[Mesa-dev] [PATCH 5/7] vulkan: add VK_EXT_display_control [v5]

Keith Packard keithp at keithp.com
Wed Jun 20 22:49:56 UTC 2018

Jason Ekstrand <jason at jlekstrand.net> writes:

> That seems good to me.  Unless, of course, DPMS is something we expect to
> change over time somehow.  Then again, we don't handle that at all right
> now so meh.  Let's go with what you wrote above for now.

It's not even the dpms value, it's the dpms property itself, which
DRM never changes.

> They shouldn't be and that's why I'm a fan of making them asserts which get
> compiled out instead of actual checks.  Also, I find this pseudo reference
> counting to be somewhat confusing and adding asserts informs the reader of
> the assumptions made.

Ok, I've added this.

> What test suite?  Honestly, I know of no code anywhere that actually uses
> this API for anything other than VR headsets.
> I guess it's kind-of a question of how much effort we want to put into
> this.  One option would be to add VK_KHR_display support to vkcube and make
> it automatically show up on all your displays using hotplug events.
> If we're going to not care, returning VK_ERROR_FEATURE_NOT_PRESENT is
> probably the best thing to do since at least the app has feedback.

Not caring seems best to me -- the Vulkan display API isn't capable of
supporting a "real" window system; for that, you'd really want to use
DRM directly and create some way to share that with Vulkan like the
extension I wrote to pass the DRM master FD into the driver at init time.

> Awesome.  I think we're really close on this one.

I'll send out the current series and you can see if you like it.

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