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

Ricardo Ribalda
2024-12-09T11:31:35Z

Hi Hans

On Mon, 9 Dec 2024 at 12:03, Hans de Goede <hdegoede@redhat.com> wrote:
>
> 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.

In this v6 I moved loaded=0 from uvc_ctrl_status_event_async() to
uvc_ctrl_status_event()

Now setting loaded=0 is just after mutex_lock(&chain->ctrl_mutex);

Do we need a new version?

>
> 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);
> >
>

--
Ricardo Ribalda