linux-kernel - Re: [PATCH v3 4/6] drm/atomic: Avoid unused-but-set-variable warning on for_each_old_plane_in

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Date:   Wed, 9 Dec 2020 01:44:15 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Liu Ying <victor.liu@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, p.zabel@...gutronix.de,
        airlied@...ux.ie, daniel@...ll.ch, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, robh+dt@...nel.org,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, laurentiu.palcu@....nxp.com
Subject: Re: [PATCH v3 4/6] drm/atomic: Avoid unused-but-set-variable warning
 on for_each_old_plane_in_state

On Mon, Dec 07, 2020 at 11:20:58AM +0800, Liu Ying wrote:
> Artifically use 'plane' and 'old_plane_state' to avoid 'not used' warning.
> The precedent has already been set by other macros in the same file.
> 
> Signed-off-by: Liu Ying <victor.liu@....com>

Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>

I'm assuming someone will push this to drm-misc or some other tree. Should
probably land sooner than later.
-Daniel

> ---
> v2->v3:
> * Add a missing blank line.
> 
> v1->v2:
> * No change.
> 
>  include/drm/drm_atomic.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 54e051a..2e087d7 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -888,7 +888,10 @@ void drm_state_dump(struct drm_device *dev, struct drm_printer *p);
>  	     (__i)++)							\
>  		for_each_if ((__state)->planes[__i].ptr &&		\
>  			     ((plane) = (__state)->planes[__i].ptr,	\
> -			      (old_plane_state) = (__state)->planes[__i].old_state, 1))
> +			      (void)(plane) /* Only to avoid unused-but-set-variable warning */, \
> +			      (old_plane_state) = (__state)->planes[__i].old_state, \
> +			      (void)(old_plane_state) /* Only to avoid unused-but-set-variable warning */, 1))
> +
>  /**
>   * for_each_new_plane_in_state - iterate over all planes in an atomic update
>   * @__state: &struct drm_atomic_state pointer
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch