linux-kernel - Re: [RFC PATCH 0/3] staging: remove fbdev drivers

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Message-ID: <1481232877.26959.52.camel@kernel.crashing.org>
Date:   Fri, 09 Dec 2016 08:34:37 +1100
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Daniel Vetter <daniel@...ll.ch>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Teddy Wang <teddy.wang@...iconmotion.com>,
        Arnaud Patard <arnaud.patard@...-net.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers

On Thu, 2016-12-08 at 16:21 +0100, Daniel Vetter wrote:
> Yeah, small drivers like these we have piles now, things exploded a lot
> after atomic landed two years ago. And they seem to shrink with every
> release a bit more (since lots more drivers gives you lots more insight
> into what other refactorings would make sense). Those we have a big pile
> of, and nowadays (at least with developers expirienced with upstream, but
> not necessarily with drm) it takes but a few weeks from initial submission
> to getting them merged.
> 
> What we don't yet have a nice tidy example driver of is the even simpler
> "dumb framebuffer behind a slow bus with explicit/manual upload", for like
> small i2c/spi panels (and conceptually also usb, even though there bw and
> panel size are a bit scaled up). We've gained some really nice helpers for
> this this year, and there's 3 drivers in-flight to make use of it. But
> since that's right now just a hobbyist effort it's moving a bit slower
> (and I was mistaken a few weeks back where I assumed that one of them
> landed already).

What I find usually confusing is the interaction with the TTM and
overall fb memory management, when trying to plumb in simple 2d accel
to speed up fbcon mostly (but I don't mind making it available to user
space via ioctls, though that's not a priority).

As I mentioned earlier, probably 1 or 2 years ago, Dave made the
argument that shadowing through memory was necessary and precluded 2D
accel, though I don't fully remember the root of the argument. If that
is indeed not the case, then my main objection is lifted.

Cheers,
Ben.