linux-kernel - Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

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Message-ID: <CAHp75VfxQMTMMSZvNBtHGGQAyBaURrBTddtuiQqFmpcjWG6Ktg@mail.gmail.com>
Date:   Tue, 26 Jun 2018 20:12:20 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

On Tue, Jun 26, 2018 at 4:55 PM, Hans de Goede <hdegoede@...hat.com> wrote:
> Currently fbcon claims fbdevs as soon as they are registered and takes over
> the console as soon as the first fbdev gets registered.
>
> This behavior is undesirable in cases where a smooth graphical bootup is
> desired, in such cases we typically want the contents of the framebuffer
> (typically a vendor logo) to stay in place as is.
>
> The current solution for this problem (on embedded systems) is to not
> enable fbcon.
>
> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
> which when enabled defers fbcon taking over the console from the dummy
> console until the first text is displayed on the console. Together with the
> "quiet" kernel commandline option, this allows fbcon to still be used
> together with a smooth graphical bootup, having it take over the console as
> soon as e.g. an error message is logged.

> +       for (i = 0; i < FB_MAX; i++) {
> +               if (registered_fb[i])
> +                       fbcon_fb_registered(registered_fb[i]);
> +       }

Simple git grep shows that we perhaps do

#define for_each_registered_fbcon(i) ...

(As an example see for_each_pci_bridge() how it's done there)

-- 
With Best Regards,
Andy Shevchenko