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Message-ID: <20250422203753.GM17813@pendragon.ideasonboard.com>
Date: Tue, 22 Apr 2025 23:37:53 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Hans de Goede <hdegoede@...hat.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Guennadi Liakhovetski <guennadi.liakhovetski@...el.com>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Subject: Re: [PATCH v6 3/5] media: uvcvideo: Increase/decrease the PM counter
per IOCTL
Hi Ricardo,
Thank you for the patch.
On Thu, Mar 27, 2025 at 09:05:29PM +0000, Ricardo Ribalda wrote:
> Now we call uvc_pm_get/put from the device open/close. This low
> level of granularity might leave the camera powered on in situations
> where it is not needed.
>
> Increase the granularity by increasing and decreasing the Power
> Management counter per ioctl. There are two special cases where the
> power management outlives the ioctl: async controls and streamon. Handle
> those cases as well.
>
> In a future patch, we will remove the uvc_pm_get/put from open/close.
>
> Reviewed-by: Hans de Goede <hdegoede@...hat.com>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
> drivers/media/usb/uvc/uvc_ctrl.c | 37 +++++++++++++++++++++++++++----------
> drivers/media/usb/uvc/uvc_v4l2.c | 39 +++++++++++++++++++++++++++++++++++++--
> 2 files changed, 64 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index cbf19aa1d82374a08cf79b6a6787fa348b83523a..3fad289e41fd5a757f8dcf30a6238c694fc4250c 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1812,38 +1812,49 @@ static void uvc_ctrl_send_slave_event(struct uvc_video_chain *chain,
> uvc_ctrl_send_event(chain, handle, ctrl, mapping, val, changes);
> }
>
> -static void uvc_ctrl_set_handle(struct uvc_fh *handle, struct uvc_control *ctrl,
> - struct uvc_fh *new_handle)
> +static int uvc_ctrl_set_handle(struct uvc_fh *handle, struct uvc_control *ctrl,
> + struct uvc_fh *new_handle)
> {
> lockdep_assert_held(&handle->chain->ctrl_mutex);
>
> if (new_handle) {
> + int ret;
> +
> if (ctrl->handle)
> dev_warn_ratelimited(&handle->stream->dev->udev->dev,
> "UVC non compliance: Setting an async control with a pending operation.");
>
> if (new_handle == ctrl->handle)
> - return;
> + return 0;
>
> if (ctrl->handle) {
> WARN_ON(!ctrl->handle->pending_async_ctrls);
> if (ctrl->handle->pending_async_ctrls)
> ctrl->handle->pending_async_ctrls--;
> + ctrl->handle = new_handle;
> + handle->pending_async_ctrls++;
As commented previously, your usage of the handle variable is confusing.
ctrl->handle->pending_async_ctrls++;
> + return 0;
> }
>
> + ret = uvc_pm_get(handle->chain->dev);
> + if (ret)
> + return ret;
> +
> ctrl->handle = new_handle;
> handle->pending_async_ctrls++;
ctrl->handle->pending_async_ctrls++;
> - return;
> + return 0;
> }
>
> /* Cannot clear the handle for a control not owned by us.*/
> if (WARN_ON(ctrl->handle != handle))
> - return;
> + return -EINVAL;
>
> ctrl->handle = NULL;
> if (WARN_ON(!handle->pending_async_ctrls))
> - return;
> + return -EINVAL;
> handle->pending_async_ctrls--;
> + uvc_pm_put(handle->chain->dev);
> + return 0;
> }
>
> void uvc_ctrl_status_event(struct uvc_video_chain *chain,
> @@ -2137,15 +2148,16 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
>
> ctrl->dirty = 0;
>
> + if (!rollback && handle && !ret &&
> + ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
> + ret = uvc_ctrl_set_handle(handle, ctrl, handle);
> +
> if (ret < 0) {
> if (err_ctrl)
> *err_ctrl = ctrl;
> return ret;
> }
>
> - if (!rollback && handle &&
> - ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
> - uvc_ctrl_set_handle(handle, ctrl, handle);
> }
>
> return 0;
> @@ -3222,6 +3234,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> {
> struct uvc_entity *entity;
> + int i;
>
> guard(mutex)(&handle->chain->ctrl_mutex);
>
> @@ -3236,7 +3249,11 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> }
> }
>
> - WARN_ON(handle->pending_async_ctrls);
> + if (!WARN_ON(handle->pending_async_ctrls))
> + return;
> +
> + for (i = 0; i < handle->pending_async_ctrls; i++)
> + uvc_pm_put(handle->stream->dev);
> }
>
> /*
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 1d5be045d04ecbf17e65e14b390e494a294b735f..8bccf7e17528b62f2594c0dad99405034532973d 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -697,6 +697,9 @@ static int uvc_v4l2_release(struct file *file)
> if (uvc_has_privileges(handle))
> uvc_queue_release(&stream->queue);
>
> + if (handle->is_streaming)
> + uvc_pm_put(stream->dev);
> +
> /* Release the file handle. */
> uvc_dismiss_privileges(handle);
> v4l2_fh_del(&handle->vfh);
> @@ -862,6 +865,11 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
> if (ret)
> return ret;
>
> + ret = uvc_pm_get(stream->dev);
Shouldn't this be done before calling uvc_queue_streamon() ? There's
another PM reference being held by the ioctl handler, but if the code is
refactored later, it would be good to make sure we resume the device
before starting streaming.
> + if (ret) {
> + uvc_queue_streamoff(&stream->queue, type);
> + return ret;
> + }
> handle->is_streaming = true;
>
> return 0;
> @@ -879,7 +887,10 @@ static int uvc_ioctl_streamoff(struct file *file, void *fh,
> guard(mutex)(&stream->mutex);
>
> uvc_queue_streamoff(&stream->queue, type);
> - handle->is_streaming = false;
> + if (handle->is_streaming) {
> + handle->is_streaming = false;
> + uvc_pm_put(stream->dev);
> + }
>
> return 0;
> }
> @@ -1378,9 +1389,11 @@ static int uvc_v4l2_put_xu_query(const struct uvc_xu_control_query *kp,
> #define UVCIOC_CTRL_MAP32 _IOWR('u', 0x20, struct uvc_xu_control_mapping32)
> #define UVCIOC_CTRL_QUERY32 _IOWR('u', 0x21, struct uvc_xu_control_query32)
>
> +DEFINE_FREE(uvc_pm_put, struct uvc_device *, if (_T) uvc_pm_put(_T))
> static long uvc_v4l2_compat_ioctl32(struct file *file,
> unsigned int cmd, unsigned long arg)
> {
> + struct uvc_device *uvc_device __free(uvc_pm_put) = NULL;
> struct uvc_fh *handle = file->private_data;
> union {
> struct uvc_xu_control_mapping xmap;
> @@ -1389,6 +1402,12 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
> void __user *up = compat_ptr(arg);
> long ret;
>
> + ret = uvc_pm_get(handle->stream->dev);
> + if (ret)
> + return ret;
> +
> + uvc_device = handle->stream->dev;
Ouch... That's not nice very :-/
If you want to use the cleanup API, I think we could use guards with an
init function such as
struct uvc_device *__uvc_pm_get_init(struct uvc_device *dev, int *ret)
{
*ret = uvc_pm_get(dev);
return *ret ? NULL : dev;
}
You can use DEFINE_CLASS() instead of DEFINE_GUARD() to control the
arguments to the init function. Users of the guard could do
int ret;
guard(uvc_pm)(dev, &ret);
if (ret)
return ret;
...
Another, simpler option would be to replace returns with breaks in
uvc_v4l2_compat_ioctl32(). I'm tempted to do that in this patch, and
switching to the cleanup API as a patch on top if desired.
> +
> switch (cmd) {
> case UVCIOC_CTRL_MAP32:
> ret = uvc_v4l2_get_xu_mapping(&karg.xmap, up);
> @@ -1423,6 +1442,22 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
> }
> #endif
>
> +static long uvc_v4l2_unlocked_ioctl(struct file *file,
> + unsigned int cmd, unsigned long arg)
> +{
> + struct uvc_fh *handle = file->private_data;
> + int ret;
> +
> + ret = uvc_pm_get(handle->stream->dev);
> + if (ret)
> + return ret;
> +
> + ret = video_ioctl2(file, cmd, arg);
> +
> + uvc_pm_put(handle->stream->dev);
> + return ret;
> +}
> +
> static ssize_t uvc_v4l2_read(struct file *file, char __user *data,
> size_t count, loff_t *ppos)
> {
> @@ -1507,7 +1542,7 @@ const struct v4l2_file_operations uvc_fops = {
> .owner = THIS_MODULE,
> .open = uvc_v4l2_open,
> .release = uvc_v4l2_release,
> - .unlocked_ioctl = video_ioctl2,
> + .unlocked_ioctl = uvc_v4l2_unlocked_ioctl,
> #ifdef CONFIG_COMPAT
> .compat_ioctl32 = uvc_v4l2_compat_ioctl32,
> #endif
--
Regards,
Laurent Pinchart
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