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Message-ID: <20240926143940.GI21788@pendragon.ideasonboard.com>
Date: Thu, 26 Sep 2024 17:39:40 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
Guenter Roeck <linux@...ck-us.net>,
Tomasz Figa <tfiga@...omium.org>,
Alan Stern <stern@...land.harvard.edu>,
Hans Verkuil <hverkuil-cisco@...all.nl>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
Sean Paul <seanpaul@...omium.org>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH v7 1/3] media: uvcvideo: Refactor the status irq API
Hi Ricardo,
Thank you for the patch.
On Thu, Sep 26, 2024 at 05:49:57AM +0000, Ricardo Ribalda wrote:
> There are two different use-cases of uvc_status():
>
> - adding/removing a user when the camera is open/closed
> - stopping/starting when the camera is suspended/resumed
>
> Make the API reflect these two use-cases and move all the refcounting
> and locking logic to the uvc_status.c file.
>
> No functional change is expected from this patch.
>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
> drivers/media/usb/uvc/uvc_driver.c | 13 ++--------
> drivers/media/usb/uvc/uvc_status.c | 53 ++++++++++++++++++++++++++++++++++++--
> drivers/media/usb/uvc/uvc_v4l2.c | 22 +++++-----------
> drivers/media/usb/uvc/uvcvideo.h | 10 ++++---
> 4 files changed, 65 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index f0febdc08c2d..31e8942f1ef8 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -2116,7 +2116,6 @@ static int uvc_probe(struct usb_interface *intf,
> INIT_LIST_HEAD(&dev->streams);
> kref_init(&dev->ref);
> atomic_set(&dev->nmappings, 0);
> - mutex_init(&dev->lock);
>
> dev->udev = usb_get_dev(udev);
> dev->intf = usb_get_intf(intf);
> @@ -2288,10 +2287,7 @@ static int uvc_suspend(struct usb_interface *intf, pm_message_t message)
> /* Controls are cached on the fly so they don't need to be saved. */
> if (intf->cur_altsetting->desc.bInterfaceSubClass ==
> UVC_SC_VIDEOCONTROL) {
> - mutex_lock(&dev->lock);
> - if (dev->users)
> - uvc_status_stop(dev);
> - mutex_unlock(&dev->lock);
> + uvc_status_suspend(dev);
> return 0;
> }
>
> @@ -2322,12 +2318,7 @@ static int __uvc_resume(struct usb_interface *intf, int reset)
> return ret;
> }
>
> - mutex_lock(&dev->lock);
> - if (dev->users)
> - ret = uvc_status_start(dev, GFP_NOIO);
> - mutex_unlock(&dev->lock);
> -
> - return ret;
> + return uvc_status_resume(dev);
> }
>
> list_for_each_entry(stream, &dev->streams, list) {
> diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> index a78a88c710e2..e438ae5af2e8 100644
> --- a/drivers/media/usb/uvc/uvc_status.c
> +++ b/drivers/media/usb/uvc/uvc_status.c
> @@ -257,6 +257,8 @@ int uvc_status_init(struct uvc_device *dev)
> unsigned int pipe;
> int interval;
>
> + mutex_init(&dev->status_lock);
> +
> if (ep == NULL)
> return 0;
>
> @@ -302,18 +304,22 @@ void uvc_status_cleanup(struct uvc_device *dev)
> kfree(dev->status);
> }
>
> -int uvc_status_start(struct uvc_device *dev, gfp_t flags)
> +static int uvc_status_start(struct uvc_device *dev, gfp_t flags)
> {
> + lockdep_assert_held(&dev->status_lock);
> +
> if (dev->int_urb == NULL)
> return 0;
>
> return usb_submit_urb(dev->int_urb, flags);
> }
>
> -void uvc_status_stop(struct uvc_device *dev)
> +static void uvc_status_stop(struct uvc_device *dev)
> {
> struct uvc_ctrl_work *w = &dev->async_ctrl;
>
> + lockdep_assert_held(&dev->status_lock);
> +
> /*
> * Prevent the asynchronous control handler from requeing the URB. The
> * barrier is needed so the flush_status change is visible to other
> @@ -350,3 +356,46 @@ void uvc_status_stop(struct uvc_device *dev)
> */
> smp_store_release(&dev->flush_status, false);
> }
> +
> +int uvc_status_resume(struct uvc_device *dev)
> +{
> + guard(mutex)(&dev->status_lock);
> +
> + if (dev->status_users)
> + return uvc_status_start(dev, GFP_NOIO);
Double space afer return. I'll fix when applying.
> +
> + return 0;
> +}
> +
> +void uvc_status_suspend(struct uvc_device *dev)
> +{
> + guard(mutex)(&dev->status_lock);
> +
> + if (dev->status_users)
> + uvc_status_stop(dev);
> +}
> +
> +int uvc_status_get(struct uvc_device *dev)
> +{
> + int ret = 0;
> +
> + guard(mutex)(&dev->status_lock);
> +
> + if (!dev->status_users)
> + ret = uvc_status_start(dev, GFP_KERNEL);
> + if (!ret)
> + dev->status_users++;
Thanks for the scoped guard, we can write
if (!dev->status_users) {
int ret = uvc_status_start(dev, GFP_KERNEL);
if (ret)
return ret;
}
dev->status_users++;
return 0;
which I think is nicer to read. If that's fine with you I'll do this
locally, not need to a new version.
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> +
> + return ret;
> +}
> +
> +void uvc_status_put(struct uvc_device *dev)
> +{
> + guard(mutex)(&dev->status_lock);
> +
> + if (dev->status_users == 1)
> + uvc_status_stop(dev);
> + WARN_ON(!dev->status_users);
> + if (dev->status_users)
> + dev->status_users--;
> +}
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index f4988f03640a..97c5407f6603 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -628,20 +628,13 @@ static int uvc_v4l2_open(struct file *file)
> return -ENOMEM;
> }
>
> - mutex_lock(&stream->dev->lock);
> - if (stream->dev->users == 0) {
> - ret = uvc_status_start(stream->dev, GFP_KERNEL);
> - if (ret < 0) {
> - mutex_unlock(&stream->dev->lock);
> - usb_autopm_put_interface(stream->dev->intf);
> - kfree(handle);
> - return ret;
> - }
> + ret = uvc_status_get(stream->dev);
> + if (ret) {
> + usb_autopm_put_interface(stream->dev->intf);
> + kfree(handle);
> + return ret;
> }
>
> - stream->dev->users++;
> - mutex_unlock(&stream->dev->lock);
> -
> v4l2_fh_init(&handle->vfh, &stream->vdev);
> v4l2_fh_add(&handle->vfh);
> handle->chain = stream->chain;
> @@ -670,10 +663,7 @@ static int uvc_v4l2_release(struct file *file)
> kfree(handle);
> file->private_data = NULL;
>
> - mutex_lock(&stream->dev->lock);
> - if (--stream->dev->users == 0)
> - uvc_status_stop(stream->dev);
> - mutex_unlock(&stream->dev->lock);
> + uvc_status_put(stream->dev);
>
> usb_autopm_put_interface(stream->dev->intf);
> return 0;
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index b7d24a853ce4..07f9921d83f2 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -563,8 +563,6 @@ struct uvc_device {
>
> const struct uvc_device_info *info;
>
> - struct mutex lock; /* Protects users */
> - unsigned int users;
> atomic_t nmappings;
>
> /* Video control interface */
> @@ -586,6 +584,8 @@ struct uvc_device {
> struct usb_host_endpoint *int_ep;
> struct urb *int_urb;
> struct uvc_status *status;
> + struct mutex status_lock; /* Protects status_users */
> + unsigned int status_users;
> bool flush_status;
>
> struct input_dev *input;
> @@ -752,8 +752,10 @@ int uvc_register_video_device(struct uvc_device *dev,
> int uvc_status_init(struct uvc_device *dev);
> void uvc_status_unregister(struct uvc_device *dev);
> void uvc_status_cleanup(struct uvc_device *dev);
> -int uvc_status_start(struct uvc_device *dev, gfp_t flags);
> -void uvc_status_stop(struct uvc_device *dev);
> +int uvc_status_resume(struct uvc_device *dev);
> +void uvc_status_suspend(struct uvc_device *dev);
> +int uvc_status_get(struct uvc_device *dev);
> +void uvc_status_put(struct uvc_device *dev);
>
> /* Controls */
> extern const struct v4l2_subscribed_event_ops uvc_ctrl_sub_ev_ops;
--
Regards,
Laurent Pinchart
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