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media: v4l2-subdev: Provide const-aware subdev state accessors

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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>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
[Sakari Ailus: Drop the word "below" from the text.]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
This commit is contained in:
Laurent Pinchart 2024-05-09 00:40:43 +03:00 committed by Hans Verkuil
parent e73412fdeb
commit 85af84852f
1 changed files with 35 additions and 17 deletions
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52
include/media/v4l2-subdev.h
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@ -1337,6 +1337,16 @@ 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_ret(state, value) \
_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
@ -1352,15 +1362,20 @@ 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_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(), v4l2_subdev_state_compose()
* and v4l2_subdev_state_get_interval() below.
* macro 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. The
* __v4l2_subdev_state_constify_ret() macro constifies the returned pointer
* when the state is const, allowing the state accessors to guarantee
* const-correctness in all cases.
*
* A similar arrangement is used for v4l2_subdev_state_crop(),
* v4l2_subdev_state_compose() and v4l2_subdev_state_get_interval() below.
*/
#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_ret(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 *
@ -1379,9 +1394,10 @@ __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_ret(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 *
@ -1400,9 +1416,10 @@ __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_ret(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 *
@ -1421,9 +1438,10 @@ __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_ret(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 *