Re: [PATCH] drm: xlnx: zynqmp_disp: Fix WARN_ON build warning

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Palmer Dabbelt <palmer@rivosinc.com>
Cc: tomi.valkeinen@ideasonboard.com,
	maarten.lankhorst@linux.intel.com, mripard@kernel.org,
	tzimmermann@suse.de, airlied@gmail.com, daniel@ffwll.ch,
	michal.simek@amd.com, dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, kernel test robot <lkp@intel.com>,
	Anatoliy Klymenko <anatoliy.klymenko@amd.com>
Subject: Re: [PATCH] drm: xlnx: zynqmp_disp: Fix WARN_ON build warning
Date: Wed, 22 May 2024 17:44:01 +0300	[thread overview]
Message-ID: <20240522144401.GA9789@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20240521142814.32145-2-palmer@rivosinc.com>

Hi Palmer,

(CC'ing Anatoliy)

Thank you for the patch.

On Tue, May 21, 2024 at 07:28:15AM -0700, Palmer Dabbelt wrote:
> From: Palmer Dabbelt <palmer@rivosinc.com>
> 
> Without this I get warnings along the lines of
> 
>     drivers/gpu/drm/xlnx/zynqmp_disp.c:949:14: error: logical not is only applied to the left hand side of this comparison [-Werror,-Wlogical-not-parentheses]
>       949 |         if (WARN_ON(!layer->mode == ZYNQMP_DPSUB_LAYER_NONLIVE)) {
>           |                     ^            ~~
>     arch/s390/include/asm/bug.h:54:25: note: expanded from macro 'WARN_ON'
>        54 |         int __ret_warn_on = !!(x);                      \
>           |                                ^
>     drivers/gpu/drm/xlnx/zynqmp_disp.c:949:14: note: add parentheses after the '!' to evaluate the comparison first
>     drivers/gpu/drm/xlnx/zynqmp_disp.c:949:14: note: add parentheses around left hand side expression to silence this warning
> 
> which get promoted to errors in my test builds.  Adding the suggested
> parens elides those warnings.

I think this should have

Fixes: b0f0469ab662 ("drm: xlnx: zynqmp_dpsub: Anounce supported input formats")

> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202405080553.tfH9EmS8-lkp@intel.com/
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
> I couldn't find a patch for this in Linus' tree or on the lists, sorry
> if someone's already fixed it.  No rush on my end, I'll just stash this
> in a local branch for the tester.
> ---
>  drivers/gpu/drm/xlnx/zynqmp_disp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> index 13157da0089e..d37b4a9c99ea 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> @@ -981,7 +981,7 @@ u32 *zynqmp_disp_layer_drm_formats(struct zynqmp_disp_layer *layer,
>  	unsigned int i;
>  	u32 *formats;
>  
> -	if (WARN_ON(!layer->mode == ZYNQMP_DPSUB_LAYER_NONLIVE)) {
> +	if (WARN_ON((!layer->mode) == ZYNQMP_DPSUB_LAYER_NONLIVE)) {

That doesn't seem right. layer->mode isn't a boolean, it's an enum. The
right fix seems to be

	if (WARN_ON(layer->mode != ZYNQMP_DPSUB_LAYER_NONLIVE)) {

Anatoliy, could you check this ? Palmer, do you plan to submit a new
version of the patch, or should I send the right fix separately ?

>  		*num_formats = 0;
>  		return NULL;
>  	}

-- 
Regards,

Laurent Pinchart

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