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

From: Lee Jones <lee.jones@linaro.org>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: Philipp Zabel <p.zabel@pengutronix.de>,
	David Airlie <airlied@linux.ie>,
	Fabio Estevam <festevam@gmail.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	NXP Linux Team <linux-imx@nxp.com>,
	Daniel Vetter <daniel@ffwll.ch>, Shawn Guo <shawnguo@kernel.org>,
	Pengutronix Kernel Team <kernel@pengutronix.de>
Subject: Re: [PATCH 03/19] gpu: drm: imx: ipuv3-plane: Mark 'crtc_state' as __always_unused
Date: Fri, 6 Nov 2020 08:49:04 +0000	[thread overview]
Message-ID: <20201106084904.GY4488@dell> (raw)
In-Reply-To: <5056c156-9f6c-8e0d-54e8-5317fdd46c12@pengutronix.de>

On Fri, 06 Nov 2020, Ahmad Fatoum wrote:

> On 11/6/20 8:41 AM, Lee Jones wrote:
> > 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.
> 
> How do you mean? I wonder if
> 
>  #define for_each_oldnew_crtc_in_state(__state, crtc, old_crtc_state, new_crtc_state, __i) \
>         for ((__i) = 0;                                                 \
>              (__i) < (__state)->dev->mode_config.num_crtc;              \
>              (__i)++)                                                   \
>                 for_each_if ((__state)->crtcs[__i].ptr &&               \
>                              ((crtc) = (__state)->crtcs[__i].ptr,       \
>                               (void)(crtc) /* Only to avoid unused-but-set-variable warning */, \
>                              (old_crtc_state) = (__state)->crtcs[__i].old_state, \
>                              (void)(old_crtc_state) /* Only to avoid unused-but-set-variable warning */, \
> -                            (new_crtc_state) = (__state)->crtcs[__i].new_state, 1))
> +                            (new_crtc_state) = (__state)->crtcs[__i].new_state, \
> +                            (void)(new_crtc_state), 1))
> 
> wouldn't be better.

That also works for me.  I can fix this up.

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