[PATCHv7 1/3] dt-bindings: i2c: document bindings for i2c-slave-mqueue

[PATCHv7 1/3] dt-bindings: i2c: document bindings for i2c-slave-mqueue

[Eduardo Valentin]

Document the i2c-slave-mqueue binding by adding
descriptor, required properties, and example.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-i2c@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <eduval@amazon.com>
---

Changes from V6 to V7:
- none

 .../bindings/i2c/i2c-slave-mqueue.txt         | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt

diff --git a/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt b/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
new file mode 100644
index 000000000000..eb1881a4fc0e
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
@@ -0,0 +1,34 @@
+===============================================
+Device Tree for I2C slave message queue backend
+===============================================
+
+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.
+
+This I2C slave mqueue (message queue) 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.
+
+Links
+----
+`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>`_
+
+Required Properties:
+- compatible		: should be "i2c-slave-mqueue"
+- reg			: slave address
+
+Example:
+
+i2c {
+	slave_mqueue: i2c-slave-mqueue {
+		compatible = "i2c-slave-mqueue";
+		reg = <0x10>;
+	};
+};
-- 
2.21.0

[PATCHv7 2/3] i2c: slave-mqueue: add a slave backend to receive and queue messages

[Eduardo Valentin]

From: Haiyue Wang <haiyue.wang@linux.intel.com>

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.

Note: DT interface and a couple of minor fixes here and there
by Eduardo, so I kept the original authorship here.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: linux-i2c@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Signed-off-by: Eduardo Valentin <eduval@amazon.com>
---

From V6 -> V7:
- fixed compile warm when CONFIG_OF=n by wrapping of table into ifdef
- minor changes: kobj_to_dev(), moved BUILD_BUG_ON() to start of function,
and flagged DT table sentinel in a more strict way.
- Also added a MODULE_DEVICE_TABLE() for the of table.

 Documentation/i2c/slave-mqueue-backend.rst | 124 ++++++++++++
 MAINTAINERS                                |   8 +
 drivers/i2c/Kconfig                        |  25 +++
 drivers/i2c/Makefile                       |   1 +
 drivers/i2c/i2c-slave-mqueue.c             | 215 +++++++++++++++++++++
 5 files changed, 373 insertions(+)
 create mode 100644 Documentation/i2c/slave-mqueue-backend.rst
 create mode 100644 drivers/i2c/i2c-slave-mqueue.c

diff --git a/Documentation/i2c/slave-mqueue-backend.rst b/Documentation/i2c/slave-mqueue-backend.rst
new file mode 100644
index 000000000000..376dff998fa3
--- /dev/null
+++ b/Documentation/i2c/slave-mqueue-backend.rst
@@ -0,0 +1,124 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Linux I2C slave message queue backend
+=====================================
+
+:Author: Haiyue Wang <haiyue.wang@linux.intel.com>
+
+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 drivers 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, the below 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
diff --git a/MAINTAINERS b/MAINTAINERS
index a6954776a37e..4bfca09a5f68 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7458,6 +7458,14 @@ L:	linux-i2c@vger.kernel.org
 S:	Maintained
 F:	drivers/i2c/i2c-stub.c
 
+I2C SLAVE MQUEUE DRIVER
+M:	Eduardo Valentin <eduval@amazon.com>
+L:	linux-i2c@vger.kernel.org
+S:	Maintained
+F:	drivers/i2c/i2c-slave-mqueue.c
+F:	Documentation/i2c/slave-mqueue-backend.rst
+F:	Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
+
 I3C SUBSYSTEM
 M:	Boris Brezillon <bbrezillon@kernel.org>
 L:	linux-i3c@lists.infradead.org
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index abedd55a1264..f335924936ae 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -119,6 +119,31 @@ 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.
+
+config I2C_SLAVE_MQUEUE_MESSAGE_SIZE
+	int "The message size of I2C mqueue slave"
+	depends on I2C_SLAVE_MQUEUE
+	default 120
+
+config I2C_SLAVE_MQUEUE_QUEUE_SIZE
+	int "The queue size of I2C mqueue slave"
+	depends on I2C_SLAVE_MQUEUE
+	default 32
+	help
+	  This number MUST be power of 2.
+
 endif
 
 config I2C_DEBUG_CORE
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index bed6ba63c983..9a31bc75a446 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -16,5 +16,6 @@ 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
diff --git a/drivers/i2c/i2c-slave-mqueue.c b/drivers/i2c/i2c-slave-mqueue.c
new file mode 100644
index 000000000000..c17c4911928f
--- /dev/null
+++ b/drivers/i2c/i2c-slave-mqueue.c
@@ -0,0 +1,215 @@
+// 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/device.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+
+#define MQ_MSGBUF_SIZE		CONFIG_I2C_SLAVE_MQUEUE_MESSAGE_SIZE
+#define MQ_QUEUE_SIZE		CONFIG_I2C_SLAVE_MQUEUE_QUEUE_SIZE
+#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 */
+	int			in;
+	int			out;
+
+	struct mq_msg		*curr;
+	int			truncated; /* drop current if truncated */
+	struct mq_msg		queue[MQ_QUEUE_SIZE];
+};
+
+static int i2c_slave_mqueue_callback(struct i2c_client *client,
+				     enum i2c_slave_event event, u8 *val)
+{
+	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");
+			mq->truncated = 1;
+			ret = -EINVAL;
+		}
+		break;
+
+	case I2C_SLAVE_STOP:
+		if (unlikely(mq->truncated || msg->len < 2))
+			break;
+
+		spin_lock(&mq->lock);
+		mq->in = MQ_QUEUE_NEXT(mq->in);
+		mq->curr = &mq->queue[mq->in];
+		mq->curr->len = 0;
+
+		/* 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)
+{
+	struct mq_queue *mq;
+	struct mq_msg *msg;
+	unsigned long flags;
+	bool more = false;
+	ssize_t ret = 0;
+
+	mq = dev_get_drvdata(kobj_to_dev(kobj));
+
+	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;
+
+	BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE));
+
+	mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL);
+	if (!mq)
+		return -ENOMEM;
+
+	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->bin.attr.name);
+	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 },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id i2c_slave_mqueue_of_match[] = {
+	{
+		.compatible = "i2c-slave-mqueue",
+	},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, i2c_slave_mqueue_of_match);
+#endif
+
+static struct i2c_driver i2c_slave_mqueue_driver = {
+	.driver = {
+		.name	= "i2c-slave-mqueue",
+		.of_match_table = of_match_ptr(i2c_slave_mqueue_of_match),
+	},
+	.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 <haiyue.wang@linux.intel.com>");
+MODULE_DESCRIPTION("I2C slave mode for receiving and queuing messages");
-- 
2.21.0

[PATCHv7 3/3] Documentation: ABI: Add i2c-slave-mqueue sysfs documentation

[Eduardo Valentin]

Document the slave-mqueue sysfs attribute used by
the i2c-slave-mqueue driver.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-i2c@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <eduval@amazon.com>
---

changes from V6 to V7:
- none

 .../ABI/testing/sysfs-bus-i2c-devices-slave-mqueue     | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-i2c-devices-slave-mqueue

diff --git a/Documentation/ABI/testing/sysfs-bus-i2c-devices-slave-mqueue b/Documentation/ABI/testing/sysfs-bus-i2c-devices-slave-mqueue
new file mode 100644
index 000000000000..28318108ce85
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-i2c-devices-slave-mqueue
@@ -0,0 +1,10 @@
+What:		/sys/bus/i2c/devices/*/slave-mqueue
+Date:		May 2019
+KernelVersion:	5.2
+Contact:	Eduardo Valentin <eduval@amazon.com>
+Description:
+		Reading to this file will return exactly one message,
+		when available, of the i2c-slave-mqueue device attached
+		to that bus. Userspace can also poll on this file to
+		get notified when new messages are available.
+Users:		i2c-slave-mqueue driver
-- 
2.21.0

Re: [PATCHv7 2/3] i2c: slave-mqueue: add a slave backend to receive and queue messages

[Andy Shevchenko]

On Wed, Jun 5, 2019 at 7:48 PM Eduardo Valentin <eduval@amazon.com> wrote:
>
> From: Haiyue Wang <haiyue.wang@linux.intel.com>
>
> 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.
>
> Note: DT interface and a couple of minor fixes here and there
> by Eduardo, so I kept the original authorship here.

FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

though I prefer simple dropping of of_match_ptr(), and by the way,
#include <of.h> is superfluous and may be changed to
mod_devicetable.h.

Leave above to Wolfram to judge.

> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
> Cc: linux-i2c@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
> Signed-off-by: Eduardo Valentin <eduval@amazon.com>
> ---
>
> From V6 -> V7:
> - fixed compile warm when CONFIG_OF=n by wrapping of table into ifdef
> - minor changes: kobj_to_dev(), moved BUILD_BUG_ON() to start of function,
> and flagged DT table sentinel in a more strict way.
> - Also added a MODULE_DEVICE_TABLE() for the of table.
>
>  Documentation/i2c/slave-mqueue-backend.rst | 124 ++++++++++++
>  MAINTAINERS                                |   8 +
>  drivers/i2c/Kconfig                        |  25 +++
>  drivers/i2c/Makefile                       |   1 +
>  drivers/i2c/i2c-slave-mqueue.c             | 215 +++++++++++++++++++++
>  5 files changed, 373 insertions(+)
>  create mode 100644 Documentation/i2c/slave-mqueue-backend.rst
>  create mode 100644 drivers/i2c/i2c-slave-mqueue.c
>
> diff --git a/Documentation/i2c/slave-mqueue-backend.rst b/Documentation/i2c/slave-mqueue-backend.rst
> new file mode 100644
> index 000000000000..376dff998fa3
> --- /dev/null
> +++ b/Documentation/i2c/slave-mqueue-backend.rst
> @@ -0,0 +1,124 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=====================================
> +Linux I2C slave message queue backend
> +=====================================
> +
> +:Author: Haiyue Wang <haiyue.wang@linux.intel.com>
> +
> +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 drivers 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, the below 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
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a6954776a37e..4bfca09a5f68 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7458,6 +7458,14 @@ L:       linux-i2c@vger.kernel.org
>  S:     Maintained
>  F:     drivers/i2c/i2c-stub.c
>
> +I2C SLAVE MQUEUE DRIVER
> +M:     Eduardo Valentin <eduval@amazon.com>
> +L:     linux-i2c@vger.kernel.org
> +S:     Maintained
> +F:     drivers/i2c/i2c-slave-mqueue.c
> +F:     Documentation/i2c/slave-mqueue-backend.rst
> +F:     Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
> +
>  I3C SUBSYSTEM
>  M:     Boris Brezillon <bbrezillon@kernel.org>
>  L:     linux-i3c@lists.infradead.org
> diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
> index abedd55a1264..f335924936ae 100644
> --- a/drivers/i2c/Kconfig
> +++ b/drivers/i2c/Kconfig
> @@ -119,6 +119,31 @@ 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.
> +
> +config I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> +       int "The message size of I2C mqueue slave"
> +       depends on I2C_SLAVE_MQUEUE
> +       default 120
> +
> +config I2C_SLAVE_MQUEUE_QUEUE_SIZE
> +       int "The queue size of I2C mqueue slave"
> +       depends on I2C_SLAVE_MQUEUE
> +       default 32
> +       help
> +         This number MUST be power of 2.
> +
>  endif
>
>  config I2C_DEBUG_CORE
> diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
> index bed6ba63c983..9a31bc75a446 100644
> --- a/drivers/i2c/Makefile
> +++ b/drivers/i2c/Makefile
> @@ -16,5 +16,6 @@ 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
> diff --git a/drivers/i2c/i2c-slave-mqueue.c b/drivers/i2c/i2c-slave-mqueue.c
> new file mode 100644
> index 000000000000..c17c4911928f
> --- /dev/null
> +++ b/drivers/i2c/i2c-slave-mqueue.c
> @@ -0,0 +1,215 @@
> +// 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/device.h>
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/sysfs.h>
> +
> +#define MQ_MSGBUF_SIZE         CONFIG_I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> +#define MQ_QUEUE_SIZE          CONFIG_I2C_SLAVE_MQUEUE_QUEUE_SIZE
> +#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 */
> +       int                     in;
> +       int                     out;
> +
> +       struct mq_msg           *curr;
> +       int                     truncated; /* drop current if truncated */
> +       struct mq_msg           queue[MQ_QUEUE_SIZE];
> +};
> +
> +static int i2c_slave_mqueue_callback(struct i2c_client *client,
> +                                    enum i2c_slave_event event, u8 *val)
> +{
> +       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");
> +                       mq->truncated = 1;
> +                       ret = -EINVAL;
> +               }
> +               break;
> +
> +       case I2C_SLAVE_STOP:
> +               if (unlikely(mq->truncated || msg->len < 2))
> +                       break;
> +
> +               spin_lock(&mq->lock);
> +               mq->in = MQ_QUEUE_NEXT(mq->in);
> +               mq->curr = &mq->queue[mq->in];
> +               mq->curr->len = 0;
> +
> +               /* 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)
> +{
> +       struct mq_queue *mq;
> +       struct mq_msg *msg;
> +       unsigned long flags;
> +       bool more = false;
> +       ssize_t ret = 0;
> +
> +       mq = dev_get_drvdata(kobj_to_dev(kobj));
> +
> +       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;
> +
> +       BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE));
> +
> +       mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL);
> +       if (!mq)
> +               return -ENOMEM;
> +
> +       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->bin.attr.name);
> +       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 },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id i2c_slave_mqueue_of_match[] = {
> +       {
> +               .compatible = "i2c-slave-mqueue",
> +       },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, i2c_slave_mqueue_of_match);
> +#endif
> +
> +static struct i2c_driver i2c_slave_mqueue_driver = {
> +       .driver = {
> +               .name   = "i2c-slave-mqueue",
> +               .of_match_table = of_match_ptr(i2c_slave_mqueue_of_match),
> +       },
> +       .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 <haiyue.wang@linux.intel.com>");
> +MODULE_DESCRIPTION("I2C slave mode for receiving and queuing messages");
> --
> 2.21.0
>


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCHv7 2/3] i2c: slave-mqueue: add a slave backend to receive and queue messages

[Eduardo Valentin]

On Wed, Jun 05, 2019 at 08:02:11PM +0300, Andy Shevchenko wrote:
> On Wed, Jun 5, 2019 at 7:48 PM Eduardo Valentin <eduval@amazon.com> wrote:
> >
> > From: Haiyue Wang <haiyue.wang@linux.intel.com>
> >
> > 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.
> >
> > Note: DT interface and a couple of minor fixes here and there
> > by Eduardo, so I kept the original authorship here.
> 
> FWIW,
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

Great!

> 
> though I prefer simple dropping of of_match_ptr(), and by the way,
> #include <of.h> is superfluous and may be changed to
> mod_devicetable.h.
> 
> Leave above to Wolfram to judge.

Wolfram, any objections on this series?


> 
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: Wolfram Sang <wsa@the-dreams.de>
> > Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
> > Cc: linux-i2c@vger.kernel.org
> > Cc: devicetree@vger.kernel.org
> > Cc: linux-kernel@vger.kernel.org
> > Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
> > Signed-off-by: Eduardo Valentin <eduval@amazon.com>
> > ---
> >
> > From V6 -> V7:
> > - fixed compile warm when CONFIG_OF=n by wrapping of table into ifdef
> > - minor changes: kobj_to_dev(), moved BUILD_BUG_ON() to start of function,
> > and flagged DT table sentinel in a more strict way.
> > - Also added a MODULE_DEVICE_TABLE() for the of table.
> >
> >  Documentation/i2c/slave-mqueue-backend.rst | 124 ++++++++++++
> >  MAINTAINERS                                |   8 +
> >  drivers/i2c/Kconfig                        |  25 +++
> >  drivers/i2c/Makefile                       |   1 +
> >  drivers/i2c/i2c-slave-mqueue.c             | 215 +++++++++++++++++++++
> >  5 files changed, 373 insertions(+)
> >  create mode 100644 Documentation/i2c/slave-mqueue-backend.rst
> >  create mode 100644 drivers/i2c/i2c-slave-mqueue.c
> >
> > diff --git a/Documentation/i2c/slave-mqueue-backend.rst b/Documentation/i2c/slave-mqueue-backend.rst
> > new file mode 100644
> > index 000000000000..376dff998fa3
> > --- /dev/null
> > +++ b/Documentation/i2c/slave-mqueue-backend.rst
> > @@ -0,0 +1,124 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +=====================================
> > +Linux I2C slave message queue backend
> > +=====================================
> > +
> > +:Author: Haiyue Wang <haiyue.wang@linux.intel.com>
> > +
> > +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 drivers 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, the below 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
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index a6954776a37e..4bfca09a5f68 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -7458,6 +7458,14 @@ L:       linux-i2c@vger.kernel.org
> >  S:     Maintained
> >  F:     drivers/i2c/i2c-stub.c
> >
> > +I2C SLAVE MQUEUE DRIVER
> > +M:     Eduardo Valentin <eduval@amazon.com>
> > +L:     linux-i2c@vger.kernel.org
> > +S:     Maintained
> > +F:     drivers/i2c/i2c-slave-mqueue.c
> > +F:     Documentation/i2c/slave-mqueue-backend.rst
> > +F:     Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
> > +
> >  I3C SUBSYSTEM
> >  M:     Boris Brezillon <bbrezillon@kernel.org>
> >  L:     linux-i3c@lists.infradead.org
> > diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
> > index abedd55a1264..f335924936ae 100644
> > --- a/drivers/i2c/Kconfig
> > +++ b/drivers/i2c/Kconfig
> > @@ -119,6 +119,31 @@ 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.
> > +
> > +config I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> > +       int "The message size of I2C mqueue slave"
> > +       depends on I2C_SLAVE_MQUEUE
> > +       default 120
> > +
> > +config I2C_SLAVE_MQUEUE_QUEUE_SIZE
> > +       int "The queue size of I2C mqueue slave"
> > +       depends on I2C_SLAVE_MQUEUE
> > +       default 32
> > +       help
> > +         This number MUST be power of 2.
> > +
> >  endif
> >
> >  config I2C_DEBUG_CORE
> > diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
> > index bed6ba63c983..9a31bc75a446 100644
> > --- a/drivers/i2c/Makefile
> > +++ b/drivers/i2c/Makefile
> > @@ -16,5 +16,6 @@ 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
> > diff --git a/drivers/i2c/i2c-slave-mqueue.c b/drivers/i2c/i2c-slave-mqueue.c
> > new file mode 100644
> > index 000000000000..c17c4911928f
> > --- /dev/null
> > +++ b/drivers/i2c/i2c-slave-mqueue.c
> > @@ -0,0 +1,215 @@
> > +// 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/device.h>
> > +#include <linux/of.h>
> > +#include <linux/slab.h>
> > +#include <linux/spinlock.h>
> > +#include <linux/sysfs.h>
> > +
> > +#define MQ_MSGBUF_SIZE         CONFIG_I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> > +#define MQ_QUEUE_SIZE          CONFIG_I2C_SLAVE_MQUEUE_QUEUE_SIZE
> > +#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 */
> > +       int                     in;
> > +       int                     out;
> > +
> > +       struct mq_msg           *curr;
> > +       int                     truncated; /* drop current if truncated */
> > +       struct mq_msg           queue[MQ_QUEUE_SIZE];
> > +};
> > +
> > +static int i2c_slave_mqueue_callback(struct i2c_client *client,
> > +                                    enum i2c_slave_event event, u8 *val)
> > +{
> > +       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");
> > +                       mq->truncated = 1;
> > +                       ret = -EINVAL;
> > +               }
> > +               break;
> > +
> > +       case I2C_SLAVE_STOP:
> > +               if (unlikely(mq->truncated || msg->len < 2))
> > +                       break;
> > +
> > +               spin_lock(&mq->lock);
> > +               mq->in = MQ_QUEUE_NEXT(mq->in);
> > +               mq->curr = &mq->queue[mq->in];
> > +               mq->curr->len = 0;
> > +
> > +               /* 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)
> > +{
> > +       struct mq_queue *mq;
> > +       struct mq_msg *msg;
> > +       unsigned long flags;
> > +       bool more = false;
> > +       ssize_t ret = 0;
> > +
> > +       mq = dev_get_drvdata(kobj_to_dev(kobj));
> > +
> > +       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;
> > +
> > +       BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE));
> > +
> > +       mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL);
> > +       if (!mq)
> > +               return -ENOMEM;
> > +
> > +       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->bin.attr.name);
> > +       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 },
> > +       { /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
> > +
> > +#ifdef CONFIG_OF
> > +static const struct of_device_id i2c_slave_mqueue_of_match[] = {
> > +       {
> > +               .compatible = "i2c-slave-mqueue",
> > +       },
> > +       { /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(of, i2c_slave_mqueue_of_match);
> > +#endif
> > +
> > +static struct i2c_driver i2c_slave_mqueue_driver = {
> > +       .driver = {
> > +               .name   = "i2c-slave-mqueue",
> > +               .of_match_table = of_match_ptr(i2c_slave_mqueue_of_match),
> > +       },
> > +       .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 <haiyue.wang@linux.intel.com>");
> > +MODULE_DESCRIPTION("I2C slave mode for receiving and queuing messages");
> > --
> > 2.21.0
> >
> 
> 
> -- 
> With Best Regards,
> Andy Shevchenko

-- 
All the best,
Eduardo Valentin

Re: [PATCHv7 1/3] dt-bindings: i2c: document bindings for i2c-slave-mqueue

[Rob Herring]

On Wed, Jun 05, 2019 at 09:46:49AM -0700, Eduardo Valentin wrote:
> Document the i2c-slave-mqueue binding by adding
> descriptor, required properties, and example.
> 
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: linux-i2c@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Eduardo Valentin <eduval@amazon.com>
> ---
> 
> Changes from V6 to V7:
> - none
> 
>  .../bindings/i2c/i2c-slave-mqueue.txt         | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt b/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
> new file mode 100644
> index 000000000000..eb1881a4fc0e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
> @@ -0,0 +1,34 @@
> +===============================================
> +Device Tree for I2C slave message queue backend
> +===============================================
> +
> +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.

So the address 0x10 in the example below is the address of the I2C 
controller?

> +
> +This I2C slave mqueue (message queue) 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.
> +
> +Links
> +----
> +`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>`_
> +
> +Required Properties:
> +- compatible		: should be "i2c-slave-mqueue"

There is no mention of mqueue (or queue) in these specs. Where does that 
come from? Perhaps something more closely matching the protocol would be 
better name.

> +- reg			: slave address
> +
> +Example:
> +
> +i2c {

Would there be other slaves? 

The common binding states 'multi-master' property should be present. 

I need a more complete example.

> +	slave_mqueue: i2c-slave-mqueue {
> +		compatible = "i2c-slave-mqueue";
> +		reg = <0x10>;
> +	};
> +};
> -- 
> 2.21.0
> 

Re: [PATCHv7 1/3] dt-bindings: i2c: document bindings for i2c-slave-mqueue

[Wang, Haiyue]

在 2019-06-12 07:14, Rob Herring 写道:
> On Wed, Jun 05, 2019 at 09:46:49AM -0700, Eduardo Valentin wrote:
>> Document the i2c-slave-mqueue binding by adding
>> descriptor, required properties, and example.
>>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Wolfram Sang <wsa@the-dreams.de>
>> Cc: linux-i2c@vger.kernel.org
>> Cc: devicetree@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Eduardo Valentin <eduval@amazon.com>
>> ---
>>
>> Changes from V6 to V7:
>> - none
>>
>>   .../bindings/i2c/i2c-slave-mqueue.txt         | 34 +++++++++++++++++++
>>   1 file changed, 34 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
>>
>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt b/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
>> new file mode 100644
>> index 000000000000..eb1881a4fc0e
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/i2c/i2c-slave-mqueue.txt
>> @@ -0,0 +1,34 @@
>> +===============================================
>> +Device Tree for I2C slave message queue backend
>> +===============================================
>> +
>> +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.
> So the address 0x10 in the example below is the address of the I2C
> controller?
>
>> +
>> +This I2C slave mqueue (message queue) is used to receive and queue
Hi Rob, This is mqueue comes from, not from specs directly.
>> +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.
>> +
>> +Links
>> +----
>> +`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>`_
>> +
>> +Required Properties:
>> +- compatible		: should be "i2c-slave-mqueue"
> There is no mention of mqueue (or queue) in these specs. Where does that
> come from? Perhaps something more closely matching the protocol would be
> better name.
>
>> +- reg			: slave address
>> +
>> +Example:
>> +
>> +i2c {
> Would there be other slaves?
>
> The common binding states 'multi-master' property should be present.
>
> I need a more complete example.
>
>> +	slave_mqueue: i2c-slave-mqueue {
>> +		compatible = "i2c-slave-mqueue";
>> +		reg = <0x10>;

Hi Eduardo,

Looks like the slave reg missed the key value bit:


https://elinux.org/images/f/f6/ELCE15-WolframSang-ShinyNewI2CSlaveFramework.pdf

Example: reg = <(I2C_OWN_SLAVE_ADDRESS | 0x42)>;


>> +	};
>> +};
>> -- 
>> 2.21.0
>>

Re: [PATCHv7 1/3] dt-bindings: i2c: document bindings for i2c-slave-mqueue

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 213 bytes --]


> Looks like the slave reg missed the key value bit:
> 
> 
> https://elinux.org/images/f/f6/ELCE15-WolframSang-ShinyNewI2CSlaveFramework.pdf
> 
> Example: reg = <(I2C_OWN_SLAVE_ADDRESS | 0x42)>;

Yes.


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCHv7 1/3] dt-bindings: i2c: document bindings for i2c-slave-mqueue

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 1727 bytes --]

> > +===============================================
> > +Device Tree for I2C slave message queue backend
> > +===============================================
> > +
> > +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.
> 
> So the address 0x10 in the example below is the address of the I2C 
> controller?

Yes.

> > +This I2C slave mqueue (message queue) 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.
> > +
> > +Links
> > +----
> > +`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>`_
> > +
> > +Required Properties:
> > +- compatible		: should be "i2c-slave-mqueue"
> 
> There is no mention of mqueue (or queue) in these specs. Where does that 
> come from? Perhaps something more closely matching the protocol would be 
> better name.
> 
> > +- reg			: slave address
> > +
> > +Example:
> > +
> > +i2c {
> 
> Would there be other slaves? 
> 
> The common binding states 'multi-master' property should be present. 
> 
> I need a more complete example.

Ack. Either that or a bit more explanation, e.g. if sending
packets is planned from userspace?


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCHv7 2/3] i2c: slave-mqueue: add a slave backend to receive and queue messages

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 2607 bytes --]

Hi Eduardo,

thanks for stepping up and pushing this further!

On Wed, Jun 05, 2019 at 09:46:50AM -0700, Eduardo Valentin wrote:
> From: Haiyue Wang <haiyue.wang@linux.intel.com>
> 
> 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.

So, this is a read-only bin file. Sending is done via the standard
i2c-dev driver? Or not needed at all?

Regarding, IPMB, how does this related to the recently merged IPMB slave
driver?

http://patchwork.ozlabs.org/patch/1113278/

> 
> Note: DT interface and a couple of minor fixes here and there
> by Eduardo, so I kept the original authorship here.
> 
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
> Cc: linux-i2c@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
> Signed-off-by: Eduardo Valentin <eduval@amazon.com>

> +I2C SLAVE MQUEUE DRIVER
> +M:	Eduardo Valentin <eduval@amazon.com>

Cool, thanks!

> +config I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> +	int "The message size of I2C mqueue slave"
> +	depends on I2C_SLAVE_MQUEUE
> +	default 120
> +
> +config I2C_SLAVE_MQUEUE_QUEUE_SIZE
> +	int "The queue size of I2C mqueue slave"
> +	depends on I2C_SLAVE_MQUEUE
> +	default 32
> +	help
> +	  This number MUST be power of 2.

I am not happy with this being a Kconfig option. Best would be a
per-instance configuration, so we could have differently sized mqueues
at runtime. I could think of another sysfs-file like
"mqueue-slave-config" which would appear after writing to 'new_device'.
And only after writing to 'mqueue-slave-config', the bin file to read
from would show up. But it is just a quick brainstorming, maybe you have
a better idea?

> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2017 - 2018, Intel Corporation.

A short description what this driver does would be nice.

Rest looks decent from a glimpse. I haven't looked into the gory details
yet, though, because I want to get the high level things straight first.

Kind regards,

   Wolfram


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]