linux-kernel - Re: [PATCH 2/2] drm/ofdrm: Update expected device name

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Date:   Mon, 24 Apr 2023 11:07:45 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Cyril Brulebois <cyril@...amax.com>
Cc:     linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Rob Herring <robh@...nel.org>,
        Michal Suchanek <msuchanek@...e.de>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/ofdrm: Update expected device name

Hi

Am 24.04.23 um 09:33 schrieb Geert Uytterhoeven:
> Hi Cyril,
> 
> CC DT
> 
> On Wed, Apr 12, 2023 at 12:05 PM Cyril Brulebois <cyril@...amax.com> wrote:
>> Since commit 241d2fb56a18 ("of: Make OF framebuffer device names unique"),
>> as spotted by Frédéric Bonnard, the historical "of-display" device is
>> gone: the updated logic creates "of-display.0" instead, then as many
>> "of-display.N" as required.
>>
>> This means that offb no longer finds the expected device, which prevents
>> the Debian Installer from setting up its interface, at least on ppc64el.
>>
>> Given the code similarity it is likely to affect ofdrm in the same way.
>>
>> It might be better to iterate on all possible nodes, but updating the
>> hardcoded device from "of-display" to "of-display.0" is likely to help
>> as a first step.
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217328
>> Link: https://bugs.debian.org/1033058
>> Fixes: 241d2fb56a18 ("of: Make OF framebuffer device names unique")
>> Cc: stable@...r.kernel.org # v6.2+
>> Signed-off-by: Cyril Brulebois <cyril@...amax.com>
> 
> Thanks for your patch, which is now commit 3a9d8ea2539ebebd
> ("drm/ofdrm: Update expected device name") in fbdev/for-next.
> 
>> --- a/drivers/gpu/drm/tiny/ofdrm.c
>> +++ b/drivers/gpu/drm/tiny/ofdrm.c
>> @@ -1390,7 +1390,7 @@ MODULE_DEVICE_TABLE(of, ofdrm_of_match_display);
>>
>>   static struct platform_driver ofdrm_platform_driver = {
>>          .driver = {
>> -               .name = "of-display",
>> +               .name = "of-display.0",
>>                  .of_match_table = ofdrm_of_match_display,
>>          },
>>          .probe = ofdrm_probe,
> 
> Same comment as for "[PATCH 1/2] fbdev/offb: Update expected device
> name".
> 
> https://lore.kernel.org/r/CAMuHMdVGEeAsmb4tAuuqqGJ-4+BBETwEwYJA+M9NyJv0BJ_hNg@mail.gmail.com

Sorry that I missed this patch. I agree that it's probably not correct. 
At least in ofdrm, we want to be able to use multiple framebuffers at 
the same time; a feature that has been broken by this change.

Best regards
Thomas

> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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