linux-kernel - Re: [PATCH] firmware/sysfb: Fix wrong stride when bits-per-pixel is calculated

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Message-ID: <87v8hueu0g.fsf@minerva.mail-host-address-is-not-set>
Date:   Mon, 17 Apr 2023 11:29:51 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        Pierre Asselin <pa@...ix.com>
Cc:     jfalempe@...hat.com, daniel.vetter@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        hdegoede@...hat.com, ardb@...nel.org
Subject: Re: [PATCH] firmware/sysfb: Fix wrong stride when bits-per-pixel is
 calculated

Thomas Zimmermann <tzimmermann@...e.de> writes:

[...]

>> 
>>     stride = DIV_ROUND_UP(si->lfb_width * bits_per_pixel, 8)
>
> I'd rather keep the code as-is until we get an actual bug report.
>

Ok. After all if the pixel format is chosen correctly, the reported line
length should match anyways. So is really a corner case what Pierre had.

> For example, DRM framebuffer sizes are often multiples of 64. Creating a 
> framebuffer of 800x600 will create a framebuffer with 
> stride/pitch/linelength of 832.  I can imagine that some BIOSes out 
> there do something similar with the system framebuffer. Messing with the 
> stride would break them.
>

I see, is not that simple then. Thanks a lot for the clarification.

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat