Re: [PATCH v2 12/12] JUST FOR TEST: Add one-shot trigger to update display

From: Mark Zhang <markz-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
To: Daniel Vetter <daniel-/w4YWyX8dFk@public.gmane.org>
Cc: thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org
Subject: Re: [PATCH v2 12/12] JUST FOR TEST: Add one-shot trigger to update display
Date: Fri, 3 Jul 2015 15:57:55 +0800	[thread overview]
Message-ID: <55964083.60001@nvidia.com> (raw)
In-Reply-To: <20150701145535.GW23343-dv86pmgwkMBes7Z6vYuT8azUEOm+Xw19@public.gmane.org>

On 07/01/2015 10:55 PM, Daniel Vetter wrote:
> On Wed, Jul 01, 2015 at 08:43:01PM +0800, Mark Zhang wrote:
>> On 07/01/2015 06:34 PM, Daniel Vetter wrote:
[...]
>>>
>>
>> Alright, this makes sense. I have no idea about qxl, what I have now is
>> an ubuntu running on Tegra114. So I'm wondering what I suppose to do is
>> installing qemu on the ubuntu?
> 
> My suggestion is just to take the qxl code, move it to the fbdev emulation
> helper, make it generic and use it. If you want you can do a
> compile-tested patch on top to switch qxl over to the newly added helpers.
> No need to install/run qxl itself. Just that qxl seems to have the most
> complete solution for what you need.

OK, thanks Daniel. I'm not quite familiar with the userspace, but I
think this is the summary:

- For legacy FB support, we can use the "->dirty" fops, port the qxl
codes to drm_fb_helper.c, just as you described.
- For atomic page flip, the one-shot can be triggered when flipping the
window/plane.
- How about the front buffer rendering/drawing? I mean, if a drm
userspace app requests a dumb buffer then draws on it, how can we
trigger the one-shot to update the display? Do we need to add an
additional IOCTL to do that?

Mark
> -Daniel
> 