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

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Date:   Mon, 24 Apr 2023 11:35:41 +0200
From:   Helge Deller <deller@....de>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        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

On 4/24/23 11:07, Thomas Zimmermann wrote:
> 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.

Geert & Thomas, thanks for the review!

I've dropped both patches from fbdev tree for now.
Would be great to find another good solution though, as it breaks the debian
installer.

Helge