linux-kernel - Re: [PATCH v2 4/4] media: uvcvideo: Remove redundant NULL assignment

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Message-ID: <CANiDSCvb8OCGJjggermRPeD6R2Rt79hMuwF6xc6YQvvSqUNObA@mail.gmail.com>
Date: Thu, 28 Nov 2024 22:34:38 +0100
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Hans de Goede <hdegoede@...hat.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Guennadi Liakhovetski <guennadi.liakhovetski@...el.com>, 
	Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] media: uvcvideo: Remove redundant NULL assignment

Hi

On Thu, 28 Nov 2024 at 22:26, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Wed, Nov 27, 2024 at 12:14:52PM +0000, Ricardo Ribalda wrote:
> > ctrl->handle will only be different than NULL for controls that have
> > mappings. This is because that assignment is only done inside
> > uvc_ctrl_set() for mapped controls.
>
> That seems right. I checked the unplug paths, and the mappings are
> destroyed from uvc_delete(), after all file handles get closed.
>
> I think this patch should go first in the series, as otherwise there's a
> temporary state where you rely on handle never being touched without
> holding the proper lock, and this code path violates that requirement.
> Is there anything I may be missing that would cause issues with
> bisection if I move this patch at the beginning of the series ?
>

You probably want to add the Cc: stable and Fixes: tags if you make
this patch the first one.

> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 99ddc5e9dff8..b9c9ff629ab6 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -1645,10 +1645,8 @@ bool uvc_ctrl_status_event_async(struct urb *urb, struct uvc_video_chain *chain,
> >       struct uvc_device *dev = chain->dev;
> >       struct uvc_ctrl_work *w = &dev->async_ctrl;
> >
> > -     if (list_empty(&ctrl->info.mappings)) {
> > -             ctrl->handle = NULL;
> > +     if (list_empty(&ctrl->info.mappings))
> >               return false;
> > -     }
> >
> >       w->data = data;
> >       w->urb = urb;
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda