linux-kernel - Re: Is it possible to reset graphics controller on reboot in a framebuffer driver?

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Message-ID: <20190307213759.GA14798@localhost.localdomain>
Date:   Fri, 8 Mar 2019 05:38:00 +0800
From:   Tom Li <tomli@...li.me>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Yifeng Li <tomli@...li.me>,
        Teddy Wang <teddy.wang@...iconmotion.com>
Subject: Re: Is it possible to reset graphics controller on reboot in a
 framebuffer driver?

On Thu, Mar 07, 2019 at 10:39:23AM +0100, Geert Uytterhoeven wrote:
> On Thu, Mar 7, 2019 at 10:00 AM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
> > It's possible to do this using a reboot notifier. I am not sure if there
> > are better ways to achieve the same, but there's at least one example of
> > using reboot notifiers to achieve the exact same goal.
> >
> > See drivers/video/fbdev/aty/atyfb_base.c, look for
> > register_reboot_notifier().
> 
> Or a shutdown handler, which is more device-centric?
> (cfr. "[3/4] fbdev: atafb: Fix broken frame buffer after kexec",
>  https://patchwork.kernel.org/patch/10814381/).
> 
> Gr{oetje,eeting}s,

Thanks, I knew reboot_notifier but I thought it feels "hacky" to use it in a
device driver, shutdown() handler looks better.

Nevertheless, does it mean there's no way to prevent it from happening if the
user issues a emergency reboot? Like an automatic reboot after a kernel panic,
or a SysRq-B reboot.

Tom Li