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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 24 Jan 2022 16:50:19 +0100
Message-ID: <CAMuHMdW-txqH1fnpkvyOSYUVkG8PTJKWkWFq_X8k-4VcdKR79Q@mail.gmail.com>
Subject: Re: [PATCH 2/2] Revert "fbcon: Disable accelerated scrolling"
To:     Helge Deller <deller@gmx.de>
Cc:     Javier Martinez Canillas <javierm@redhat.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
        Pavel Machek <pavel@ucw.cz>, Sam Ravnborg <sam@ravnborg.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sven Schnelle <svens@stackframe.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Claudio Suarez <cssk@net-c.es>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
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Hi Helge,

On Mon, Jan 24, 2022 at 4:30 PM Helge Deller <deller@gmx.de> wrote:
> On 1/24/22 12:50, Javier Martinez Canillas wrote:
> > On 1/24/22 12:33, Thomas Zimmermann wrote:
> >
> > [snip]
> >
> >>> Thoughts?
> >>
> >> I can't say I approve keeping fbdev alive, but...
> >>
> >> With fbdev emulation, every DRM driver is an fbdev driver too. So
> >> CONFIG_FB_DRIVER is somewhat misleading. Better add an option like
> >> CONFIG_FBCON_HW_SCROLLING and have it selected by the fbdev drivers that
> >> absolutely need HW acceleration. That option would then protect the rsp
> >> code.
>
> I'm not a fan of something like CONFIG_FBCON_HW_SCROLLING, but I'm not
> against it either.
> For me it sounds that this is not the real direction you want to go,
> which is to prevent that any other drivers take the framebuffer before
> you take it with simpledrm or similiar.
> CONFIG_FBCON_HW_SCROLLING IMHO just disables the (from your POV) neglectable accleration part.
> With an option like CONFIG_FB_DRIVER (maybe better: CONFIG_FB_LEGACY_DRIVERS)
> it's an easy option for distros to disable all of the legacy drivers
> from being built & shipped.
>
> Instead of CONFIG_FBCON_HW_SCROLLING we could also choose
> CONFIG_FBCON_LEGACY_ACCELERATION, because it includes fillrect() as well...

As this is about resurrecting features indicated by the various
FBINFO_HWACCEL_* flags, what about CONFIG_FB_HWACCEL?

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