linux-kernel - Re: [PATCH v2 3/3] efi: earlycon: Add support for generic framebuffers and move to console subsystem

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Date:   Wed, 07 Sep 2022 10:22:03 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Daniel Vetter" <daniel@...ll.ch>,
        "Markuss Broks" <markuss.broks@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        "Jonathan Corbet" <corbet@....net>,
        "Ard Biesheuvel" <ardb@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Jiri Slaby" <jirislaby@...nel.org>,
        "Helge Deller" <deller@....de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Borislav Petkov" <bp@...e.de>,
        "Kees Cook" <keescook@...omium.org>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        "Randy Dunlap" <rdunlap@...radead.org>,
        "Damien Le Moal" <damien.lemoal@...nsource.wdc.com>,
        "Thomas Zimmermann" <tzimmermann@...e.de>,
        "Michal Suchanek" <msuchanek@...e.de>,
        "Javier Martinez Canillas" <javierm@...hat.com>,
        "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
        "Wei Ming Chen" <jj251510319013@...il.com>,
        "Bartlomiej Zolnierkiewicz" <b.zolnierkie@...sung.com>,
        "Tony Lindgren" <tony@...mide.com>, linux-doc@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 3/3] efi: earlycon: Add support for generic framebuffers and
 move to console subsystem

On Tue, Sep 6, 2022, at 11:52 PM, Daniel Vetter wrote:
> On Sat, Aug 06, 2022 at 07:32:24PM +0300, Markuss Broks wrote:
>
> Ok I have a more fundamental issue with this than the lack of proper patch
> splitting I mentioned in the other thread.
>
> This is the wrong place.
>
> drivers/video/console is about the various vt console implementations,
> which supply a struct consw to con_register_driver.

You are right, that was my mistake. The original patch was for
drivers/video/fbdev/, and I suggested moving it out of there because
it does not depend on the fbdev subsystem, but clearly my suggestions
of drivers/video/console was equally wrong.

> This otoh is an (early) kernel/printk console implemented using struct
> console. Totally different thing, and really shouldn't end up in
> drivers/video/console imo. Somewhere in drivers/firmware might still be
> the best place, the sysfb stuff is also there. Maybe
> drivers/firmware/sysfb_earlycon.c?

drivers/firmware/ is better but doesn't sound great to me either,
since one important thing the patch does is to not make it depend
on EFI firmware or BIOS style screen_info any more. 

Maybe drivers/tty/earlycon_simplefb.c would work better, keeping
it close to the earlycon base support in drivers/tty/serial/,
the vt console and the old simplefb driver/, without tying to too
closely to fbdev of UEFI.

     Arnd