From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
To: linux-media@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org,
Sakari Ailus <sakari.ailus@iki.fi>,
Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Dafna Hirschfeld <dafna@fastmail.com>,
linux-rockchip@lists.infradead.org
Subject: [PATCH v3 1/2] media: v4l2-subdev: Provide const-aware subdev state accessors
Date: Tue, 7 May 2024 19:19:06 +0300 [thread overview]
Message-ID: <20240507161907.27747-2-laurent.pinchart+renesas@ideasonboard.com> (raw)
In-Reply-To: <20240507161907.27747-1-laurent.pinchart+renesas@ideasonboard.com>
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) \
+ _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.
*/
-#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:[~2024-05-07 16:19 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 ` Laurent Pinchart [this message]
2024-05-08 18:44 ` [PATCH v3 1/2] media: v4l2-subdev: Provide const-aware subdev " Sakari Ailus
2024-05-08 18:48 ` Tomi Valkeinen
2024-05-08 21:02 ` Laurent Pinchart
2024-05-07 16:19 ` [PATCH v3 2/2] media: rkisp1: Mark subdev state pointers as const Laurent Pinchart
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