+
+	sysfs_bin_attr_init(&mq->bin);
+	mq->bin.attr.name = "slave-mqueue";
+	mq->bin.attr.mode = 0400;
+	mq->bin.read = i2c_slave_mqueue_bin_read;
+	mq->bin.size = MQ_MSGBUF_SIZE * MQ_QUEUE_SIZE;
+
+	ret = sysfs_create_bin_file(&dev->kobj, &mq->bin);
+	if (ret)
+		return ret;
+
+	mq->kn = kernfs_find_and_get(dev->kobj.sd, mq-
Quoted 1 line

bin.attr.name);

drivers/i2c/i2c-slave-mqueue.c new file +46 -0
+	if (!mq->kn) {
+		sysfs_remove_bin_file(&dev->kobj, &mq->bin);
+		return -EFAULT;
+	}
+
+	ret = i2c_slave_register(client, i2c_slave_mqueue_callback);
+	if (ret) {
+		kernfs_put(mq->kn);
+		sysfs_remove_bin_file(&dev->kobj, &mq->bin);
+		return ret;
+	}
+
+	return 0;
+};
+
+static int i2c_slave_mqueue_remove(struct i2c_client *client)
+{
+	struct mq_queue *mq = i2c_get_clientdata(client);
+
+	i2c_slave_unregister(client);
+
+	kernfs_put(mq->kn);
+	sysfs_remove_bin_file(&client->dev.kobj, &mq->bin);
+
+	return 0;
+}
+
+static const struct i2c_device_id i2c_slave_mqueue_id[] = {
+	{ "slave-mqueue", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
+
+static struct i2c_driver i2c_slave_mqueue_driver = {
+	.driver = {
+		.name	= "i2c-slave-mqueue",
+	},
+	.probe		= i2c_slave_mqueue_probe,
+	.remove		= i2c_slave_mqueue_remove,
+	.id_table	= i2c_slave_mqueue_id,
+};
+module_i2c_driver(i2c_slave_mqueue_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Haiyue Wang <[email protected]>");
+MODULE_DESCRIPTION("I2C slave mode for receiving and queuing

messages");

Signature · 2 lines
Andy Shevchenko <[email protected]>
Intel Finland Oy
author
#2 lore raw

Thanks, Andy.

Hi Wolfram,

Let me introduce some development background, it is used for OpenBMC project,

which belongs to the Linux Foundation now (https://www.linuxfoundation.org/blog/openbmc-project-community-comes-together-at-the-linux-foundation-to-define-open-source-implementation-of-bmc-firmware-stack/).

1. *https://goo.gl/WgvPFi*

*** <https://goo.gl/WgvPFi>***https://lists.ozlabs.org/pipermail/openbmc/2018-January/010493.html* <https://goo.gl/WgvPFi>*

**

*IPMI is embedded within IPMB (similar to KCS, BT?)*

*

*

Who started, who responded to messages

*

We need a kernel interface for handling a multi-master slave

*

Dell has a non-standard i2c IPMB interface

o

Kernel maintains table of outstanding commands

*

Brendan suggests we need a kernel driver for doing both MCTP and IPMB

*

We can’t do them both in usersland as MCTP makes extensions to SMBUS in order to allow arbitration. Problematic extension is the “MCTP fairness arbitration”. Requires the i2c controllers on the bus (masters/slaves) to observe the line for a certain period of time in order to see who is using the line. There’s no userspace API for this, and it the timing requirements are tight

*

Slave mode is not yet exposed to the user

*

As we don’t have a userspace interface, it makes sense to add a new one

*

BR,
Haiyue

Quoted 433 lines · Andy Shevchenko
Quoted 11 lines · Haiyue Wang

Some protocols over I2C are designed for bi-directional transferring messages by using I2C Master Write protocol. Like the MCTP (Management Component Transport Protocol) and IPMB (Intelligent Platform Management
Bus), they both require that the userspace can receive messages from I2C dirvers under slave mode.

This new slave mqueue backend is used to receive and queue messages, it
will exposes these messages to userspace by sysfs bin file.

Wolfram, I'm not sure this is the best approach, though I can't propose anything else right now.

If you are satisfied with it, I give a formal

Reviewed-by Andy Shevchenko <[email protected]>
Quoted 414 lines
Signed-off-by Haiyue Wang <[email protected]>
---
  Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++
  drivers/i2c/Kconfig                        |  13 ++
  drivers/i2c/Makefile                       |   1 +
  drivers/i2c/i2c-slave-mqueue.c             | 202
+++++++++++++++++++++++++++++
  4 files changed, 341 insertions(+)

create mode 100644 Documentation/i2c/slave-mqueue-backend.rst create mode 100644 drivers/i2c/i2c-slave-mqueue.c

Documentation/i2c/slave-mqueue-backend.rst new file +9 -0
new file mode 100644
index 0000000..69d6437
@@ -0,0 +1,125 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Linux I2C slave message queue backend
+=====================================
+
+:Author: Haiyue Wang <[email protected]>
+
+Some protocols over I2C/SMBus are designed for bi-directional

transferring
+messages by using I2C Master Write protocol. This requires that both sides

Documentation/i2c/slave-mqueue-backend.rst new file +3 -0
+of the communication have slave addresses.
+
+Like MCTP (Management Component Transport Protocol) and IPMB

(Intelligent
+Platform Management Bus), they both require that the userspace can receive

Documentation/i2c/slave-mqueue-backend.rst new file +3 -0
+messages from i2c dirvers under slave mode.
+
+This I2C slave mqueue (message queue) backend is used to receive and

queue
+messages from the remote i2c intelligent device; and it will add the target
+slave address (with R/W# bit is always 0) into the message at the first byte,
+so that userspace can use this byte to dispatch the messages into different
+handling modules. Also, like IPMB, the address byte is in its message format,

Documentation/i2c/slave-mqueue-backend.rst new file +3 -0
+it needs it to do checksum.
+
+For messages are time related, so this backend will flush the oldest

message

Documentation/i2c/slave-mqueue-backend.rst new file +11 -1
+to queue the newest one.
+
+Link
+----
+`Intelligent Platform Management Bus
+Communications Protocol Specification
+<https://www.intel.com/content/dam/www/public/us/en/documents/product
-briefs/ipmp-spec-v1.0.pdf>`_
+
+`Management Component Transport Protocol (MCTP)
+SMBus/I2C Transport Binding Specification
+<https://www.dmtf.org/sites/default/files/standards/documents/DSP0237

_1.1.0.pdf>`_

Documentation/i2c/slave-mqueue-backend.rst new file +4 -0
+
+How to use
+----------
+For example, the I2C5 bus has slave address 0x10, bellowing command

will create

Documentation/i2c/slave-mqueue-backend.rst new file +11 -0
+the related message queue interface:
+
+    echo slave-mqueue 0x1010 > /sys/bus/i2c/devices/i2c-5/new_device
+
+Then you can dump the messages like this:
+
+    hexdump -C /sys/bus/i2c/devices/5-1010/slave-mqueue
+
+Code Example
+------------
+*Note: call 'lseek' before 'read', this is a requirement from kernfs'

design.*

Documentation/i2c/slave-mqueue-backend.rst new file +75 -0
+
+::
+
+  #include <sys/types.h>
+  #include <sys/stat.h>
+  #include <unistd.h>
+  #include <poll.h>
+  #include <time.h>
+  #include <fcntl.h>
+  #include <stdio.h>
+
+  int main(int argc, char *argv[])
+  {
+          int i, r;
+          struct pollfd pfd;
+          struct timespec ts;
+          unsigned char data[256];
+
+          pfd.fd = open(argv[1], O_RDONLY | O_NONBLOCK);
+          if (pfd.fd < 0)
+                  return -1;
+
+          pfd.events = POLLPRI;
+
+          while (1) {
+                  r = poll(&pfd, 1, 5000);
+
+                  if (r < 0)
+                          break;
+
+                  if (r == 0 || !(pfd.revents & POLLPRI))
+                          continue;
+
+                  lseek(pfd.fd, 0, SEEK_SET);
+                  r = read(pfd.fd, data, sizeof(data));
+                  if (r <= 0)
+                          continue;
+
+                  clock_gettime(CLOCK_MONOTONIC, &ts);
+                  printf("[%ld.%.9ld] :", ts.tv_sec, ts.tv_nsec);
+                  for (i = 0; i < r; i++)
+                          printf(" %02x", data[i]);
+                  printf("\n");
+          }
+
+          close(pfd.fd);
+
+          return 0;
+  }
+
+Result
+------
+*./a.out "/sys/bus/i2c/devices/5-1010/slave-mqueue"*
+
+::
+
+  [10183.232500449] : 20 18 c8 2c 78 01 5b
+  [10183.479358348] : 20 18 c8 2c 78 01 5b
+  [10183.726556812] : 20 18 c8 2c 78 01 5b
+  [10183.972605863] : 20 18 c8 2c 78 01 5b
+  [10184.220124772] : 20 18 c8 2c 78 01 5b
+  [10184.467764166] : 20 18 c8 2c 78 01 5b
+  [10193.233421784] : 20 18 c8 2c 7c 01 57
+  [10193.480273460] : 20 18 c8 2c 7c 01 57
+  [10193.726788733] : 20 18 c8 2c 7c 01 57
+  [10193.972781945] : 20 18 c8 2c 7c 01 57
+  [10194.220487360] : 20 18 c8 2c 7c 01 57
+  [10194.468089259] : 20 18 c8 2c 7c 01 57
+  [10203.233433099] : 20 18 c8 2c 80 01 53
+  [10203.481058715] : 20 18 c8 2c 80 01 53
+  [10203.727610472] : 20 18 c8 2c 80 01 53
+  [10203.974044856] : 20 18 c8 2c 80 01 53
+  [10204.220734634] : 20 18 c8 2c 80 01 53
+  [10204.468461664] : 20 18 c8 2c 80 01 53
+
drivers/i2c/Kconfig +4 -0
index efc3354..7053b5b 100644
@@ -118,6 +118,19 @@ if I2C_SLAVE
  config I2C_SLAVE_EEPROM
  	tristate "I2C eeprom slave driver"
 
+config I2C_SLAVE_MQUEUE
+	tristate "I2C mqueue (message queue) slave driver"
+	help
+	  Some protocols over I2C are designed for bi-directional

transferring

drivers/i2c/Kconfig +1 -0
+	  messages by using I2C Master Write protocol. This driver is

used to

drivers/i2c/Kconfig +3 -0
+	  receive and queue messages from the remote I2C device.
+
+	  Userspace can get the messages by reading sysfs file that

this driver

drivers/i2c/Kconfig +3 -0
+	  exposes.
+
+	  This support is also available as a module. If so, the

module will be

drivers/i2c/Kconfig +2 -0
+	  called i2c-slave-mqueue.
+
  endif
 
  config I2C_DEBUG_CORE
drivers/i2c/Makefile +1 -0
index 72c94c6..7ec287b 100644
@@ -16,6 +16,7 @@ obj-$(CONFIG_I2C_MUX)		+= i2c-mux.o
  obj-y				+= algos/ busses/ muxes/
  obj-$(CONFIG_I2C_STUB)		+= i2c-stub.o
  obj-$(CONFIG_I2C_SLAVE_EEPROM)	+= i2c-slave-eeprom.o
+obj-$(CONFIG_I2C_SLAVE_MQUEUE)	+= i2c-slave-mqueue.o
 
  ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
  CFLAGS_i2c-core-base.o := -Wno-deprecated-declarations
drivers/i2c/i2c-slave- renamed from drivers/i2c/i2c-slave-mqueue.c +0 -0

mqueue.c
new file mode 100644
index 0000000..a486e85

drivers/i2c/i2c-slave-mqueue.c new file +25 -0
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 - 2018, Intel Corporation.
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+
+#define MQ_MSGBUF_SIZE		128
+#define MQ_QUEUE_SIZE		32
+#define MQ_QUEUE_NEXT(x)	(((x) + 1) & (MQ_QUEUE_SIZE - 1))
+
+struct mq_msg {
+	int	len;
+	u8	*buf;
+};
+
+struct mq_queue {
+	struct bin_attribute	bin;
+	struct kernfs_node	*kn;
+
+	spinlock_t		lock; /* spinlock for queue index

handling */

drivers/i2c/i2c-slave-mqueue.c new file +5 -0
+	int			in;
+	int			out;
+
+	struct mq_msg		*curr;
+	int			truncated; /* drop current if

truncated */

drivers/i2c/i2c-slave-mqueue.c new file +5 -0
+	struct mq_msg		queue[MQ_QUEUE_SIZE];
+};
+
+static int i2c_slave_mqueue_callback(struct i2c_client *client,
+				     enum i2c_slave_event event, u8

*val)

drivers/i2c/i2c-slave-mqueue.c new file +18 -0
+{
+	struct mq_queue *mq = i2c_get_clientdata(client);
+	struct mq_msg *msg = mq->curr;
+	int ret = 0;
+
+	switch (event) {
+	case I2C_SLAVE_WRITE_REQUESTED:
+		mq->truncated = 0;
+
+		msg->len = 1;
+		msg->buf[0] = client->addr << 1;
+		break;
+
+	case I2C_SLAVE_WRITE_RECEIVED:
+		if (msg->len < MQ_MSGBUF_SIZE) {
+			msg->buf[msg->len++] = *val;
+		} else {
+			dev_err(&client->dev, "message is

truncated!\n");

drivers/i2c/i2c-slave-mqueue.c new file +33 -0
+			mq->truncated = 1;
+			ret = -EINVAL;
+		}
+		break;
+
+	case I2C_SLAVE_STOP:
+		if (unlikely(mq->truncated))
+			break;
+
+		spin_lock(&mq->lock);
+		mq->in = MQ_QUEUE_NEXT(mq->in);
+		mq->curr = &mq->queue[mq->in];
+
+		/* Flush the oldest message */
+		if (mq->out == mq->in)
+			mq->out = MQ_QUEUE_NEXT(mq->out);
+		spin_unlock(&mq->lock);
+
+		kernfs_notify(mq->kn);
+		break;
+
+	default:
+		*val = 0xFF;
+		break;
+	}
+
+	return ret;
+}
+
+static ssize_t i2c_slave_mqueue_bin_read(struct file *filp,
+					 struct kobject *kobj,
+					 struct bin_attribute *attr,
+					 char *buf, loff_t pos,

size_t count)

drivers/i2c/i2c-slave-mqueue.c new file +8 -0
+{
+	struct mq_queue *mq;
+	struct mq_msg *msg;
+	unsigned long flags;
+	bool more = false;
+	ssize_t ret = 0;
+
+	mq = dev_get_drvdata(container_of(kobj, struct device,

kobj));

drivers/i2c/i2c-slave-mqueue.c new file +62 -0
+
+	spin_lock_irqsave(&mq->lock, flags);
+	if (mq->out != mq->in) {
+		msg = &mq->queue[mq->out];
+
+		if (msg->len <= count) {
+			ret = msg->len;
+			memcpy(buf, msg->buf, ret);
+		} else {
+			ret = -EOVERFLOW; /* Drop this HUGE one. */
+		}
+
+		mq->out = MQ_QUEUE_NEXT(mq->out);
+		if (mq->out != mq->in)
+			more = true;
+	}
+	spin_unlock_irqrestore(&mq->lock, flags);
+
+	if (more)
+		kernfs_notify(mq->kn);
+
+	return ret;
+}
+
+static int i2c_slave_mqueue_probe(struct i2c_client *client,
+				  const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct mq_queue *mq;
+	int ret, i;
+	void *buf;
+
+	mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL);
+	if (!mq)
+		return -ENOMEM;
+
+	BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE));
+
+	buf = devm_kmalloc_array(dev, MQ_QUEUE_SIZE, MQ_MSGBUF_SIZE,
+				 GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	for (i = 0; i < MQ_QUEUE_SIZE; i++)
+		mq->queue[i].buf = buf + i * MQ_MSGBUF_SIZE;
+
+	i2c_set_clientdata(client, mq);
+
+	spin_lock_init(&mq->lock);
+	mq->curr = &mq->queue[0];
+
+	sysfs_bin_attr_init(&mq->bin);
+	mq->bin.attr.name = "slave-mqueue";
+	mq->bin.attr.mode = 0400;
+	mq->bin.read = i2c_slave_mqueue_bin_read;
+	mq->bin.size = MQ_MSGBUF_SIZE * MQ_QUEUE_SIZE;
+
+	ret = sysfs_create_bin_file(&dev->kobj, &mq->bin);
+	if (ret)
+		return ret;
+
+	mq->kn = kernfs_find_and_get(dev->kobj.sd, mq-
Quoted 1 line

bin.attr.name);

drivers/i2c/i2c-slave-mqueue.c new file +46 -0
+	if (!mq->kn) {
+		sysfs_remove_bin_file(&dev->kobj, &mq->bin);
+		return -EFAULT;
+	}
+
+	ret = i2c_slave_register(client, i2c_slave_mqueue_callback);
+	if (ret) {
+		kernfs_put(mq->kn);
+		sysfs_remove_bin_file(&dev->kobj, &mq->bin);
+		return ret;
+	}
+
+	return 0;
+};
+
+static int i2c_slave_mqueue_remove(struct i2c_client *client)
+{
+	struct mq_queue *mq = i2c_get_clientdata(client);
+
+	i2c_slave_unregister(client);
+
+	kernfs_put(mq->kn);
+	sysfs_remove_bin_file(&client->dev.kobj, &mq->bin);
+
+	return 0;
+}
+
+static const struct i2c_device_id i2c_slave_mqueue_id[] = {
+	{ "slave-mqueue", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
+
+static struct i2c_driver i2c_slave_mqueue_driver = {
+	.driver = {
+		.name	= "i2c-slave-mqueue",
+	},
+	.probe		= i2c_slave_mqueue_probe,
+	.remove		= i2c_slave_mqueue_remove,
+	.id_table	= i2c_slave_mqueue_id,
+};
+module_i2c_driver(i2c_slave_mqueue_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Haiyue Wang <[email protected]>");
+MODULE_DESCRIPTION("I2C slave mode for receiving and queuing

messages");