Re: [Intel-gfx] [PATCH v2] drm/i915/tv: avoid possible division by zero

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 2023/7/25 01:35, Andi Shyti wrote:
On Tue, Jul 18, 2023 at 09:32:17AM +0800, 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 | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_tv.c b/drivers/gpu/drm/i915/display/intel_tv.c
index 36b479b46b60..f59553f7c132 100644
--- a/drivers/gpu/drm/i915/display/intel_tv.c
+++ b/drivers/gpu/drm/i915/display/intel_tv.c
@@ -988,7 +988,7 @@ 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 << !tv_mode->progressive;
but this does not provide the same value. Try with:

	8 / (2 >> 1)

and

	8 / 2 << 1

They are definitely different.

The real check could be:

	if (!(tv_mode->oversample >> 1))
		return ...

But first I would check if that's actually possible.

Oh, I have a v3 patch, like this:

-       mode->clock = clock / (tv_mode->oversample >> !tv_mode->progressive);
+       mode->clock = clock;
+       if (tv_mode->oversample >> !tv_mode->progressive)
+               mode->clock /= tv_mode->oversample >> 1;

But I'm not sure does it need to print some error messages or do some things  when
"tv_mode->oversample << !tv_mode->progressive" is zero?
If all right , I will send this v3 patch.

Su Hui

Andi



[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux