linux-kernel - Re: [PATCH 03/19] gpu: drm: imx: ipuv3-plane: Mark 'crtc_state' as __always

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Message-ID: <20201106074151.GU4488@dell>
Date:   Fri, 6 Nov 2020 07:41:51 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Fabio Estevam <festevam@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        NXP Linux Team <linux-imx@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [PATCH 03/19] gpu: drm: imx: ipuv3-plane: Mark 'crtc_state' as
 __always_unused

On Thu, 05 Nov 2020, Ahmad Fatoum wrote:

> Hello Lee,
> 
> On 11/5/20 3:45 PM, Lee Jones wrote:
> > In the macro for_each_oldnew_crtc_in_state() 'crtc_state' is provided
> > as a container for state->crtcs[i].new_state, but is not utilised in
> > this use-case.  We cannot simply delete the variable, so here we tell
> > the compiler that we're intentionally discarding the read value.
> 
> for_each_oldnew_crtc_in_state already (void) casts the drm_crtc and the old
> drm_crtc_state to silence unused-but-set-variable warning. Should we maybe
> (void) cast the new crtc_state as well?

>From what I saw, it only void casts the ones which aren't assigned.

> > Fixes the following W=1 kernel build warning(s):
> > 
> >  drivers/gpu/drm/imx/ipuv3-plane.c: In function ‘ipu_planes_assign_pre’:
> >  drivers/gpu/drm/imx/ipuv3-plane.c:746:42: warning: variable ‘crtc_state’ set but not used [-Wunused-but-set-variable]
> > 
> > Cc: Philipp Zabel <p.zabel@...gutronix.de>
> > Cc: David Airlie <airlied@...ux.ie>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Shawn Guo <shawnguo@...nel.org>
> > Cc: Sascha Hauer <s.hauer@...gutronix.de>
> > Cc: Pengutronix Kernel Team <kernel@...gutronix.de>
> > Cc: Fabio Estevam <festevam@...il.com>
> > Cc: NXP Linux Team <linux-imx@....com>
> > Cc: dri-devel@...ts.freedesktop.org
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  drivers/gpu/drm/imx/ipuv3-plane.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/imx/ipuv3-plane.c b/drivers/gpu/drm/imx/ipuv3-plane.c
> > index 8a4235d9d9f1e..acc0a3ce4992f 100644
> > --- a/drivers/gpu/drm/imx/ipuv3-plane.c
> > +++ b/drivers/gpu/drm/imx/ipuv3-plane.c
> > @@ -743,7 +743,7 @@ bool ipu_plane_atomic_update_pending(struct drm_plane *plane)
> >  int ipu_planes_assign_pre(struct drm_device *dev,
> >  			  struct drm_atomic_state *state)
> >  {
> > -	struct drm_crtc_state *old_crtc_state, *crtc_state;
> > +	struct drm_crtc_state *old_crtc_state, __always_unused *crtc_state;
> >  	struct drm_plane_state *plane_state;
> >  	struct ipu_plane_state *ipu_state;
> >  	struct ipu_plane *ipu_plane;
> > 
> 

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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