man/io_uring_setup.2: document missing IORING_FEAT_* feature flags
@@ -113,13 +113,20 @@ is a submission queue ring setup using the
described below.
.TP
.BR
-To successfully use this feature, the application must register a set of files
-to be used for IO through
+Before version 5.10 of the Linux kernel, to successfully use this feature, the
+application must register a set of files to be used for IO through
.BR io_uring_register (2)
using the
.B IORING_REGISTER_FILES
opcode. Failure to do so will result in submitted IO being errored with
.B EBADF.
+The presence of this feature can be detected by the
+.B IORING_FEAT_SQPOLL_NONFIXED
+feature flag.
+In version 5.10 and later, it is no longer necessary to register files to use
+this feature. 5.10 also allows using this as non-root, if the user has the
+.B CAP_SYS_NICE
+capability.
.TP
.B IORING_SETUP_SQ_AFF
If this flag is specified, then the poll thread will be bound to the
@@ -234,6 +241,28 @@ io_uring_register(2)
with
.B IORING_REGISTER_PERSONALITY
and specify the personality to use in the sqe.
+.TP
+.B IORING_FEAT_FAST_POLL
+If this flag is set, then io_uring supports using an internal poll mechanism
+to drive data/space readiness. This means that requests that cannot read or
+write data to a file no longer need to be punted to an async thread for
+handling, instead they will being operation when the file is ready. This is
+similar to doing poll + read/write in userspace, but eliminates the need to do
+so. If this flag is set, requests waiting on space/data consume a lot less
+resources doing so as they are not blocking a thread.
+.TP
+.B IORING_FEAT_POLL_32BITS
+If this flag is set, the
+.B IORING_OP_POLL_ADD
+command accepts the full 32-bit range of epoll based flags. Most notably
+.B EPOLLEXCLUSIVE
+which allows exclusive (waking single waiters) behavior.
+.TP
+.B IORING_FEAT_SQPOLL_NONFIXED
+If this flag is set, the
+.B IORING_SETUP_SQPOLL
+feature no longer requires the use of fixed files. Any normal file descriptor
+can be used for IO commands without needing registration.
.PP
The rest of the fields in the
