[Intel-gfx] [PATCH 3/4] drm: Only lastclose on unload for legacy drivers

[Alex Deucher]

On Thu, Aug 3, 2017 at 9:54 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> On Thu, Aug 3, 2017 at 1:17 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>> On Wed, Aug 2, 2017 at 10:50 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
>>> On Wed, Aug 2, 2017 at 7:56 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>>>> The only thing modern drivers are supposed to do in lastclose is
>>>> restore the fb emulation state. Which is entirely optional, and
>>>> there's really no reason to do that. So restrict it to legacy drivers
>>>> (where the driver cleanup essentially happens in lastclose).
>>>
>>> vga_switcheroo_process_delayed_switch() gets called in lastclose.
>>> Won't that need to get moved elsewhere for this to work?
>>
>> Hm right, I forgot the lazy way to do runtime pm by keeping the device
>> alive as long as anyone has an open fd for it ... This shouldn't be a
>> problem, since you need to unregister from vgaswitcheroo anyway on
>> unload. Maybe that blows up, I'll check the code and augment the patch
>> as needed.
>
> So I think there's 3 cases:
> - Trying to unload the module. You can't do that while anyone has the
> fd still open, so lastclose is guaranteeed to run.
> - Forcefully unbinding the driver through sysfs. Not any better, since
> the can_switch stuff checks for the open count, and so will delay the
> delayed switch no matter what.
> - Actual hotremoval: a) not implemented since none of the drivers
> taking part in vgaswitcheroo correctly unplug the drm device and b)
> you can't hotremove a chip from a laptop.
>
> So I think I'm not breaking this anymore than it probably already is :-)

Thanks.  This series is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

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