From patchwork Wed May 8 21:40:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Pinchart X-Patchwork-Id: 13659187 X-Patchwork-Delegate: kieran@bingham.xyz Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B452813248B; Wed, 8 May 2024 21:40:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715204462; cv=none; b=kVkcR5YvJ3UYo57OmiXgC7iRZ5AigHWhY5MhAGQ9L4E3Lef+bRsNwd3fcfFnmJoBAP0Y53Ro4JQW/iuJNmxyZ3XvSG9mu3Fnc6y7P5C9MLaCnGtC5PH6FuSnE0UWucm1aXXdDGGFBGMnXjJqO2AN2e3xv1TwSxGHpds+PxHdGDw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715204462; c=relaxed/simple; bh=kRYOBfB3Skh5PpdSwvI6oBAoy/LqssM5t1B1xt8dPlA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jyOX5hudOtFAz8k+OO23qpGrPgbSe02h3eVkNcN1qnmtodr1L0e3U+D2HO+0XuzoK75v4kb629rqZGaLUs+oQydLCzM8cCkkquiuh+g2SCZmLnrlkc+yXlnUNgtgJ6UzJVXEUNSgQVir1M0d7M86mdynz1Rif4hPOFf1Ig5Yh3g= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=YeZD99iA; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="YeZD99iA" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 0BA2A2CC7; Wed, 8 May 2024 23:40:53 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1715204454; bh=kRYOBfB3Skh5PpdSwvI6oBAoy/LqssM5t1B1xt8dPlA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YeZD99iAM6EifyVruYgs8/eR+mXchCMIkmHhAe6cN7e7v1EJ7ruUxstqW7Cx2RMbN aPJhidVPo1FiKkmmCk6nBiIHiV4pLHTyRnLSWarFJOLw6S2LL1ibcVCakEUNC+XCPY o+906xzTgMjJKh0Fdb1hkSRXDFU+/otUh8eaHGKY= From: Laurent Pinchart To: linux-media@vger.kernel.org Cc: linux-renesas-soc@vger.kernel.org, Sakari Ailus , Tomi Valkeinen , Hans Verkuil , Dafna Hirschfeld , linux-rockchip@lists.infradead.org Subject: [PATCH v4 2/3] media: v4l2-subdev: Provide const-aware subdev state accessors Date: Thu, 9 May 2024 00:40:44 +0300 Message-ID: <20240508214045.24716-3-laurent.pinchart+renesas@ideasonboard.com> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240508214045.24716-1-laurent.pinchart+renesas@ideasonboard.com> References: <20240508214045.24716-1-laurent.pinchart+renesas@ideasonboard.com> Precedence: bulk X-Mailing-List: linux-renesas-soc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 Reviewed-by: Sakari Ailus Reviewed-by: Tomi Valkeinen --- Changes since v3: - Rename __v4l2_subdev_state_constify_call() to __v4l2_subdev_state_constify_ret() - Update documentation 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 | 48 +++++++++++++++++++++++++------------ 1 file changed, 33 insertions(+), 15 deletions(-) diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h index b25b6e97ecbd..e1a6c49a966d 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_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 @@ -1343,13 +1353,18 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd); * 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 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 * @@ -1368,9 +1383,10 @@ __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 * @@ -1389,9 +1405,10 @@ __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 * @@ -1410,9 +1427,10 @@ __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 *