[PATCH] v4l2-dev.h: fix symbol collision in media_entity_to_video_device()

[PATCH] v4l2-dev.h: fix symbol collision in media_entity_to_video_device()

[Niklas Söderlund]

A recent change to the media_entity_to_video_device() macro breaks some
use-cases for the macro due to a symbol collision. Before the change
this worked:

    vdev = media_entity_to_video_device(link->sink->entity);

While after the change it results in a compiler error "error: 'struct
video_device' has no member named 'link'; did you mean 'lock'?". While
the following still works after the change.

    struct media_entity *entity = link->sink->entity;
    vdev = media_entity_to_video_device(entity);

Fix the collision by renaming the macro argument to 'media_entity'.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
---
 include/media/v4l2-dev.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Hi Mauro,

As the offending commit is not yet upstream and I'm not sure if the 
commit ids in the media-tree are stable. If they are please attach the 
following fixes tag.

Fixes: 69b925c5fc36d8f1 ("media: v4l2-dev.h: add kernel-doc to two macros")

Regards,
// Niklas

diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index 267fd2bed17bd3c1..f0fc1ebda47244b3 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -298,10 +298,10 @@ struct video_device
  * media_entity_to_video_device - Returns a &struct video_device from
  *	the &struct media_entity embedded on it.
  *
- * @entity: pointer to &struct media_entity
+ * @media_entity: pointer to &struct media_entity
  */
-#define media_entity_to_video_device(entity) \
-	container_of(entity, struct video_device, entity)
+#define media_entity_to_video_device(media_entity) \
+	container_of(media_entity, struct video_device, entity)
 
 /**
  * to_video_device - Returns a &struct video_device from the
-- 
2.15.1

Re: [PATCH] v4l2-dev.h: fix symbol collision in media_entity_to_video_device()

[Geert Uytterhoeven]

Hi Niklas,

On Thu, Jan 25, 2018 at 1:34 AM, Niklas Söderlund
<niklas.soderlund+renesas@ragnatech.se> wrote:
> A recent change to the media_entity_to_video_device() macro breaks some
> use-cases for the macro due to a symbol collision. Before the change
> this worked:
>
>     vdev = media_entity_to_video_device(link->sink->entity);
>
> While after the change it results in a compiler error "error: 'struct
> video_device' has no member named 'link'; did you mean 'lock'?". While
> the following still works after the change.
>
>     struct media_entity *entity = link->sink->entity;
>     vdev = media_entity_to_video_device(entity);
>
> Fix the collision by renaming the macro argument to 'media_entity'.

Thanks!
Given there also exists a "struct media_entity", using "_media_entity" seems
safe to me.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] v4l2-dev.h: fix symbol collision in media_entity_to_video_device()

[Sakari Ailus]

Hi guys,

On Thu, Jan 25, 2018 at 08:59:35AM +0100, Geert Uytterhoeven wrote:
> Hi Niklas,
> 
> On Thu, Jan 25, 2018 at 1:34 AM, Niklas S�derlund
> <niklas.soderlund+renesas@ragnatech.se> wrote:
> > A recent change to the media_entity_to_video_device() macro breaks some
> > use-cases for the macro due to a symbol collision. Before the change
> > this worked:
> >
> >     vdev = media_entity_to_video_device(link->sink->entity);
> >
> > While after the change it results in a compiler error "error: 'struct
> > video_device' has no member named 'link'; did you mean 'lock'?". While
> > the following still works after the change.
> >
> >     struct media_entity *entity = link->sink->entity;
> >     vdev = media_entity_to_video_device(entity);
> >
> > Fix the collision by renaming the macro argument to 'media_entity'.
> 
> Thanks!
> Given there also exists a "struct media_entity", using "_media_entity" seems
> safe to me.

That doesn't matter, does it? As long as the macro argument is used as a
field name of a struct. I.e. "__entity" would be fine, as well as "e". I'd
vote for __entity. :-)

In any case,

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>

-- 
Sakari Ailus
e-mail: sakari.ailus@iki.fi

Re: [PATCH] v4l2-dev.h: fix symbol collision in media_entity_to_video_device()

[Mauro Carvalho Chehab]

Hi Niklas,

Em Thu, 25 Jan 2018 01:34:30 +0100
Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> escreveu:

> A recent change to the media_entity_to_video_device() macro breaks some
> use-cases for the macro due to a symbol collision. Before the change
> this worked:
> 
>     vdev = media_entity_to_video_device(link->sink->entity);
> 
> While after the change it results in a compiler error "error: 'struct
> video_device' has no member named 'link'; did you mean 'lock'?". While
> the following still works after the change.
> 
>     struct media_entity *entity = link->sink->entity;
>     vdev = media_entity_to_video_device(entity);
> 
> Fix the collision by renaming the macro argument to 'media_entity'.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
>  include/media/v4l2-dev.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> Hi Mauro,
> 
> As the offending commit is not yet upstream and I'm not sure if the 
> commit ids in the media-tree are stable. If they are please attach the 
> following fixes tag.

They are. 

> 
> Fixes: 69b925c5fc36d8f1 ("media: v4l2-dev.h: add kernel-doc to two macros")
> 
> Regards,
> // Niklas
> 
> diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> index 267fd2bed17bd3c1..f0fc1ebda47244b3 100644
> --- a/include/media/v4l2-dev.h
> +++ b/include/media/v4l2-dev.h
> @@ -298,10 +298,10 @@ struct video_device
>   * media_entity_to_video_device - Returns a &struct video_device from
>   *	the &struct media_entity embedded on it.
>   *
> - * @entity: pointer to &struct media_entity
> + * @media_entity: pointer to &struct media_entity
>   */
> -#define media_entity_to_video_device(entity) \
> -	container_of(entity, struct video_device, entity)
> +#define media_entity_to_video_device(media_entity) \
> +	container_of(media_entity, struct video_device, entity)

Instead, the best would be to use __entity (or __media_entity).
That would very likely prevent future conflicts.

>  
>  /**
>   * to_video_device - Returns a &struct video_device from the




Cheers,
Mauro