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Date:   Wed, 5 Jun 2019 10:28:06 -0700
From:   Eduardo Valentin <eduval@...zon.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Wolfram Sang <wsa@...-dreams.de>
CC:     Eduardo Valentin <eduval@...zon.com>,
        Haiyue Wang <haiyue.wang@...ux.intel.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Andriy Shevchenko <andriy.shevchenko@...el.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv7 2/3] i2c: slave-mqueue: add a slave backend to receive
 and queue messages

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@...zon.com> wrote:
> >
> > From: Haiyue Wang <haiyue.wang@...ux.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@...il.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@...nel.org>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Wolfram Sang <wsa@...-dreams.de>
> > Cc: Andy Shevchenko <andriy.shevchenko@...el.com>
> > Cc: linux-i2c@...r.kernel.org
> > Cc: devicetree@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: Haiyue Wang <haiyue.wang@...ux.intel.com>
> > Signed-off-by: Eduardo Valentin <eduval@...zon.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@...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 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@...r.kernel.org
> >  S:     Maintained
> >  F:     drivers/i2c/i2c-stub.c
> >
> > +I2C SLAVE MQUEUE DRIVER
> > +M:     Eduardo Valentin <eduval@...zon.com>
> > +L:     linux-i2c@...r.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@...nel.org>
> >  L:     linux-i3c@...ts.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@...ux.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

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