media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

[PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Desnes Nunes 3 months, 1 week ago

This fixes the following compilation failure: "error: ‘for’ loop
initial declarations are only allowed in C99 or C11 mode"

Cc: stable@vger.kernel.org
Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
Signed-off-by: Desnes Nunes <desnesn@redhat.com>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 44b6513c5264..532615d8484b 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
 void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
 {
 	struct uvc_entity *entity;
-	int i;
+	unsigned int i;
 
 	guard(mutex)(&handle->chain->ctrl_mutex);
 
@@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
 		return;
 
 	list_for_each_entry(entity, &handle->chain->dev->entities, list) {
-		for (unsigned int i = 0; i < entity->ncontrols; ++i) {
+		for (i = 0; i < entity->ncontrols; ++i) {
 			if (entity->controls[i].handle != handle)
 				continue;
 			uvc_ctrl_set_handle(handle, &entity->controls[i], NULL);
-- 
2.49.0

Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Greg KH 3 months, 1 week ago

On Mon, Jun 30, 2025 at 12:01:06PM -0300, Desnes Nunes wrote:
> This fixes the following compilation failure: "error: ‘for’ loop
> initial declarations are only allowed in C99 or C11 mode"
> 
> Cc: stable@vger.kernel.org
> Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 44b6513c5264..532615d8484b 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
>  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
>  {
>  	struct uvc_entity *entity;
> -	int i;
> +	unsigned int i;
>  
>  	guard(mutex)(&handle->chain->ctrl_mutex);

If your compiler can handle this guard(mutex) line, then:

>  
> @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
>  		return;
>  
>  	list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> -		for (unsigned int i = 0; i < entity->ncontrols; ++i) {

It can also handle that line.

Are you sure you are using a sane compiler?

confused,

greg k-h

Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Desnes Nunes 3 months, 1 week ago

Hello Greg,

The compiler is sane, but I ran into this while backporting fixes to
an old codebase that still uses C89 due to legacy support reasons.
Furthermore, you're right; there is no guard() in my code base, thus I
had to backport guard() with the old mutex lock/unlock calls used
prior to guard().
Indeed - will focus on all of what has been said on the v2.

Thanks for the review Greg,

On Mon, Jun 30, 2025 at 12:42 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Mon, Jun 30, 2025 at 12:01:06PM -0300, Desnes Nunes wrote:
> > This fixes the following compilation failure: "error: ‘for’ loop
> > initial declarations are only allowed in C99 or C11 mode"
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> > Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 44b6513c5264..532615d8484b 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> >  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >  {
> >       struct uvc_entity *entity;
> > -     int i;
> > +     unsigned int i;
> >
> >       guard(mutex)(&handle->chain->ctrl_mutex);
>
> If your compiler can handle this guard(mutex) line, then:
>
> >
> > @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >               return;
> >
> >       list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> > -             for (unsigned int i = 0; i < entity->ncontrols; ++i) {
>
> It can also handle that line.
>
> Are you sure you are using a sane compiler?
>
> confused,
>
> greg k-h
>


-- 
Desnes Nunes

Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Ricardo Ribalda 3 months, 1 week ago

Hi Desdes

How did you trigger this build warning? I believe we use C11

https://www.kernel.org/doc/html/latest/process/programming-language.html


Regards!

On Mon, 30 Jun 2025 at 17:07, Desnes Nunes <desnesn@redhat.com> wrote:
>
> This fixes the following compilation failure: "error: ‘for’ loop
> initial declarations are only allowed in C99 or C11 mode"
>
> Cc: stable@vger.kernel.org
> Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 44b6513c5264..532615d8484b 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
>  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
>  {
>         struct uvc_entity *entity;
> -       int i;
> +       unsigned int i;
>
>         guard(mutex)(&handle->chain->ctrl_mutex);
>
> @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
>                 return;
>
>         list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> -               for (unsigned int i = 0; i < entity->ncontrols; ++i) {
> +               for (i = 0; i < entity->ncontrols; ++i) {
>                         if (entity->controls[i].handle != handle)
>                                 continue;
>                         uvc_ctrl_set_handle(handle, &entity->controls[i], NULL);
> --
> 2.49.0
>
>


-- 
Ricardo Ribalda

Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Desnes Nunes 3 months, 1 week ago

Hello Ricardo,

I triggered this build error while working in an older codebase that
uses C89 due to legacy support reasons.
Indeed - will focus on submitting C11 compatible fixes even when
working on older codebases.

Thanks for the review Ricardo,


On Mon, Jun 30, 2025 at 12:16 PM Ricardo Ribalda <ribalda@chromium.org> wrote:
>
> Hi Desdes
>
> How did you trigger this build warning? I believe we use C11
>
> https://www.kernel.org/doc/html/latest/process/programming-language.html
>
>
> Regards!
>
> On Mon, 30 Jun 2025 at 17:07, Desnes Nunes <desnesn@redhat.com> wrote:
> >
> > This fixes the following compilation failure: "error: ‘for’ loop
> > initial declarations are only allowed in C99 or C11 mode"
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> > Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 44b6513c5264..532615d8484b 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> >  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >  {
> >         struct uvc_entity *entity;
> > -       int i;
> > +       unsigned int i;
> >
> >         guard(mutex)(&handle->chain->ctrl_mutex);
> >
> > @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >                 return;
> >
> >         list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> > -               for (unsigned int i = 0; i < entity->ncontrols; ++i) {
> > +               for (i = 0; i < entity->ncontrols; ++i) {
> >                         if (entity->controls[i].handle != handle)
> >                                 continue;
> >                         uvc_ctrl_set_handle(handle, &entity->controls[i], NULL);
> > --
> > 2.49.0
> >
> >
>
>
> --
> Ricardo Ribalda
>


-- 
Desnes Nunes

Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Laurent Pinchart 3 months, 1 week ago

On Mon, Jun 30, 2025 at 05:15:38PM +0200, Ricardo Ribalda wrote:
> Hi Desdes
> 
> How did you trigger this build warning? I believe we use C11
> 
> https://www.kernel.org/doc/html/latest/process/programming-language.html

Note that the local declaration of the loop counter shadows the global
one. I would have expected a different compiler warning though.

The shadowing was introduced by

commit 10acb9101355484c3e4f2625003cd1b6c203cfe4
Author: Ricardo Ribalda <ribalda@chromium.org>
Date:   Thu Mar 27 21:05:29 2025 +0000

    media: uvcvideo: Increase/decrease the PM counter per IOCTL

and I think it should be fixed (while at it, with an unsigned int local
loop counter instead of a signed int) as it's not a good practice.

> On Mon, 30 Jun 2025 at 17:07, Desnes Nunes <desnesn@redhat.com> wrote:
> >
> > This fixes the following compilation failure: "error: ‘for’ loop
> > initial declarations are only allowed in C99 or C11 mode"
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> > Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 44b6513c5264..532615d8484b 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> >  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >  {
> >         struct uvc_entity *entity;
> > -       int i;
> > +       unsigned int i;
> >
> >         guard(mutex)(&handle->chain->ctrl_mutex);
> >
> > @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >                 return;
> >
> >         list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> > -               for (unsigned int i = 0; i < entity->ncontrols; ++i) {
> > +               for (i = 0; i < entity->ncontrols; ++i) {
> >                         if (entity->controls[i].handle != handle)
> >                                 continue;
> >                         uvc_ctrl_set_handle(handle, &entity->controls[i], NULL);

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: uvcvideo: fix build error in uvc_ctrl_cleanup_fh

Posted by Desnes Nunes 3 months, 1 week ago

Hello Laurent,

Yes, I did see that commit and will send a v2 to properly address the
variable shadowing following C11 standards.

Thanks for the review Laurent,

On Mon, Jun 30, 2025 at 12:30 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Mon, Jun 30, 2025 at 05:15:38PM +0200, Ricardo Ribalda wrote:
> > Hi Desdes
> >
> > How did you trigger this build warning? I believe we use C11
> >
> > https://www.kernel.org/doc/html/latest/process/programming-language.html
>
> Note that the local declaration of the loop counter shadows the global
> one. I would have expected a different compiler warning though.
>
> The shadowing was introduced by
>
> commit 10acb9101355484c3e4f2625003cd1b6c203cfe4
> Author: Ricardo Ribalda <ribalda@chromium.org>
> Date:   Thu Mar 27 21:05:29 2025 +0000
>
>     media: uvcvideo: Increase/decrease the PM counter per IOCTL
>
> and I think it should be fixed (while at it, with an unsigned int local
> loop counter instead of a signed int) as it's not a good practice.
>
> > On Mon, 30 Jun 2025 at 17:07, Desnes Nunes <desnesn@redhat.com> wrote:
> > >
> > > This fixes the following compilation failure: "error: ‘for’ loop
> > > initial declarations are only allowed in C99 or C11 mode"
> > >
> > > Cc: stable@vger.kernel.org
> > > Fixes: 221cd51efe45 ("media: uvcvideo: Remove dangling pointers")
> > > Signed-off-by: Desnes Nunes <desnesn@redhat.com>
> > > ---
> > >  drivers/media/usb/uvc/uvc_ctrl.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > > index 44b6513c5264..532615d8484b 100644
> > > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > > @@ -3260,7 +3260,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> > >  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> > >  {
> > >         struct uvc_entity *entity;
> > > -       int i;
> > > +       unsigned int i;
> > >
> > >         guard(mutex)(&handle->chain->ctrl_mutex);
> > >
> > > @@ -3268,7 +3268,7 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> > >                 return;
> > >
> > >         list_for_each_entry(entity, &handle->chain->dev->entities, list) {
> > > -               for (unsigned int i = 0; i < entity->ncontrols; ++i) {
> > > +               for (i = 0; i < entity->ncontrols; ++i) {
> > >                         if (entity->controls[i].handle != handle)
> > >                                 continue;
> > >                         uvc_ctrl_set_handle(handle, &entity->controls[i], NULL);
>
> --
> Regards,
>
> Laurent Pinchart
>


-- 
Desnes Nunes