MEDIUM: fd: simplify the fd_*_{recv,send} functions using BTS/BTR
Now that we don't have to update FD_EV_POLLED_* at the same time as
FD_EV_ACTIVE_*, we don't need to use a CAS anymore, a bit-test-and-set
operation is enough. Doing so reduces the code size by a bit more than
1 kB. One function was special, fd_done_recv(), whose comments and doc
were inaccurate for the part related to the lack of polling.
diff --git a/include/types/fd.h b/include/types/fd.h
index 6794d74..28f0c52 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -52,7 +52,10 @@
#define FD_EV_READY 2U
/* bits positions for a few flags */
+#define FD_EV_ACTIVE_R_BIT 0
#define FD_EV_READY_R_BIT 1
+
+#define FD_EV_ACTIVE_W_BIT 4
#define FD_EV_READY_W_BIT 5
#define FD_EV_STATUS (FD_EV_ACTIVE | FD_EV_READY)