[PATCH 1/2] drm/core: Preserve the framebuffer after removing it.

[David Herrmann]

Hi

On Wed, Sep 9, 2015 at 5:02 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Wed, Sep 09, 2015 at 04:40:56PM +0200, Maarten Lankhorst wrote:
>> Previously RMFB and fd close chose to disable any plane that had
>> an active framebuffer from this file. If it was a primary plane the
>> crtc was disabled. However the fbdev code or any system compositor
>> should restore the planes anyway so there's no need to do it twice.
>>
>> The old fb_id is zero'd, so there's no danger of being able to
>> restore the fb from fb_id.
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>
> I think the current behaviour was just a side-effect of the original
> implementation and not too intentional - with no refcounting for fbs they
> _had_ to be synchronously reaped. And when I've done the conversion to
> refcounting I kept this to avoid gettting tangled up in an ABI-change
> mess.
>
> But I don't the current behaviour makes much sense and worth an attemp to
> rectify it. And as long as we still clear the fb ids there's no real
> information leak either.
>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> But I do want other people's opinion before I pull this in.

We _REALLY_ want this! It makes a lot of our life much easier when
trying to get rid of flicker during boot-up. It currently sucks that
neither the boot-loader screen, nor the boot-splash screen, nor the
login-manager screen can be left around after they quit and handover
to the next stage. We have to stay around for hand-over, which is
nasty and requires a back-channel which is otherwise not needed at
all.

Reviewed-by: David Herrmann <dh.herrmann at gmail.com>

Thanks
David