linux-kernel - Re: [PATCH linux-next] drm/i915/display: Remove the useless variable offset and its assignment

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Message-ID: <87y24v4hgu.fsf@intel.com>
Date:   Wed, 08 Dec 2021 10:40:49 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     cgel.zte@...il.com
Cc:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, luo penghao <luo.penghao@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH linux-next] drm/i915/display: Remove the useless
 variable offset and its assignment

On Wed, 08 Dec 2021, cgel.zte@...il.com wrote:
> From: luo penghao <luo.penghao@....com.cn>
>
> The existence of offset is meaningless, so it should be deleted.
>
> The clang_analyzer complains as follows:
>
> Value stored to 'offset' is never read
>
> Reported-by: Zeal Robot <zealci@....com.cn>
> Signed-off-by: luo penghao <luo.penghao@....com.cn>

I've said the same things before, and I'll say them again.

Having an unused variable like this could be an indication of a bug
introduced by an earlier change; maybe we should still be using the
variable but no longer do. Please figure out when the variable became
unused and reference the commit so we can tell.

If cgel.zte@...il.com sends the patches, we'll need their name and
Signed-off-by too.

Thanks for the report, but I'll consider this as a report only.


BR,
Jani.


> ---
>  drivers/gpu/drm/i915/display/i9xx_plane.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/i9xx_plane.c b/drivers/gpu/drm/i915/display/i9xx_plane.c
> index b1439ba..a478b7f 100644
> --- a/drivers/gpu/drm/i915/display/i9xx_plane.c
> +++ b/drivers/gpu/drm/i915/display/i9xx_plane.c
> @@ -964,7 +964,7 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
>  	struct intel_plane *plane = to_intel_plane(crtc->base.primary);
>  	enum i9xx_plane_id i9xx_plane = plane->i9xx_plane;
>  	enum pipe pipe;
> -	u32 val, base, offset;
> +	u32 val, base;
>  	int fourcc, pixel_format;
>  	unsigned int aligned_height;
>  	struct drm_framebuffer *fb;
> @@ -1006,14 +1006,14 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
>  	fb->format = drm_format_info(fourcc);
>  
>  	if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
> -		offset = intel_de_read(dev_priv, DSPOFFSET(i9xx_plane));
> +		intel_de_read(dev_priv, DSPOFFSET(i9xx_plane));
>  		base = intel_de_read(dev_priv, DSPSURF(i9xx_plane)) & 0xfffff000;
>  	} else if (DISPLAY_VER(dev_priv) >= 4) {
>  		if (plane_config->tiling)
> -			offset = intel_de_read(dev_priv,
> +			intel_de_read(dev_priv,
>  					       DSPTILEOFF(i9xx_plane));
>  		else
> -			offset = intel_de_read(dev_priv,
> +			intel_de_read(dev_priv,
>  					       DSPLINOFF(i9xx_plane));
>  		base = intel_de_read(dev_priv, DSPSURF(i9xx_plane)) & 0xfffff000;
>  	} else {

-- 
Jani Nikula, Intel Open Source Graphics Center