HWC2: Clarify null client target handle

Documentation-only change that clarifies that in the case where the
client isn't compositing any of the layers, the buffer handle
provided to setClientTarget may be null, and that this should not be
treated as an error by the device.

Bug: 28569722
Change-Id: Ia5825eb0a80c7f838894642654db7d7be14a3b6b

diff --git a/include/hardware/hwcomposer2.h b/include/hardware/hwcomposer2.h
index 095557a..f42456b 100644 (file)
--- a/include/hardware/hwcomposer2.h
+++ b/include/hardware/hwcomposer2.h
@@ -1384,6 +1384,10 @@ typedef int32_t /*hwc2_error_t*/ (*HWC2_PFN_SET_ACTIVE_CONFIG)(
  * prior to the call to presentDisplay, and layers not marked as
  * HWC2_COMPOSITION_CLIENT should be composited with this buffer by the device.
  *
+ * The buffer handle provided may be null if no layers are being composited by
+ * the client. This must not result in an error (unless an invalid display
+ * handle is also provided).
+ *
  * Also provides a file descriptor referring to an acquire sync fence object,
  * which will be signaled when it is safe to read from the client target buffer.
  * If it is already safe to read from this buffer, -1 may be passed instead.