[PATCH xorgproto 1/2] randr: Add Leases. [v4]

[Adam Jackson]

On Mon, 2018-02-05 at 12:39 -0800, Keith Packard wrote:

>  randrproto.pc.in                    |  2 +-

Please be sure to bump the pc version in meson.build too. (If there's a
more convenient way to only bump things once, great, let's do that
instead.)

> +7.6. Extension Requests added in version 1.6 of the extension.
> +
> +┌───
> +    RRCreateLease
> +	window : WINDOW
> +	lid: LEASE
> +	crtcs: LISTofCRTC
> +	outputs: LISTofOUTPUT
> +     ▶
> +	nfd: CARD8
> +	lease: FD
> +└───
> +	Errors: IdChoice, Window, Access, Value, CRTC, Output
> +
> +	Creates a new Lease called 'lid' for the specified crtcs and
> +	outputs from the screen defined by 'window'. Returns a KMS/DRM
> +	file descriptor which can control the leased objects directly
> +	through the kernel. While leased, all resources will appear to
> +	be 'useless' to clients other than the leasing client as
> +	follows:
> +
> +	• Crtcs are reported as having no 'possible-outputs' and all
> +	  other values reported as if the crtc were disabled.
> +
> +	• Outputs are reported as having no crtcs they can be
> +	  connected to, no clones they can share a crtc with, will
> +	  report a connection status of Disconnected, and will show
> +	  the current crtc as if it were disabled.
> +
> +	The lease remains in effect until the file descriptor is
> +	closed, even if the client holding the lease disconnects from
> +	the X server.
> +
> +	Returns an Access error if any of the named resources are
> +	already leased to another client.

This should throw something if it's not possible to pass fds to the
client (presumably because it's non-local). BadAccess or BadMatch seem
like good ideas.

Also I'm a little nervous about just returning a file descriptor
without any way to describe what kind of operations you can do with it;
if we ever develop an output setup API we hate less than KMS we'll have
painted ourselves into a corner. Should this fd come with an atom
naming an ioctl protocol? Should we apply that atom to the crtc[s] as
well so the client can know the protocol in advance?

- ajax