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Date:   Thu, 30 May 2019 10:11:12 -0700
From:   Eduardo Valentin <eduval@...zon.com>
To:     Eduardo Valentin <eduval@...zon.com>
CC:     Haiyue Wang <haiyue.wang@...ux.intel.com>, <wsa@...-dreams.de>,
        <brendanhiggins@...gle.com>, <linux-i2c@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <openbmc@...ts.ozlabs.org>,
        <jarkko.nikula@...ux.intel.com>, <andriy.shevchenko@...el.com>,
        <jae.hyun.yoo@...ux.intel.com>
Subject: Re: [PATCH i2c/slave-mqueue v5] i2c: slave-mqueue: add a slave
 backend to receive and queue messages

On Wed, May 29, 2019 at 08:46:48PM -0700, Eduardo Valentin wrote:
> On Tue, Apr 24, 2018 at 01:06:32AM +0800, Haiyue Wang wrote:
> > 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 <haiyue.wang@...ux.intel.com>
> > ---
> > v4 -> v5:
> >  - Typo: bellowing -> the below
> > 
> > v3 -> v4:
> >  - Drop the small message after receiving I2C STOP.
> > 
> > v2 -> v3:
> >  - Just remove the ';' after the end '}' of i2c_slave_mqueue_probe().
> > 
> > v1 -> v2:
> >  - Change MQ_MSGBUF_SIZE and MQ_QUEUE_SIZE to be configurable by Kconfig.
> > ---
> >  Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++
> >  drivers/i2c/Kconfig                        |  25 ++++
> >  drivers/i2c/Makefile                       |   1 +
> >  drivers/i2c/i2c-slave-mqueue.c             | 203 +++++++++++++++++++++++++++++
> >  4 files changed, 354 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 0000000..3966cf0
> > --- /dev/null
> > +++ b/Documentation/i2c/slave-mqueue-backend.rst
> > @@ -0,0 +1,125 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +=====================================
> > +Linux I2C slave message queue backend
> > +=====================================
> > +
> > +:Author: Haiyue Wang <haiyue.wang@...ux.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 dirvers under slave mode.
> 
> s/dirvers/drivers/g
> 
> > +
> > +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/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
> > index efc3354..31e57d2 100644
> > --- a/drivers/i2c/Kconfig
> > +++ b/drivers/i2c/Kconfig
> > @@ -118,6 +118,31 @@ if I2C_SLAVE
> >  config I2C_SLAVE_EEPROM
> >  	tristate "I2C eeprom slave driver"
> >  
> > +config I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> > +	int "The message size of I2C mqueue slave"
> > +	default 120
> 
> Can you please add a help entry here?
> 
> > +
> > +config I2C_SLAVE_MQUEUE_QUEUE_SIZE
> > +	int "The queue size of I2C mqueue slave"
> > +	default 32
> > +	help
> > +	  This number MUST be power of 2.
> > +
> 
> Shouldnt the two above depend on I2C_SLAVE_MQUEUE?
> 
> 
> > +config I2C_SLAVE_MQUEUE
> > +	tristate "I2C mqueue (message queue) slave driver"
> > +	select I2C_SLAVE_MQUEUE_MESSAGE_SIZE
> > +	select I2C_SLAVE_MQUEUE_QUEUE_SIZE

I actually get the following Warning when compiling this:
drivers/i2c/Kconfig:123:warning: 'I2C_SLAVE_MQUEUE_MESSAGE_SIZE' has wrong type. 'select' only accept arguments of bool and tristate type

So, yes, you should remove the selects above, and make the two configs depend on this one. something like:

--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -118,20 +118,8 @@ if I2C_SLAVE
 config I2C_SLAVE_EEPROM
        tristate "I2C eeprom slave driver"
 
-config I2C_SLAVE_MQUEUE_MESSAGE_SIZE
-       int "The message size of I2C mqueue slave"
-       default 120
-
-config I2C_SLAVE_MQUEUE_QUEUE_SIZE
-       int "The queue size of I2C mqueue slave"
-       default 32
-       help
-         This number MUST be power of 2.
-
 config I2C_SLAVE_MQUEUE
        tristate "I2C mqueue (message queue) slave driver"
-       select I2C_SLAVE_MQUEUE_MESSAGE_SIZE
-       select I2C_SLAVE_MQUEUE_QUEUE_SIZE
        help
          Some protocols over I2C are designed for bi-directional transferring
          messages by using I2C Master Write protocol. This driver is used to
@@ -143,6 +131,18 @@ config I2C_SLAVE_MQUEUE
          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



And obviously, add a proper help entry for the *SIZE entries.
> > +	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
> > diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
> > index 72c94c6..7ec287b 100644
> > --- a/drivers/i2c/Makefile
> > +++ b/drivers/i2c/Makefile
> > @@ -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
> > diff --git a/drivers/i2c/i2c-slave-mqueue.c b/drivers/i2c/i2c-slave-mqueue.c
> > new file mode 100644
> > index 0000000..424f435
> > --- /dev/null
> > +++ b/drivers/i2c/i2c-slave-mqueue.c
> > @@ -0,0 +1,203 @@
> > +// 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		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(container_of(kobj, struct device, 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;
> > +
> > +	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->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 },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
> 
> Also, can we have device tree support for this driver?
> 
> > +
> > +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 <haiyue.wang@...ux.intel.com>");
> > +MODULE_DESCRIPTION("I2C slave mode for receiving and queuing messages");
> > -- 
> > 2.7.4
> > 
> 
> -- 
> All the best,
> Eduardo Valentin

-- 
All the best,
Eduardo Valentin

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