[PATCH] Clarify the cases where BLKIF_RSP_EOPNOTSUPP can be returned.

[Mark Syms <mark.syms@cloud.com>]

Previously this said it would only happen on barrier writes. Except
the documentation blocks for
 * feature-flush-cache
 * feature-discard

Also say that they can return this error.

Signed-off-by: Mark Syms <mark.syms@cloud.com>
---
 xen/include/public/io/blkif.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
index 8407453324..5e617b0c67 100644
--- a/xen/include/public/io/blkif.h
+++ b/xen/include/public/io/blkif.h
@@ -710,7 +710,7 @@ typedef struct blkif_response blkif_response_t;
 /*
  * STATUS RETURN CODES.
  */
- /* Operation not supported (only happens on barrier writes). */
+ /* Operation not supported, see feature-barrier, feature-flush-cache, feature-discard. */
 #define BLKIF_RSP_EOPNOTSUPP  -2
  /* Operation failed for some unspecified reason (-EIO). */
 #define BLKIF_RSP_ERROR       -1
-- 
2.50.1