[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 at nfschina.com>
>>> ---
>>>    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