From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Sakari Ailus <sakari.ailus@iki.fi>
Cc: linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Dafna Hirschfeld <dafna@fastmail.com>,
linux-rockchip@lists.infradead.org
Subject: Re: [PATCH v3 1/2] media: v4l2-subdev: Provide const-aware subdev state accessors
Date: Thu, 9 May 2024 00:02:45 +0300 [thread overview]
Message-ID: <20240508210245.GA13978@pendragon.ideasonboard.com> (raw)
In-Reply-To: <ZjvIGDaAAGK0WJo1@valkosipuli.retiisi.eu>
On Wed, May 08, 2024 at 06:44:40PM +0000, Sakari Ailus wrote:
> Hi Laurent,
>
> Thanks for the update.
>
> This is starting to look very nice. A few comments below...
Thanks :-)
> On Tue, May 07, 2024 at 07:19:06PM +0300, Laurent Pinchart wrote:
> > It would be useful to mark instances of v4l2_subdev_state structures as
> > const when code needs to access them read-only. This isn't currently
> > possible, as the v4l2_subdev_state_get_*() accessor functions take a
> > non-const pointer to the state.
> >
> > Use _Generic() to provide two different versions of the accessors, for
> > const and non-const states respectively. The former returns a const
> > pointer to the requested format, rectangle or interval, implementing
> > const-correctness. The latter returns a non-const pointer, preserving
> > the current behaviour for drivers.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> > Changes since v2:
> >
> > - Specify types explicitly in _Generic() expression
> > - Fix cast of value to const pointer
> >
> > Changes since v1:
> >
> > - Wrap the accessors with _Generic() using a single macro instead of
> > adding a _Generic() statement in each of them.
> > ---
> > include/media/v4l2-subdev.h | 40 +++++++++++++++++++++++++------------
> > 1 file changed, 27 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> > index e30c463d90e5..cd3e9e2ebe4d 100644
> > --- a/include/media/v4l2-subdev.h
> > +++ b/include/media/v4l2-subdev.h
> > @@ -1326,6 +1326,16 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd);
> > #define __v4l2_subdev_state_gen_call(NAME, _1, ARG, ...) \
> > __v4l2_subdev_state_get_ ## NAME ## ARG
> >
> > +/*
> > + * A macro to constify the return value of the state accessors when the state
> > + * parameter is const.
> > + */
> > +#define __v4l2_subdev_state_constify_call(state, value) \
>
> This function just changes the return value constness. How about calling it
> e.g. __v4l2_subdev_state_constify_ret instead?
Fine with me.
> Either way,
>
> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>
> > + _Generic(state, \
> > + const struct v4l2_subdev_state *: (const typeof(*(value)) *)(value), \
> > + struct v4l2_subdev_state *: (value) \
> > + )
> > +
> > /**
> > * v4l2_subdev_state_get_format() - Get pointer to a stream format
> > * @state: subdevice state
> > @@ -1340,16 +1350,17 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd);
> > */
> > /*
> > * Wrap v4l2_subdev_state_get_format(), allowing the function to be called with
> > - * two or three arguments. The purpose of the __v4l2_subdev_state_get_format()
> > + * two or three arguments. The purpose of the __v4l2_subdev_state_gen_call()
> > * macro below is to come up with the name of the function or macro to call,
> > * using the last two arguments (_stream and _pad). The selected function or
> > * macro is then called using the arguments specified by the caller. A similar
> > * arrangement is used for v4l2_subdev_state_crop() and
> > * v4l2_subdev_state_compose() below.
>
> These function names are missing _get after the prefix.
>
> Could you also add the interval function here, too?
>
> The would fit well for a separate patch.
I'll drop the change above and will fix the whole paragraph in a
separate patch.
> > */
> > -#define v4l2_subdev_state_get_format(state, pad, ...) \
> > - __v4l2_subdev_state_gen_call(format, ##__VA_ARGS__, , _pad) \
> > - (state, pad, ##__VA_ARGS__)
> > +#define v4l2_subdev_state_get_format(state, pad, ...) \
> > + __v4l2_subdev_state_constify_call(state, \
> > + __v4l2_subdev_state_gen_call(format, ##__VA_ARGS__, , _pad) \
> > + ((struct v4l2_subdev_state *)state, pad, ##__VA_ARGS__))
> > #define __v4l2_subdev_state_get_format_pad(state, pad) \
> > __v4l2_subdev_state_get_format(state, pad, 0)
> > struct v4l2_mbus_framefmt *
> > @@ -1368,9 +1379,10 @@ __v4l2_subdev_state_get_format(struct v4l2_subdev_state *state,
> > * For stream-unaware drivers the crop rectangle for the corresponding pad is
> > * returned. If the pad does not exist, NULL is returned.
> > */
> > -#define v4l2_subdev_state_get_crop(state, pad, ...) \
> > - __v4l2_subdev_state_gen_call(crop, ##__VA_ARGS__, , _pad) \
> > - (state, pad, ##__VA_ARGS__)
> > +#define v4l2_subdev_state_get_crop(state, pad, ...) \
> > + __v4l2_subdev_state_constify_call(state, \
> > + __v4l2_subdev_state_gen_call(crop, ##__VA_ARGS__, , _pad) \
> > + ((struct v4l2_subdev_state *)state, pad, ##__VA_ARGS__))
> > #define __v4l2_subdev_state_get_crop_pad(state, pad) \
> > __v4l2_subdev_state_get_crop(state, pad, 0)
> > struct v4l2_rect *
> > @@ -1389,9 +1401,10 @@ __v4l2_subdev_state_get_crop(struct v4l2_subdev_state *state, unsigned int pad,
> > * For stream-unaware drivers the compose rectangle for the corresponding pad is
> > * returned. If the pad does not exist, NULL is returned.
> > */
> > -#define v4l2_subdev_state_get_compose(state, pad, ...) \
> > - __v4l2_subdev_state_gen_call(compose, ##__VA_ARGS__, , _pad) \
> > - (state, pad, ##__VA_ARGS__)
> > +#define v4l2_subdev_state_get_compose(state, pad, ...) \
> > + __v4l2_subdev_state_constify_call(state, \
> > + __v4l2_subdev_state_gen_call(compose, ##__VA_ARGS__, , _pad) \
> > + ((struct v4l2_subdev_state *)state, pad, ##__VA_ARGS__))
> > #define __v4l2_subdev_state_get_compose_pad(state, pad) \
> > __v4l2_subdev_state_get_compose(state, pad, 0)
> > struct v4l2_rect *
> > @@ -1410,9 +1423,10 @@ __v4l2_subdev_state_get_compose(struct v4l2_subdev_state *state,
> > * For stream-unaware drivers the frame interval for the corresponding pad is
> > * returned. If the pad does not exist, NULL is returned.
> > */
> > -#define v4l2_subdev_state_get_interval(state, pad, ...) \
> > - __v4l2_subdev_state_gen_call(interval, ##__VA_ARGS__, , _pad) \
> > - (state, pad, ##__VA_ARGS__)
> > +#define v4l2_subdev_state_get_interval(state, pad, ...) \
> > + __v4l2_subdev_state_constify_call(state, \
> > + __v4l2_subdev_state_gen_call(interval, ##__VA_ARGS__, , _pad) \
> > + ((struct v4l2_subdev_state *)state, pad, ##__VA_ARGS__))
> > #define __v4l2_subdev_state_get_interval_pad(state, pad) \
> > __v4l2_subdev_state_get_interval(state, pad, 0)
> > struct v4l2_fract *
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2024-05-08 21:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 16:19 [PATCH v3 0/2] media: v4l2-subdev: Support const-awareness in state accessors Laurent Pinchart
2024-05-07 16:19 ` [PATCH v3 1/2] media: v4l2-subdev: Provide const-aware subdev " Laurent Pinchart
2024-05-08 18:44 ` Sakari Ailus
2024-05-08 18:48 ` Tomi Valkeinen
2024-05-08 21:02 ` Laurent Pinchart [this message]
2024-05-07 16:19 ` [PATCH v3 2/2] media: rkisp1: Mark subdev state pointers as const Laurent Pinchart
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