Message-ID: <CAKMK7uEDcTTURyL6=VOJdjrVh7CszL_AqGogzHjfQqdDMMCr=g@mail.gmail.com>
Date:   Mon, 17 Jan 2022 16:56:11 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Helge Deller <deller@....de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "airlied@...il.com" <airlied@...il.com>,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] MAINTAINERS: Add Helge as fbdev maintainer

On Mon, Jan 17, 2022 at 4:43 PM Helge Deller <deller@....de> wrote:
>
> On 1/17/22 16:00, Daniel Vetter wrote:
> > On Mon, Jan 17, 2022 at 1:16 PM Helge Deller <deller@....de> wrote:
> >>
> >> Hello Daniel,
> >>
> >> On 1/17/22 11:02, Daniel Vetter wrote:
> >>> Hi Helge
> >>>
> >>> On Fri, Jan 14, 2022 at 7:18 PM Helge Deller <deller@....de> wrote:
> >>>>
> >>>> The fbdev layer is orphaned, but seems to need some care.
> >>>> So I'd like to step up as new maintainer.
> >>>>
> >>>> Signed-off-by: Helge Deller <deller@....de>
> >>>>
> >>>> diff --git a/MAINTAINERS b/MAINTAINERS
> >>>> index 5d0cd537803a..ce47dbc467cc 100644
> >>>> --- a/MAINTAINERS
> >>>> +++ b/MAINTAINERS
> >>>> @@ -7583,11 +7583,12 @@ W:      http://floatingpoint.sourceforge.net/emulator/index.html
> >>>>  F:     arch/x86/math-emu/
> >>>>
> >>>>  FRAMEBUFFER LAYER
> >>>> -L:     dri-devel@...ts.freedesktop.org
> >>>> +M:     Helge Deller <deller@....de>
> >>>>  L:     linux-fbdev@...r.kernel.org
> >>>> -S:     Orphan
> >>>
> >>> Maybe don't rush maintainer changes in over the w/e without even bothering
> >>> to get any input from the people who've been maintaining it before.
> >>>
> >>> Because the status isn't entirely correct, fbdev core code and fbcon and
> >>> all that has been maintained, but in bugfixes only mode. And there's very
> >>> solid&important reasons to keep merging these patches through a drm tree,
> >>> because that's where all the driver development happens, and hence also
> >>> all the testing (e.g. the drm test suite has some fbdev tests - the only
> >>> automated ones that exist to my knowledge - and we run them in CI). So
> >>> moving that into an obscure new tree which isn't even in linux-next yet is
> >>> no good at all.
> >>>
> >>> Now fbdev driver bugfixes is indeed practically orphaned and I very much
> >>> welcome anyone stepping up for that, but the simplest approach there would
> >>> be to just get drm-misc commit rights and push the oddball bugfix in there
> >>> directly. But also if you want to do your own pull requests to Linus for
> >>> that I don't care and there's really no interference I think, so
> >>> whatever floats.
> >>>
> >>> But any code that is relevant for drm drivers really needs to go in through
> >>> drm trees, nothing else makes much sense.
> >>>
> >>> I guess you're first action as newly minted fbdev maintainer is going to be to
> >>> clean up the confusion you just created.
> >>
> >> Most of my machines depend on a working fbdev layer since drm isn't (and probably
> >> -due to technical requirements of DRM- won't be) available for those.
> >> So, since the fbdev drivers were marked orphaned, I decided to step up as maintainer.
> >>
> >> I see your point that at least the fbdev core code and fbcon are shared between DRM and fbdev.
> >> For me it's really not important to drive any patches through a seperate tree, so
> >> I'd be happy to join the drm-misc tree if you feel it's necessary. (By the way,
> >> adding my tree to for-next was on my todo list...)
> >>
> >> What's important for me though is, to keep fbdev actively maintained, which means:
> >> a) to get fixes which were posted to fbdev mailing list applied if they are useful & correct,
> >
> > Yeah it'd be great if we have that, for a while Bart took care of
> > these, but had to step down again. drm-misc is maintained with the dim
> > scrip suite, which comes with docs and bash completion and everything.
> > Good starting pointer is here:
> >
> > https://drm.pages.freedesktop.org/maintainer-tools/getting-started.html
> >
> > Process for getting commit rights is documented here:
> >
> > https://drm.pages.freedesktop.org/maintainer-tools/commit-access.html#drm-misc
> >
> > But there's a pile more. I think once we've set that up and got it
> > going we can look at the bigger items. Some of them are fairly
> > low-hanging fruit, but the past 5+ years absolutely no one bothered to
> > step up and sort them out. Other problem areas in fbdev are extremely
> > hard to fix properly, without only doing minimal security-fixes only
> > support, so fair warning there. I think a good starting point would be
> > to read the patches and discussions for some of the things you've
> > reverted in your tree.
> >
> > Anyway I hope this gets you started, and hopefully after a minor
> > detour: Welcome to dri-devel, we're happy to take any help we can get,
> > there's lots to do!
> >
>
> Hello Daniel,
>
> you somehow missed to answer my main topics below...:

Well others replied on some specifics already, but for your reverts
really read the commit message first. fbcon is full or broken locking
and crashes that syzbot hits, so if you want to resurrect that code,
those bugs need to be fixed first. Or at least some way to make sure
that only people who don't care about serious issues in their kernel
can use the code. We haven't done much maintainering, but we've tried
to at least somewhat stay on top of the oopses and issues syzbot
discovers (not even all of them unfortunately).

Wrt useable console: shadow buffer + memcpy tends to be most
performant, actually useful 2d acceleration is really hard. See the
blog post Thomas linked. If you go with that, drm has you fully
covered.

None of the things you bring up are anything new really, and have been
discussed at length over the past 5-10 years here on dri-devel. That's
why I suggested that a good start is to focus on the simple fixes
first, and meanwhile ramp up on the complexity you're volunteering
for. There's some really tricky things going on here.
-Daniel

> >
> >> b) to include new drivers (for old hardware) if they arrive (probably happens rarely but there can be).
> >>    I know of at least one driver which won't be able to support DRM....
> >>    Of course, if the hardware is capable to support DRM, it should be written for DRM and not applied for fbdev.
> >> c) reintroduce the state where fbcon is fast on fbdev. This is important for non-DRM machines,
> >>    either when run on native hardware or in an emulator.
> >> d) not break DRM development
> >>
> >> Especially regarding c) I complained in [1] and got no feedback. I really would like to
> >> understand where the actual problems were and what's necessary to fix them.
> >>
> >> Helge
> >>
> >> [1] https://lore.kernel.org/r/feea8303-2b83-fc36-972c-4fc8ad723bde@gmx.de
> >
> >
> >
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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