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Tue, 21 Oct 2025 01:44:21 -0700 (PDT) Message-ID: Date: Tue, 21 Oct 2025 10:44:12 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/tiny: Refactor framebuffer's size calculation To: Thomas Zimmermann , lanzano.alex@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, khalid@kernel.org, linux-kernel-mentees@lists.linuxfoundation.org References: <20251020115803.192572-1-mehdi.benhadjkhelifa@gmail.com> <1de3112b-6349-46d8-b90b-69d0849c7659@suse.de> <6a917f07-18dd-4f8f-bfc5-b85d9051339d@gmail.com> <4b01c775-f87a-4c3c-88f1-f5c52261d9b2@suse.de> Content-Language: en-US From: Mehdi Ben Hadj Khelifa In-Reply-To: <4b01c775-f87a-4c3c-88f1-f5c52261d9b2@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/21/25 9:32 AM, Thomas Zimmermann wrote: > Hi > > Am 21.10.25 um 10:41 schrieb Mehdi Ben Hadj Khelifa: >> On 10/21/25 7:51 AM, Thomas Zimmermann wrote: >>> Hi >>> >>> Am 20.10.25 um 13:57 schrieb Mehdi Ben Hadj Khelifa: >>>> Use drm_format_info_min_pitch() to calculate the framebuffer line pitch >>>> instead of directly multiplying width and height. This aligns with DRM >>>> helpers for determining per-line byte size and avoids manual >>>> assumptions >>>> about bytes per pixel. >>>> >>>> Suggested-by: Thomas Zimmermann >>>> Signed-off-by: Mehdi Ben Hadj Khelifa >>>> --- >>>>   drivers/gpu/drm/tiny/repaper.c | 6 +++++- >>>>   1 file changed, 5 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/gpu/drm/tiny/repaper.c b/drivers/gpu/drm/tiny/ >>>> repaper.c >>>> index 4824f863fdba..aeff49bc6ba7 100644 >>>> --- a/drivers/gpu/drm/tiny/repaper.c >>>> +++ b/drivers/gpu/drm/tiny/repaper.c >>>> @@ -517,6 +517,8 @@ static int repaper_fb_dirty(struct >>>> drm_framebuffer *fb, const struct iosys_map * >>>>       unsigned int dst_pitch = 0; >>>>       struct iosys_map dst; >>>>       struct drm_rect clip; >>>> +    const struct drm_format_info *info = fb->format; >>> >>> This is the wrong format. You're allocating the output buffer here, >>> but you're using the input format. IIUC the output format is >>> DRM_FORMAT_R1. The input is _XRGB8888. >>> >> Ah. Thanks for clarification.I thought since it had the same output >> format. I will send a v3 shortly.> Best regards > > Maybe just don't do it. This is just churn with no clear goal. > Okay,I will abort working on it.Though my goal was to remove the manual assumption that height is multiple of 8 and to align with other 'correct' API used in other drm drivers as you suggested[1]. [1]:https://lore.kernel.org/all/cb0f0a36-0593-4d4c-8450-d086b9c99d87@suse.de/ Best Regards, Mehdi Ben Hadj Khelifa> Best regards > Thomas > >>> Thomas >>> >>>> +    size_t pitch; >>>>       int idx, ret = 0; >>>>       u8 *buf = NULL; >>>> @@ -534,7 +536,9 @@ static int repaper_fb_dirty(struct >>>> drm_framebuffer *fb, const struct iosys_map * >>>>       DRM_DEBUG("Flushing [FB:%d] st=%ums\n", fb->base.id, >>>>             epd->factored_stage_time); >>>> -    buf = kmalloc(fb->width * fb->height / 8, GFP_KERNEL); >>>> +    pitch = drm_format_info_min_pitch(info, 0, fb->width); >>>> + >>>> +    buf = kmalloc_array(fb->height, pitch, GFP_KERNEL); >>>>       if (!buf) { >>>>           ret = -ENOMEM; >>>>           goto out_exit; >>> >> >