linux-kernel - Re: [PATCH] media: v4l2-subdev.h: drop the guard CONFIG_VIDEO_V4L2_SUBDEV_API for v4l2_subdev_get_try

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Message-ID: <CA+V-a8s-mP+Fjok2s_nDUAOb4vN3RWyRc5VHuZqPdk4pJtv03A@mail.gmail.com>
Date:	Sat, 29 Nov 2014 18:30:09 +0000
From:	Prabhakar Lad <prabhakar.csengg@...il.com>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	Hans Verkuil <hverkuil@...all.nl>,
	linux-media <linux-media@...r.kernel.org>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Sakari Ailus <sakari.ailus@....fi>
Subject: Re: [PATCH] media: v4l2-subdev.h: drop the guard CONFIG_VIDEO_V4L2_SUBDEV_API
 for v4l2_subdev_get_try_*()

Hi Laurent,

On Tue, Nov 18, 2014 at 6:07 PM, Sakari Ailus <sakari.ailus@....fi> wrote:
> Hi Hans and Prabhakar,
>
> On Tue, Nov 18, 2014 at 10:39:24AM +0100, Hans Verkuil wrote:
>> On 11/17/14 11:41, Lad, Prabhakar wrote:
>> > this patch removes the guard CONFIG_VIDEO_V4L2_SUBDEV_API
>> > for v4l2_subdev_get_try_*() functions.
>> > In cases where a subdev using v4l2_subdev_get_try_*() calls
>> > internally and the bridge using subdev pad ops which is
>> > not MC aware forces to select MEDIA_CONTROLLER, as
>> > VIDEO_V4L2_SUBDEV_API is dependent on it.
>> >
>> > Signed-off-by: Lad, Prabhakar <prabhakar.csengg@...il.com>
>> > ---
>> >  include/media/v4l2-subdev.h | 2 --
>> >  1 file changed, 2 deletions(-)
>> >
>> > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>> > index 5860292..076ca11 100644
>> > --- a/include/media/v4l2-subdev.h
>> > +++ b/include/media/v4l2-subdev.h
>> > @@ -642,7 +642,6 @@ struct v4l2_subdev_fh {
>> >  #define to_v4l2_subdev_fh(fh)      \
>> >     container_of(fh, struct v4l2_subdev_fh, vfh)
>> >
>> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>> >  #define __V4L2_SUBDEV_MK_GET_TRY(rtype, fun_name, field_name)              \
>> >     static inline struct rtype *                                    \
>> >     v4l2_subdev_get_try_##fun_name(struct v4l2_subdev_fh *fh,       \
>> > @@ -656,7 +655,6 @@ struct v4l2_subdev_fh {
>> >  __V4L2_SUBDEV_MK_GET_TRY(v4l2_mbus_framefmt, format, try_fmt)
>> >  __V4L2_SUBDEV_MK_GET_TRY(v4l2_rect, crop, try_crop)
>> >  __V4L2_SUBDEV_MK_GET_TRY(v4l2_rect, compose, try_compose)
>> > -#endif
>> >
>> >  extern const struct v4l2_file_operations v4l2_subdev_fops;
>> >
>> >
>>
>> The problem is that v4l2_subdev_get_try_*() needs a v4l2_subdev_fh which
>> you don't have if CONFIG_VIDEO_V4L2_SUBDEV_API is not defined. So I don't
>> see how removing the guards help with that.
>>
>> What can be done is that if CONFIG_VIDEO_V4L2_SUBDEV_API is not defined,
>> then these functions return NULL.
>
> Sure. That's a better choice than removing the config option dependency of
> the fields struct v4l2_subdev.
>
>> BTW, one patch I will very happily accept is one where the __V4L2_SUBDEV_MK_GET_TRY
>> is removed and these three try functions are just written as proper
>> static inlines. I find it very obfuscated code.
>
> I originally wrote them like that in order to avoid writing essentially the
> same code three times over. If there will be more targets, the same repeats
> further, should one write those functions open for all different macro
> arguments. That's why it was a macro to begin with.
>
>> In addition, because it is a macro you won't find the function definitions
>> if you grep on the function name.
>
> True as well. You could simply change the macro to include the full function
> name. This was not suggested in review back then AFAIR.
>
>> But any functional changes here need to be Acked by Laurent first.
>

How do you want me to proceed on this ?

Thanks,
--Prabhakar Lad
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