man/io_uring_register.2: improve IORING_REGISTER_BUFFERS2 description

The section on IORING_REGISTER_BUFFERS_UPDATE mentions sparse entries, so described how they can be registered. Also improved formatting. Signed-off-by: Wojciech Łukowicz <[email protected]>
wlukowicz · Dec 1, 2024 · 416d96c · 416d96c
1 parent dbe9fbf
commit 416d96c
Showing 1 changed file with 23 additions and 8 deletions.
diff --git a/man/io_uring_register.2 b/man/io_uring_register.2
@@ -113,27 +113,25 @@ but aims to have a more extensible ABI.
 
 .I arg
 points to a
-.IR struct io_uring_rsrc_register ,
+.I struct
+.IR io_uring_rsrc_register ,
 and
 .I nr_args
 should be set to the number of bytes in the structure.
 
-.PP
-.in +8n
+.IP
+.in +4n
 .EX
 struct io_uring_rsrc_register {
     __u32 nr;
-    __u32 resv;
+    __u32 flags;
     __u64 resv2;
     __aligned_u64 data;
     __aligned_u64 tags;
 };
-
 .EE
 .in
-.PP
-
-.in +8n
+.IP
 
 The
 .I data
@@ -154,6 +152,23 @@ posted with
 .I user_data
 set to the specified tag and all other fields zeroed.
 
+The
+.I flags
+field supports the following flags:
+
+.IP
+.in +4n
+.B IORING_RSRC_REGISTER_SPARSE
+If set, io_uring will register
+.I nr
+empty buffers, which need to be updated before use. When this flag is set,
+.I data
+and
+.I tags
+must be NULL. Available since 5.19.
+.in
+.IP
+
 Note that resource updates, e.g.
 .BR IORING_REGISTER_BUFFERS_UPDATE ,
 don't necessarily deallocate resources by the time it returns, but they might