Message-ID: <CAKMK7uHvvqwrLWpbfz4saPNTRB4q1hOv671bxkG9RzUHso9fyA@mail.gmail.com>
Date:   Wed, 20 Dec 2017 16:22:25 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Max Staudt <mstaudt@...e.de>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        michal@...kovi.net, sndirsch@...e.com,
        Oliver Neukum <oneukum@...e.com>,
        Takashi Iwai <tiwai@...e.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bero Rosenkränzer 
        <bernhard.rosenkranzer@...aro.org>, philm@...jaro.org
Subject: Re: [RFC PATCH v2 00/13] Kernel based bootsplash

On Wed, Dec 20, 2017 at 4:19 PM, Daniel Vetter <daniel@...ll.ch> wrote:
> On Wed, Dec 20, 2017 at 4:11 PM, Daniel Vetter <daniel@...ll.ch> wrote:
>> On Wed, Dec 20, 2017 at 3:55 PM, Max Staudt <mstaudt@...e.de> wrote:
>>> On 12/20/2017 11:14 AM, Daniel Vetter wrote:
>>>> btw since I'm probably sounding a bit too grumpy here: I'd very much
>>>> support this. I think bootsplash in kernel has a bunch of uses, and it
>>>> shouldn't be hard to get non-suse people to cheer for it (makes merging
>>>> easier if it's not just a one-off hack).
>>>
>>> Thank you!
>>>
>>> As it seems, other people and distros are already interested - for example Manjaro.
>>>
>>> It's also a chance to (maybe in the near future) integrate with a splash painted by EFI and/or GRUB, before userspace has even started.
>>
>> Maybe I've sounded too optimistic now.
>>
>> So fundamentally I don't think an in-kernel bootsplash is a bad idea.
>> But most likely you want this on a highly embedded system, which
>> probably is compiled for your exact hw, with pretty much everything
>> built in. Also, no fbcon, maybe even no vt subsystem at all.
>> Definitely not your general purpose distro.
>>
>> Your proposal to work on top of fbcon doesn't fix that niche.
>>
>> Now for your problem, which seems to be to have a working bootsplash
>> for a general purpose distro, specifically for the bug where plymouth
>> prevents the real drm driver from loading: Adding an in-kernel
>> bootsplash doesn't make any sense, at least not to me. Instead I think
>> the right action is to fix the problem, both in the kernel and in
>> userspace.
>>
>> All the problems below have fairly simple solutions, but there's imo
>> no point in talking technical solutions for specific problems when
>> we're trying to fix the wrong problem.
>
> Aside: The problem you think you need the vt/console subsystem for is
> simple to fix with plain kms: kms works without fbdev, fbcon and the
> entire vt subsystem. Dislay ownership is controlled through the drm
> master concept. That's the exact same trick that we're using already
> to figure out whether fbdev (not just fbcon) is allowed to touch the
> display hw.
>
> So yeah, there's a solution, and a modern system definitely would not
> want to get encumbered with the entire vt subsystem to be able to use
> a bootsplash. David Herrman had the entire pile prototyped btw,
> including userspace console on top of drm, emergency log on top of
> drm, and replacement for simpledrm. Adding an in-kernel boot splash
> would be fairly simple for this setup. It's just that no one else
> cared enough to get it merged.

*replacement for efifb/vesafb in the form of simpledrm. The
in-userspace fbcon is called kmscon, so also exists already. The
emergency boot splash thing was called drmlog iirc.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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