diff --git a/libusb.odin b/libusb.odin
index cae68b6..af336eb 100644
--- a/libusb.odin
+++ b/libusb.odin
@@ -2,6 +2,7 @@ package libusb
 
 import "core:c"
 import "core:fmt"
+import "core:sys/posix"
 
 //TODO: Probably want to switch this to being statically linked
 foreign import lib "system:usb-1.0"
@@ -804,8 +805,7 @@ Transfer_Status :: enum c.int {
 	OVERFLOW,
 }
 
-// This is not compatible with the C enum and is meant to always be used with [Transfer_Set].
-Transfer_Flags :: enum u8 {
+Transfer_Flag_Bits :: enum u8 {
 	/** Report short frames as errors */
 	SHORT_NOT_OK,
 	/** Automatically free() transfer buffer during libusb_free_transfer().
@@ -845,7 +845,7 @@ Transfer_Flags :: enum u8 {
 	ADD_ZERO_PACKET,
 }
 
-Transfer_Set :: bit_set[Transfer_Flags;u8]
+Transfer_Flag :: bit_set[Transfer_Flag_Bits;u8]
 
 /** \ingroup libusb_asyncio
  * Isochronous packet descriptor. */
@@ -870,7 +870,7 @@ Transfer :: struct {
 	/** Handle of the device that this transfer will be submitted to */
 	dev_handle:      ^Device_Handle,
 	/** A bitwise OR combination of \ref libusb_transfer_flags. */
-	flags:           Transfer_Set,
+	flags:           Transfer_Flag,
 	/** Address of the endpoint where this transfer will be sent. */
 	endpoint:        c.char,
 	/** Type of the transfer from \ref libusb_transfer_type */
@@ -1076,7 +1076,7 @@ HOTPLUG_NO_FLAGS :: 0
  * Wildcard matching for hotplug events */
 HOTPLUG_MATCH_ANY :: -1
 
-Hotplug_Callback_Fn :: #type proc "c" (
+Hotplug_Callback :: #type proc "c" (
 	ctx: Context,
 	device: ^Device,
 	event: Hotplug_Event,
@@ -1084,6 +1084,51 @@ Hotplug_Callback_Fn :: #type proc "c" (
 ) -> c.int
 Callback_Handle :: distinct c.int
 
+Transfer_Type :: enum c.int {
+	CONTROL     = 0,
+	ISOCHRONOUS = 1,
+	BULK        = 2,
+	INTERRUPT   = 3,
+	STREAM      = 4,
+}
+
+/** \ingroup libusb_asyncio
+ * Transfer status codes */
+Transfer_Status :: enum c.int {
+	/** Transfer completed without error. Note that this does not indicate
+	 * that the entire amount of requested data was transferred. */
+	COMPLETED,
+	/** Transfer failed */
+	ERROR,
+	/** Transfer timed out */
+	TIMED_OUT,
+	/** Transfer was cancelled */
+	CANCELLED,
+	/** For bulk/interrupt endpoints: halt condition detected (endpoint
+	 * stalled). For control endpoints: control request not supported. */
+	STALL,
+	/** Device was disconnected */
+	NO_DEVICE,
+	/** Device sent more data than requested */
+	OVERFLOW,
+	/* NB! Remember to update libusb_error_name()
+	   when adding new status codes here. */
+}
+
+Poll_Fd :: struct {
+	/** Numeric file descriptor */
+	fd:     posix.FD,
+	/** Event flags to poll for from <poll.h>. POLLIN indicates that you
+	 * should monitor this file descriptor for becoming ready to read from,
+	 * and POLLOUT indicates that you should monitor this file descriptor for
+	 * nonblocking write readiness. */
+	events: posix.Poll_Event,
+}
+
+Poll_FD_Added_CB :: #type proc "c" (fd: posix.FD, events: posix.Poll_Event, user_date: rawptr)
+
+Poll_FD_Removed_CB :: #type proc "c" (fd: posix.FD, user_data: rawptr)
+
 @(default_calling_convention = "c", link_prefix = "libusb_")
 foreign lib {
 	//----- Library initialization/deinitialization ----------------------------------
@@ -1158,7 +1203,36 @@ foreign lib {
 	hotplug_deregister_callback :: proc(ctx: Context, hotplug_callback_handle: Callback_Handle) ---
 	hotplug_get_user_data :: proc(ctx: Context, hotplug_callback_handle: Callback_Handle) -> rawptr ---
 
-	//TODO: Asynchronous device I/O
+	//----- Asynchronous device I/O ----------------------------------
+	alloc_streams :: proc(dev_handle: Device_Handle, num_streams: u32, endpoints: [^]u8, num_endpoints: c.int) -> c.int ---
+	free_streams :: proc(dev_handle: Device_Handle, endpoints: [^]u8, num_endpoints: c.int) -> Error ---
+	dev_mem_alloc :: proc(dev_handle: Device_Handle, length: c.size_t) -> [^]u8 ---
+	dev_mem_free :: proc(dev_handle: Device_Handle, buffer: [^]u8, length: c.size_t) -> Error ---
+	alloc_transfer :: proc(iso_packets: c.int = 0) -> ^Transfer ---
+	free_transfer :: proc(transfer: ^Transfer) ---
+	submit_transfer :: proc(transfer: ^Transfer) -> Error ---
+	cancel_transfer :: proc(transfer: ^Transfer) -> Error ---
+	transfer_set_stream_id :: proc(transfer: ^Transfer, stream_id: u32) ---
+	transfer_get_stream_id :: proc(transfer: ^Transfer) -> u32 ---
+
+	//----- Polling and timing ----------------------------------
+	try_lock_events :: proc(ctx: Context) -> c.int ---
+	lock_events :: proc(ctx: Context) ---
+	unlock_events :: proc(ctx: Context) ---
+	event_handling_ok :: proc(ctx: Context) -> c.int ---
+	event_handler_active :: proc(ctx: Context) -> c.int ---
+	interrupt_event_handler :: proc(ctx: Context) ---
+	lock_event_waiters :: proc(ctx: Context) ---
+	unlock_event_waiters :: proc(ctx: Context) ---
+	wait_for_event :: proc(ctx: Context, tv: ^posix.timeval) -> c.int ---
+	handle_events_timeout_completed :: proc(ctx: Context, tv: ^posix.timeval, completed: ^c.int) -> Error ---
+	handle_events_completed :: proc(ctx: Context, completed: ^c.int) -> Error ---
+	handle_events_locked :: proc(ctx: Context, tv: ^posix.timeval) -> Error ---
+	pollfds_handle_timeouts :: proc(ctx: Context) -> c.int ---
+	get_next_timeout :: proc(ctx: Context, tv: ^posix.timeval) ---
+	set_poll_fd_notifiers :: proc(ctx: Context, added_cb: Poll_FD_Added_CB, removed_cb: Poll_FD_Removed_CB, user_data: rawptr) ---
+	get_pollfds :: proc(ctx: Context) -> ^[^]Poll_Fd ---
+	free_fds :: proc(pollfds: ^[^]Poll_Fd) ---
 
 	//----- Synchronous device I/O ----------------------------------
 	control_transfer :: proc(dev_handle: ^Device_Handle, bmRequestType: u8, bRequest: u8, wValue: u16, wIndex: u16, data: [^]u8, wLength: u16, timeout: c.uint) -> Error ---