drm/i915: Return a mask of the active rings in the high word of busy_ioctl

The intention is to help select which engine to use for copies with
interoperating clients - such as a GL client making a request to the X
server to perform a SwapBuffers, which may require copying from the
active GL back buffer to the X front buffer.

We choose to report a mask of the active rings to future proof the
interface against any changes which may allow for the object to reside
upon multiple rings.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: bikeshed away the write ring mask and add the explanation
Chris sent in a follow-up mail why we decided to use masks.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 5c4657a54f97..4be096068b35 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3400,6 +3400,10 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
         ret = i915_gem_object_flush_active(obj);
 
         args->busy = obj->active;
+        if (obj->ring) {
+                BUILD_BUG_ON(I915_NUM_RINGS > 16);
+                args->busy |= intel_ring_flag(obj->ring) << 16;
+        }
 
         drm_gem_object_unreference(&obj->base);
 unlock: