[Intel-xe] [PATCH] fixup! drm/xe/uapi: support pat_index selection with vm_bind

[Matthew Auld]

Add a note in the docs for NULL bindings and corresponding pat_index:

https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26430

Testcase: igt at xe_pat@pat-index-all
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
Cc: José Roberto de Souza <jose.souza at intel.com>
---
 include/uapi/drm/xe_drm.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
index 58e655981992..1a844fa7af8a 100644
--- a/include/uapi/drm/xe_drm.h
+++ b/include/uapi/drm/xe_drm.h
@@ -673,6 +673,12 @@ struct drm_xe_vm_bind_op {
 	 *
 	 * Note: For userptr and externally imported dma-buf the kernel expects
 	 * either 1WAY or 2WAY for the @pat_index.
+	 *
+	 * For DRM_XE_VM_BIND_FLAG_NULL bindings there are no KMD restrictions
+	 * on the @pat_index. For such mappings there is no actual memory being
+	 * mapped (the address in the PTE is invalid), so the various PAT memory
+	 * attributes likely do not apply.  Simply leaving as zero is one
+	 * option (still a valid pat_index).
 	 */
 	__u16 pat_index;
 
-- 
2.43.0