From df9a4e7bf4fc264c4992acc96e8ac737768c291b Mon Sep 17 00:00:00 2001
From: Drew DeVault <sir@cmpwn.com>
Date: Tue, 18 May 2021 17:42:22 -0400
Subject: [PATCH] linux::io_uring: add polling SQEs

Signed-off-by: Drew DeVault <sir@cmpwn.com>

---
 io_uring/sqe.ha | 30 ++++++++++++++++++++++++++++++

diff --git a/io_uring/sqe.ha b/io_uring/sqe.ha
index 14492cd066fc6c06d092c45116a7ca174577a711..b6c2070b85a39b43bc2183db9cbace0728aa2ad3 100644
--- a/io_uring/sqe.ha
+++ b/io_uring/sqe.ha
@@ -1,3 +1,4 @@
+use endian;
 use rt;
 use types;
 
@@ -23,6 +24,13 @@ 	sqe.fd = fd;
 	sqe.addr = addr;
 	sqe.length = length;
 	sqe.off = offs;
+};
+
+// Sets the user data field of an [[sqe]]. This is copied to the [[cqe]] and can
+// be used to correlate a completion event with the original SQE.
+export fn setuser(sqe: *sqe, user_data: *void) void = {
+	static assert(size(uintptr) <= size(u64));
+	sqe.user_data = user_data: uintptr: u64;
 };
 
 // Prepares a no-op "operation" for an [[sqe]].
@@ -123,3 +131,25 @@ ) void = {
 	preprw(sqe, op::FSYNC, fd, null, 0, 0, flags...);
 	sqe.fsync_flags = fsync_flags;
 };
+
+// Adds a request to poll a file descriptor for the given set of poll events.
+// This will only happen once, the poll request must be submitted with a new SQE
+// to re-poll the file descriptor later. The caller must call [[setuser]] to
+// provide a user data field in order to use [[poll_remove]] to remove this poll
+// request later.
+export fn poll_add(
+	sqe: *sqe,
+	fd: int,
+	poll_mask: uint,
+	flags: sqe_flags...
+) void = {
+	preprw(sqe, op::POLL_ADD, fd, null, 0, 0, flags...);
+	assert(endian::host == &endian::little); // TODO?
+	sqe.poll32_events = poll_mask: u32;
+};
+
+// Removes an existing poll request by matching the SQE's user_data field.
+export fn poll_remove(sqe: *sqe, user_data: *void, flags: sqe_flags...) void = {
+	preprw(sqe, op::POLL_REMOVE, -1, null, 0, 0, flags...);
+	setuser(sqe, user_data);
+};

-- 
2.48.1