Re: [PATCH v6 5/5] media: uvcvideo: Flush the control cache when we get an event

Hans de Goede
2024-12-09T11:03:55Z

Hi Ricardo,

On 3-Dec-24 10:20 PM, Ricardo Ribalda wrote:
> Asynchronous controls trigger an event when they have completed their
> operation.
>
> This can make that the control cached value does not match the value in
> the device.
>
> Let's flush the cache to be on the safe side.
>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

Thank you for your patch.

It seems that you have missed Laurent's reply asking to improve the commit message:

"Conceptually this change looks fine, but the commit message needs to
explain why this is safe to do without protecting ctrl->loaded with a
lock."

https://lore.kernel.org/linux-media/20241203203748.GD5196@pendragon.ideasonboard.com/

Or maybe the posting of this v6 and that reply have crossed each other.

Either way please post a new version addressing this comment.

Thanks & Regards,

Hans

> ---
> drivers/media/usb/uvc/uvc_ctrl.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 3dc9b7a49f64..db29e0e8bfd4 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1622,6 +1622,9 @@ void uvc_ctrl_status_event(struct uvc_video_chain *chain,
>
> mutex_lock(&chain->ctrl_mutex);
>
> + /* Flush the control cache, the data might have changed. */
> + ctrl->loaded = 0;
> +
> handle = ctrl->handle;
> if (handle)
> uvc_ctrl_set_handle(handle, ctrl, NULL);
>