linux-kernel - Re: [PATCH v4 3/7] drm/fb-helper: Add fb_deferred

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Message-ID: <CAKMK7uGHcfcJv0gU3Tn2x3BxhozxKUuHrX6j0AODwo2+A0hJ+A@mail.gmail.com>
Date:	Fri, 29 Apr 2016 17:38:08 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Noralf Trønnes <noralf@...nnes.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Herrmann <dh.herrmann@...il.com>
Subject: Re: [PATCH v4 3/7] drm/fb-helper: Add fb_deferred_io support

Adding David, forgot that before hitting send.
-Daniel

On Fri, Apr 29, 2016 at 5:36 PM, Daniel Vetter <daniel@...ll.ch> wrote:
> On Fri, Apr 29, 2016 at 06:00:18PM +0300, Tomi Valkeinen wrote:
>>
>> On 29/04/16 17:55, Daniel Vetter wrote:
>>
>> >> Who's calling {write,fillrect,copyarea,imageblit} in an atomic context?
>> >> That sounds like a very bad idea to me...
>> >>
>> >> If this is only for accumulating changes, I think it may be better to
>> >> leave that to the driver as it may have better idea of how to accumulate.
>> >>
>> >> But, of course, this is a helper, so if all the drivers use this kind of
>> >> accumulation, it makes sense =).
>> >
>> > Apparently panic context and cursor timer and stuff like that. I think
>> > this started with udl, and just to make sure (it's fbdev after all, no one
>> > wants to read the code itself) we've put those checks onto all entry
>> > points that draw stuff. It could be overkill, but this is what udl/qxl
>> > already do, so better to keep imo for now.
>> >
>> > I guess if it's really not needed we could later on change that, but not
>> > sure that's worth the effort. And we can't get rid of it entirely.
>>
>> Yep... Sounds fine to me.
>>
>> Someone should implement (minimal) fbdev userspace API support to DRM
>> without using the current fbdev, and implement fbcon on top of that. I
>> don't like how DRM and fbdev gets mixed...
>>
>> I offer a beer to anyone who does that =).
>
> The big plan that has been floated years back already (before David
> Herrmann disappeared into the rh systemd gang) was to have a pure
> userspace kmscon for console (including vt-switching in userspace like X
> does), plus a super-minimal panic console on top of kms in the kernel.
> That looked like a really solid design, unfornutately it didn't go
> anywhere. But basic patches are still around, and it really just boils
> down to that some distro would need to integrate kmscon properly, and
> polish of the kernel side too for integration.
> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch