linux-kernel - Re: [PATCH] fbdev: Have CONFIG_FB

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Message-Id: <618ea004-6fd9-4f1c-836a-fbf66089a03b@app.fastmail.com>
Date: Mon, 06 May 2024 17:14:23 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Daniel Vetter" <daniel@...ll.ch>,
 "Florian Fainelli" <florian.fainelli@...adcom.com>
Cc: linux-kernel@...r.kernel.org, "Helge Deller" <deller@....de>,
 "Thomas Zimmermann" <tzimmermann@...e.de>,
 "Javier Martinez Canillas" <javierm@...hat.com>,
 "Sam Ravnborg" <sam@...nborg.org>,
 "open list:FRAMEBUFFER LAYER" <linux-fbdev@...r.kernel.org>,
 "open list:FRAMEBUFFER LAYER" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] fbdev: Have CONFIG_FB_NOTIFY be tristate

On Mon, May 6, 2024, at 16:53, Arnd Bergmann wrote:
> On Mon, May 6, 2024, at 15:14, Daniel Vetter wrote:
>>
>> This one is. And it doesn't need to be simpledrm, just a drm kms driver
>> with fbdev emulation. Heck even if you have an fbdev driver you should
>> control the corresponding backlight explicitly, and not rely on the fb
>> notifier to magical enable/disable some random backlights somewhere.
>>
>> So please do not encourage using this in any modern code.
..
> Alternatively, I wonder if that recovery image could be changed
> to access the screen through the /dev/dri/ interfaces? I have
> no experience in using those without Xorg or Wayland, is that
> a sensible thing to do?

Replying to myself here, I think I found the answer in
https://android.googlesource.com/platform/bootable/recovery/+/refs/heads/main/minui/

which has separate backends for fbdev and drm, and should
just work as long as the drm driver is loaded in the
recovery image.

Florian, do you know why this is not being used on the
machines you are looking at?

      Arnd