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

[Klymenko, Anatoliy]

Hi Laurent and Palmer,

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Sent: Wednesday, May 22, 2024 7:44 AM
> To: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> Cc: tomi.valkeinen@xxxxxxxxxxxxxxxx;
> maarten.lankhorst@xxxxxxxxxxxxxxx; mripard@xxxxxxxxxx;
> tzimmermann@xxxxxxx; airlied@xxxxxxxxx; daniel@xxxxxxxx; Simek,
> Michal <michal.simek@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> kernel test robot <lkp@xxxxxxxxx>; Klymenko, Anatoliy
> <Anatoliy.Klymenko@xxxxxxx>
> Subject: Re: [PATCH] drm: xlnx: zynqmp_disp: Fix WARN_ON build
> warning
> 
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
> 
> 
> 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@xxxxxxxxxxxx>
> >
> > 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@xxxxxxxxx>
> > Closes: https://lore.kernel.org/oe-kbuild-all/202405080553.tfH9EmS8-
> lkp@xxxxxxxxx/
> > Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> > ---
> > 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)) {
> 

Yes, this is how it should be.

> 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 ?
> 

Actually, this has been fixed here:
https://cgit.freedesktop.org/drm/drm-misc/commit/?id=c72211751870ffa2cff5d91834059456cfa7cbd5.
Looks like the fix just missed the merge window.

> >               *num_formats = 0;
> >               return NULL;
> >       }
> 
> --
> Regards,
> 
> Laurent Pinchart
--
Thank you,
Anatoliy