On 11/04/2011 04:34 PM, Daniel Vetter wrote:
On Fri, Nov 04, 2011 at 12:59:59PM +0100, Thomas Hellstrom wrote:
Hi.
I have a question about the semantics of the DRM_IOCTL_MODE_CURSOR iotcl:
Some hardware (vmware's virtual in particular) may not be able to
pick up the changes from a bo directly, since the cursor data is
sent though the command stream. Hence we need a notification when
the cursor image has changed.
Could we *require* that a cursor image change needs to be followed
by an ioctl call with the flag
DRM_MODE_CURSOR_BO?
On i915 we need the cursor in physical memory for some (old) platforms,
which is seperate storage from the bo backing storage. So we have the same
problem. We've solved it by intercepting pwrite ioctl calls and demanding
that userspace only uses these for cursor updates. Is there a special
reason you can't use such a driver-specific trick?
-Daniel
We have something similar in use today: We snoop DMAs to hardware
cursor surfaces, but this gets a bit nasty when apps start to do
hardware render to cursor surfaces, and
we simply ignore that today.
Furthermore, maps rather than pwrites are the common usage-pattern for
buffer-backed cursors on vmwgfx, and while it's possible to dirty those
buffers based on page-faults, like we do with fb surfaces, we'd rather
avoid having to implement and maintain that.
I'm not sure whether / how you handle the case of hardware render to
cursor surfaces on i915, but it seems to me like if a lot of drivers
need to implement driver specific "tricks" to meet the semantics of a
generic interface, we should perhaps consider specifying those semantics
in a way that helps avoid driver-specific workarounds?
/Thomas
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/dri-devel
