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Subject: Re: [PATCH v2] platform/chrome: cros_ec_chardev: Add a poll handler
 to receive MKBP events
To:     Gwendal Grignou <gwendal@chromium.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Collabora Kernel ML <kernel@collabora.com>,
        Vincent Palatin <vpalatin@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Benson Leung <bleung@chromium.org>,
        Lee Jones <lee.jones@linaro.org>
References: <20190902160848.4738-1-enric.balletbo@collabora.com>
 <20190902162420.GU2680@smile.fi.intel.com>
 <CAPUE2utLqOGhPXFO1w8Fhu_use7nbu+Q+A+jL5vL_9ROJjnQKQ@mail.gmail.com>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <10c30679-6542-2a35-0d68-bb569881dc26@collabora.com>
Date:   Thu, 19 Sep 2019 15:05:38 +0200
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Hi,

On 5/9/19 23:25, Gwendal Grignou wrote:
> On Mon, Sep 2, 2019 at 9:24 AM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
>>
>> On Mon, Sep 02, 2019 at 06:08:48PM +0200, Enric Balletbo i Serra wrote:
>>> Allow to poll on the cros_ec device to receive the MKBP events.
>>>
>>> The /dev/cros_[ec|fp|..] file operations now implements the poll
>>> operation. The userspace can now receive specific MKBP events by doing
>>> the
>>> following:
>>> - Open the /dev/cros_XX file.
>>> - Call the CROS_EC_DEV_IOCEVENTMASK ioctl with the bitmap of the MKBP
>>>   events it wishes to receive as argument.
>>> - Poll on the file descriptor.
>>> - When it gets POLLIN, do a read on the file descriptor, the first
>>>   queued event will be returned (using the struct
>>>   ec_response_get_next_event format: one byte of event type, then
>>>   the payload).
>>>
>>> The read() operation returns at most one event even if there are several
>>> queued, and it might be truncated if the buffer is smaller than the
>>> event (but the caller should know the maximum size of the events it is
>>> reading).
>>>
>>> read() used to return the EC version string, it still does it when no
>>> event mask or an empty event is set for backward compatibility (despite
>>> nobody really using this feature).
>>>
>>> This will be used, for example, by the userspace daemon to receive and
>>> treat the EC_MKBP_EVENT_FINGERPRINT sent by the FP MCU.
>>>
>>
>> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Reviewed-by: Gwendal Grignou <gwendal@chromium.org>

I modified the patch with Gwendal nits and applied for 5.4, the patches went to
linux-next some time ago, so sorry for late notice.

Thanks,
 Enric


>>
>>> Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
>>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
>>> ---
>>> Note that this patch depends on the immutable branch [1] to apply
>>> cleanly.
>>>
>>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git/log/?h=ib-mfd-extcon-hid-i2c-iio-input-media-chrome-power-pwm-rtc-sound-5.4
>>>
>>>
>>> Changes in v2:
>>> - Moved the code to the cros_ec_chardev driver.
>>>
>>>  drivers/platform/chrome/cros_ec_chardev.c     | 177 +++++++++++++++++-
>>>  include/linux/platform_data/cros_ec_chardev.h |   1 +
>>>  2 files changed, 173 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c
>>> index 08abd7e5c7bf..eabb1fe85688 100644
>>> --- a/drivers/platform/chrome/cros_ec_chardev.c
>>> +++ b/drivers/platform/chrome/cros_ec_chardev.c
>>> @@ -16,21 +16,42 @@
>>>  #include <linux/mfd/cros_ec.h>
>>>  #include <linux/miscdevice.h>
>>>  #include <linux/module.h>
>>> +#include <linux/notifier.h>
>>>  #include <linux/platform_data/cros_ec_chardev.h>
>>>  #include <linux/platform_data/cros_ec_commands.h>
>>>  #include <linux/platform_data/cros_ec_proto.h>
>>>  #include <linux/platform_device.h>
>>> +#include <linux/poll.h>
>>>  #include <linux/slab.h>
>>>  #include <linux/types.h>
>>>  #include <linux/uaccess.h>
>>>
>>>  #define DRV_NAME             "cros-ec-chardev"
>>>
>>> +/* Arbitrary bounded size for the event queue */
>>> +#define CROS_MAX_EVENT_LEN   PAGE_SIZE
>>> +
>>>  struct chardev_data {
>>>       struct cros_ec_dev *ec_dev;
>>>       struct miscdevice misc;
>>>  };
>>>
>>> +struct chardev_priv {
>>> +     struct cros_ec_dev *ec_dev;
>>> +     struct notifier_block notifier;
>>> +     wait_queue_head_t wait_event;
>>> +     unsigned long event_mask;
>>> +     struct list_head events;
>>> +     size_t event_len;
>>> +};
>>> +
>>> +struct ec_event {
>>> +     struct list_head node;
>>> +     size_t size;
>>> +     u8 event_type;
>>> +     u8 data[0];
>>> +};
>>> +
>>>  static int ec_get_version(struct cros_ec_dev *ec, char *str, int maxlen)
>>>  {
>>>       static const char * const current_image_name[] = {
>>> @@ -69,6 +90,71 @@ static int ec_get_version(struct cros_ec_dev *ec, char *str, int maxlen)
>>>       return ret;
>>>  }
>>>
>>> +static int ec_mkbp_event(struct notifier_block *nb,
>>> +                      unsigned long queued_during_suspend,
>>> +                      void *_notify)
> nit: call it cros_ec_chardev_mkbp_event()  to fit other functions
> naming convention. Change only if a v3 is needed.
>>> +{
>>> +     struct chardev_priv *priv = container_of(nb, struct chardev_priv,
>>> +                                              notifier);
>>> +     struct cros_ec_device *ec_dev = priv->ec_dev->ec_dev;
>>> +     struct ec_event *event;
>>> +     unsigned long event_bit = 1 << ec_dev->event_data.event_type;
>>> +     int total_size = sizeof(*event) + ec_dev->event_size;
>>> +
>>> +     if (!(event_bit & priv->event_mask) ||
>>> +         (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
>>> +             return NOTIFY_DONE;
>>> +
>>> +     event = kzalloc(total_size, GFP_KERNEL);
>>> +     if (!event)
>>> +             return NOTIFY_DONE;
>>> +
>>> +     event->size = ec_dev->event_size;
>>> +     event->event_type = ec_dev->event_data.event_type;
>>> +     memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
>>> +
>>> +     spin_lock(&priv->wait_event.lock);
>>> +     list_add_tail(&event->node, &priv->events);
>>> +     priv->event_len += total_size;
>>> +     wake_up_locked(&priv->wait_event);
>>> +     spin_unlock(&priv->wait_event.lock);
>>> +
>>> +     return NOTIFY_OK;
>>> +}
>>> +
>>> +static struct ec_event *ec_fetch_event(struct chardev_priv *priv, bool fetch,
>>> +                                    bool block)
> nit: cros_ec_chardev_fetch_event()
>>> +{
>>> +     struct ec_event *event;
>>> +     int err;
>>> +
>>> +     spin_lock(&priv->wait_event.lock);
>>> +     if (!block && list_empty(&priv->events)) {
>>> +             event = ERR_PTR(-EWOULDBLOCK);
>>> +             goto out;
>>> +     }
>>> +
>>> +     if (!fetch) {
>>> +             event = NULL;
>>> +             goto out;
>>> +     }
>>> +
>>> +     err = wait_event_interruptible_locked(priv->wait_event,
>>> +                                           !list_empty(&priv->events));
>>> +     if (err) {
>>> +             event = ERR_PTR(err);
>>> +             goto out;
>>> +     }
>>> +
>>> +     event = list_first_entry(&priv->events, struct ec_event, node);
>>> +     list_del(&event->node);
>>> +     priv->event_len -= sizeof(*event) + event->size;
>>> +
>>> +out:
>>> +     spin_unlock(&priv->wait_event.lock);
>>> +     return event;
>>> +}
>>> +
>>>  /*
>>>   * Device file ops
>>>   */
>>> @@ -76,11 +162,40 @@ static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
>>>  {
>>>       struct miscdevice *mdev = filp->private_data;
>>>       struct cros_ec_dev *ec_dev = dev_get_drvdata(mdev->parent);
>>> +     struct chardev_priv *priv;
>>> +     int ret;
>>> +
>>> +     priv = kzalloc(sizeof(*priv), GFP_KERNEL);
>>> +     if (!priv)
>>> +             return -ENOMEM;
>>>
>>> -     filp->private_data = ec_dev;
>>> +     priv->ec_dev = ec_dev;
>>> +     filp->private_data = priv;
>>> +     INIT_LIST_HEAD(&priv->events);
>>> +     init_waitqueue_head(&priv->wait_event);
>>>       nonseekable_open(inode, filp);
>>>
>>> -     return 0;
>>> +     priv->notifier.notifier_call = ec_mkbp_event;
>>> +     ret = blocking_notifier_chain_register(&ec_dev->ec_dev->event_notifier,
>>> +                                            &priv->notifier);
>>> +     if (ret) {
>>> +             dev_err(ec_dev->dev, "failed to register event notifier\n");
>>> +             kfree(priv);
>>> +     }
>>> +
>>> +     return ret;
>>> +}
>>> +
>>> +static __poll_t cros_ec_chardev_poll(struct file *filp, poll_table *wait)
>>> +{
>>> +     struct chardev_priv *priv = filp->private_data;
>>> +
>>> +     poll_wait(filp, &priv->wait_event, wait);
>>> +
>>> +     if (list_empty(&priv->events))
>>> +             return 0;
>>> +
>>> +     return EPOLLIN | EPOLLRDNORM;
>>>  }
>>>
>>>  static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
>>> @@ -88,14 +203,42 @@ static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
>>>  {
>>>       char msg[sizeof(struct ec_response_get_version) +
>>>                sizeof(CROS_EC_DEV_VERSION)];
>>> -     struct cros_ec_dev *ec = filp->private_data;
>>> +     struct chardev_priv *priv = filp->private_data;
>>> +     struct cros_ec_dev *ec_dev = priv->ec_dev;
>>>       size_t count;
>>>       int ret;
>>>
>>> +     if (priv->event_mask) { /* queued MKBP event */
>>> +             struct ec_event *event;
>>> +
>>> +             event = ec_fetch_event(priv, length != 0,
>>> +                                    !(filp->f_flags & O_NONBLOCK));
>>> +             if (IS_ERR(event))
>>> +                     return PTR_ERR(event);
>>> +             /*
>>> +              * length == 0 is special - no IO is done but we check
>>> +              * for error conditions.
>>> +              */
>>> +             if (length == 0)
>>> +                     return 0;
>>> +
>>> +             /* The event is 1 byte of type plus the payload */
>>> +             count = min(length, event->size + 1);
>>> +             ret = copy_to_user(buffer, &event->event_type, count);
>>> +             kfree(event);
>>> +             if (ret) /* the copy failed */
>>> +                     return -EFAULT;
>>> +             *offset = count;
>>> +             return count;
>>> +     }
>>> +
>>> +     /*
>>> +      * Legacy behavior if no event mask is defined
>>> +      */
>>>       if (*offset != 0)
>>>               return 0;
>>>
>>> -     ret = ec_get_version(ec, msg, sizeof(msg));
>>> +     ret = ec_get_version(ec_dev, msg, sizeof(msg));
>>>       if (ret)
>>>               return ret;
>>>
>>> @@ -108,6 +251,24 @@ static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
>>>       return count;
>>>  }
>>>
>>> +static int cros_ec_chardev_release(struct inode *inode, struct file *filp)
>>> +{
>>> +     struct chardev_priv *priv = filp->private_data;
>>> +     struct cros_ec_dev *ec_dev = priv->ec_dev;
>>> +     struct ec_event *event, *e;
>>> +
>>> +     blocking_notifier_chain_unregister(&ec_dev->ec_dev->event_notifier,
>>> +                                        &priv->notifier);
>>> +
>>> +     list_for_each_entry_safe(event, e, &priv->events, node) {
>>> +             list_del(&event->node);
>>> +             kfree(event);
>>> +     }
>>> +     kfree(priv);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>>  /*
>>>   * Ioctls
>>>   */
>>> @@ -181,7 +342,8 @@ static long cros_ec_chardev_ioctl_readmem(struct cros_ec_dev *ec,
>>>  static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
>>>                                  unsigned long arg)
>>>  {
>>> -     struct cros_ec_dev *ec = filp->private_data;
>>> +     struct chardev_priv *priv = filp->private_data;
>>> +     struct cros_ec_dev *ec = priv->ec_dev;
>>>
>>>       if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
>>>               return -ENOTTY;
>>> @@ -191,6 +353,9 @@ static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
>>>               return cros_ec_chardev_ioctl_xcmd(ec, (void __user *)arg);
>>>       case CROS_EC_DEV_IOCRDMEM:
>>>               return cros_ec_chardev_ioctl_readmem(ec, (void __user *)arg);
>>> +     case CROS_EC_DEV_IOCEVENTMASK:
>>> +             priv->event_mask = arg;
>>> +             return 0;
>>>       }
>>>
>>>       return -ENOTTY;
>>> @@ -198,7 +363,9 @@ static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
>>>
>>>  static const struct file_operations chardev_fops = {
>>>       .open           = cros_ec_chardev_open,
>>> +     .poll           = cros_ec_chardev_poll,
>>>       .read           = cros_ec_chardev_read,
>>> +     .release        = cros_ec_chardev_release,
>>>       .unlocked_ioctl = cros_ec_chardev_ioctl,
>>>  #ifdef CONFIG_COMPAT
>>>       .compat_ioctl   = cros_ec_chardev_ioctl,
>>> diff --git a/include/linux/platform_data/cros_ec_chardev.h b/include/linux/platform_data/cros_ec_chardev.h
>>> index 973b2615aa02..7de8faaf77df 100644
>>> --- a/include/linux/platform_data/cros_ec_chardev.h
>>> +++ b/include/linux/platform_data/cros_ec_chardev.h
>>> @@ -33,5 +33,6 @@ struct cros_ec_readmem {
>>>  #define CROS_EC_DEV_IOC       0xEC
>>>  #define CROS_EC_DEV_IOCXCMD   _IOWR(CROS_EC_DEV_IOC, 0, struct cros_ec_command)
>>>  #define CROS_EC_DEV_IOCRDMEM  _IOWR(CROS_EC_DEV_IOC, 1, struct cros_ec_readmem)
>>> +#define CROS_EC_DEV_IOCEVENTMASK _IO(CROS_EC_DEV_IOC, 2)
>>>
>>>  #endif /* _CROS_EC_DEV_H_ */
>>> --
>>> 2.20.1
>>>
>>
>> --
>> With Best Regards,
>> Andy Shevchenko
>>
>>
>