Re: [PATCH] drm/fb-helper: Fix clipping when damage area spans a single scanline

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 30.04.26 um 17:35 schrieb Francesco Lavra:
> Friendly ping

Sorry, forgot this patch. It's merged now. Thanks a lot.

Best regards
Thomas

>
> On Tue, 2026-02-10 at 18:35 +0100, Francesco Lavra wrote:
>> When the damage area resulting from a dirty memory range spans a single
>> scanline, the width of the rectangle is calculated dynamically because it
>> may not coincide with the framebuffer width.
>> If the dirty range ends exactly at the end of the scanline, the `bit_end`
>> variable is incorrectly assigned a 0 value, which results in a bogus clip
>> rectangle where the x2 coordinate is 0. This prevents the dirty scanline
>> from being flushed to the hardware.
>> Change the calculation of the `bit_end` value to fix the x2 coordinate
>> value in the above edge case.
>>
>> Fixes: ded74cafeea9 ("drm/fb-helper: Clip damage area horizontally")
>> Signed-off-by: Francesco Lavra <flavra@baylibre.com>
>> ---
>>   drivers/gpu/drm/drm_fb_helper.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c
>> b/drivers/gpu/drm/drm_fb_helper.c
>> index 4b47aa0dab35..d545342d24b3 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -608,7 +608,7 @@ static void drm_fb_helper_memory_range_to_clip(struct
>> fb_info *info, off_t off,
>>                   * the number of horizontal pixels that need an update.
>>                   */
>>                  off_t bit_off = (off % line_length) * 8;
>> -               off_t bit_end = (end % line_length) * 8;
>> +               off_t bit_end = bit_off + len * 8;
>>   
>>                  x1 = bit_off / info->var.bits_per_pixel;
>>                  x2 = DIV_ROUND_UP(bit_end, info->var.bits_per_pixel);

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)