Re: [PATCH] media: uvcvideo: avoid variable shadowing in uvc_ctrl_cleanup_fh

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Jul 01, 2025 at 02:20:53PM -0300, Desnes Nunes wrote:
> On Tue, Jul 1, 2025 at 1:48 PM Ricardo Ribalda <ribalda@chromium.org> wrote:
> > On Tue, 1 Jul 2025 at 16:59, Desnes Nunes <desnesn@redhat.com> wrote:
> > >
> > > This avoids a variable loop shadowing occurring between the local loop
> > > iterating through the uvc_entity's controls and the global one going
> > > through the pending async controls of the file handle
> > >
> > > Fixes: 10acb9101355 ("media: uvcvideo: Increase/decrease the PM counter per IOCTL")
> > If you add a fixes you need to add
> > Cc: stable@kernel.org
> 
> Thanks for letting me know
> 
> > Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
> > > Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> > > ---
> > >  drivers/media/usb/uvc/uvc_ctrl.c | 3 +--
> > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > > index 44b6513c5264..91cc874da798 100644
> > > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > > @@ -3260,7 +3260,6 @@ 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);
> > >
> > > @@ -3278,7 +3277,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> > >         if (!WARN_ON(handle->pending_async_ctrls))
> > >                 return;
> > >
> > > -       for (i = 0; i < handle->pending_async_ctrls; i++)
> >
> > nitpick: I would have called the variable i, not j.  For me j usually
> > means nested loop. But up to you
> 
> Noted - I used a different variable name because I wanted to
> differentiate the loops.

Variable declaration in the loop statement is relatively new in the
kernel, so there's no consensus yet (to my knowledge) on clear coding
styles, but I would have simply used the same variable name in both
loops, with two separate declarations:

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 303b7509ec47..6b9486749c3f 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -3299,7 +3299,6 @@ 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);

@@ -3317,7 +3316,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
 	if (!WARN_ON(handle->pending_async_ctrls))
 		return;

-	for (i = 0; i < handle->pending_async_ctrls; i++)
+	for (unsigned int i = 0; i < handle->pending_async_ctrls; i++)
 		uvc_pm_put(handle->stream->dev);
 }

Is there a downside to this ?

> > I am also not against your first version with a different commit message.
> 
> Third time's a charm then!
> 
> Will send a v2 with the first version having this commit message.
> 
> Thanks for the review Ricardo,

-- 
Regards,

Laurent Pinchart