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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 24 Apr 2023 09:31:22 +0200
Message-ID: <CAMuHMdVGEeAsmb4tAuuqqGJ-4+BBETwEwYJA+M9NyJv0BJ_hNg@mail.gmail.com>
Subject: Re: [PATCH 1/2] fbdev/offb: Update expected device name
To:     Cyril Brulebois <cyril@debamax.com>
Cc:     linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Herring <robh@kernel.org>,
        Michal Suchanek <msuchanek@suse.de>,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>
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Hi Cyril,

CC DT

On Wed, Apr 12, 2023 at 12:05 PM Cyril Brulebois <cyril@debamax.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.
>
> It might be better to iterate on all possible nodes, but updating the
> hardcoded device from "of-display" to "of-display.0" is confirmed to fix
> the Debian Installer at the very least.
>
> 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@vger.kernel.org
> Signed-off-by: Cyril Brulebois <cyril@debamax.com>

Thanks for your patch, which is now commit 27c74ea74be805cc
("fbdev/offb: Update expected device name") in fbdev/for-next

> --- a/drivers/video/fbdev/offb.c
> +++ b/drivers/video/fbdev/offb.c
> @@ -698,7 +698,7 @@ MODULE_DEVICE_TABLE(of, offb_of_match_display);
>
>  static struct platform_driver offb_driver_display = {
>         .driver = {
> -               .name = "of-display",
> +               .name = "of-display.0",
>                 .of_match_table = offb_of_match_display,
>         },
>         .probe = offb_probe_display,

This looks like the wrong fix for me: platform drivers' names must
not contain the device index, and DT-based devices are probed using
the compatible value (which is "display") instead of the node name.

I think the problem is with the of_platform_default_populate_init()
function, which should create proper name@unit-address device nodes,
with unique unit addresses, and with the correct compatible value.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds