linux-kernel - Re: [PATCH 02/29] drm/atomic: Fix unused but set warning in for_each_old_plane_in

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Message-ID: <20250902192544.GQ13448@pendragon.ideasonboard.com>
Date: Tue, 2 Sep 2025 21:25:44 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Jyri Sarha <jyri.sarha@....fi>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Devarsh Thakkar <devarsht@...com>, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/29] drm/atomic: Fix unused but set warning in
 for_each_old_plane_in_state

Hi Maxime,

Thank you for the patch.

On Tue, Sep 02, 2025 at 10:32:30AM +0200, Maxime Ripard wrote:
> The for_each_old_plane_in_state() macro triggers a compiler warning if
> the plane parameter passed to it isn't used in the code block.
> 
> Add a similar workaround than in most other macros.
> 
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>  include/drm/drm_atomic.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 38636a593c9d98cadda85ccd67326cb152f0dd27..689a29bdeb4a06672ab6fffecb513d58ff6e07f9 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -1053,11 +1053,13 @@ void drm_state_dump(struct drm_device *dev, struct drm_printer *p);
>  	for ((__i) = 0;							\
>  	     (__i) < (__state)->dev->mode_config.num_total_plane;	\
>  	     (__i)++)							\
>  		for_each_if ((__state)->planes[__i].ptr &&		\
>  			     ((plane) = (__state)->planes[__i].ptr,	\
> +			      (void)(plane) /* Only to avoid unused-but-set-variable warning */, \
>  			      (old_plane_state) = (__state)->planes[__i].old_state, 1))
> +

While at it, shouldn't you apply the same workaround to the
old_plane_state variable, like done for new_plane_state in
for_each_new_plane_in_state() ? Or is it expected that drivers will
always make use of it.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

>  /**
>   * for_each_new_plane_in_state - iterate over all planes in an atomic update
>   * @__state: &struct drm_atomic_state pointer
>   * @plane: &struct drm_plane iteration cursor
>   * @new_plane_state: &struct drm_plane_state iteration cursor for the new state

-- 
Regards,

Laurent Pinchart