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Date: Mon, 2 Sep 2019 19:24:20 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc: linux-kernel@...r.kernel.org,
Collabora Kernel ML <kernel@...labora.com>,
Vincent Palatin <vpalatin@...omium.org>,
Gwendal Grignou <gwendal@...omium.org>,
Guenter Roeck <groeck@...omium.org>,
Thomas Gleixner <tglx@...utronix.de>,
Benson Leung <bleung@...omium.org>,
Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH v2] platform/chrome: cros_ec_chardev: Add a poll handler
to receive MKBP events
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@...ux.intel.com>
> Signed-off-by: Vincent Palatin <vpalatin@...omium.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.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)
> +{
> + 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)
> +{
> + 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
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