linux-kernel - Re: [PATCH] drm: xlnx: zynqmp_disp: Fix WARN

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Date: Wed, 22 May 2024 18:46:12 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Palmer Dabbelt <palmer@...osinc.com>
Cc: tomi.valkeinen@...asonboard.com, maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
	daniel@...ll.ch, michal.simek@....com,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel test robot <lkp@...el.com>,
	Anatoliy Klymenko <anatoliy.klymenko@....com>
Subject: Re: [PATCH] drm: xlnx: zynqmp_disp: Fix WARN_ON build warning

On Wed, May 22, 2024 at 06:45:29PM +0300, Laurent Pinchart wrote:
> On Wed, May 22, 2024 at 05:44:02PM +0300, Laurent Pinchart wrote:
> > 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@...osinc.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@...el.com>
> > > Closes: https://lore.kernel.org/oe-kbuild-all/202405080553.tfH9EmS8-lkp@intel.com/
> > > Signed-off-by: Palmer Dabbelt <palmer@...osinc.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 ?
> 
> I see a fix is already present in the drm-misc-fixes branch. Please
> ignore my previous e-mail.

I meant drm-misc-next-fixes.

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

-- 
Regards,

Laurent Pinchart