Re: [PATCH] drm/i915/tv: avoid possible division by zero

[Su Hui]

On 2023/7/18 13:39, Dan Carpenter wrote:
> On Mon, Jul 17, 2023 at 04:52:51PM +0200, Andrzej Hajda wrote:
> > On 17.07.2023 08:22, Su Hui wrote:
> > > Clang warning: drivers/gpu/drm/i915/display/intel_tv.c:
> > > line 991, column 22 Division by zero.
> > > Assuming tv_mode->oversample=1 and (!tv_mode->progressive)=1,
> > > then division by zero will happen.
> > >
> > > Fixes: 1bba5543e4fe ("drm/i915: Fix TV encoder clock computation")
> > > Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/i915/display/intel_tv.c | 3 ++-
> > >    1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_tv.c b/drivers/gpu/drm/i915/display/intel_tv.c
> > > index 36b479b46b60..82b54af51f23 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_tv.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_tv.c
> > > @@ -988,7 +988,8 @@ intel_tv_mode_to_mode(struct drm_display_mode *mode,
> > >    		      const struct tv_mode *tv_mode,
> > >    		      int clock)
> > >    {
> > > -	mode->clock = clock / (tv_mode->oversample >> !tv_mode->progressive);
> > > +	mode->clock = clock / (tv_mode->oversample != 1 ?
> > > +			tv_mode->oversample >> !tv_mode->progressive : 1);
> > Seems too smart to me, why not just:
> > mode->clock = clock / tv_mode->oversample;
> > if (!tv_mode->progressive)
> >      mode->clock <<= 1;
> This is nice.

mode->clock = clock / tv_mode->oversample << !tv_mode->progressive;

But I think this one is much better,  it has less code and run faster.
Should I resend v3 to add some explanation or follow Dan's advice?

Su Hui

> regards,
> dan carpenter