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Tue, 21 Oct 2025 00:42:54 -0700 (PDT) Message-ID: Date: Tue, 21 Oct 2025 09:42:46 +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> Content-Language: en-US From: Mehdi Ben Hadj Khelifa In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/21/25 7:57 AM, Thomas Zimmermann wrote: > > > Am 21.10.25 um 08:51 schrieb Thomas Zimmermann: >> 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. >> >> Best regards >> 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); > > And TBH I'm not sure if we should really convert this call. It's not an > array in the sense of that API. > > Good candidates look like 'kmalloc(count * sizeof( variable>))' > I will leave kmalloc in v3. Do you want me to send deep testing information on this patch? BR, Mehdi>>>       if (!buf) { >>>           ret = -ENOMEM; >>>           goto out_exit; >> >