Hi Laurent, Thanks for the update. This is starting to look very nice. A few comments below... 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@xxxxxxxxxxxxxxxx> > --- > 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? Either way, Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > + _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. > */ > -#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 * -- Kind regards, Sakari Ailus
