netif: document feature-split-event-channel

This is a new feature to separate TX and RX notification. Document it in
canonical header for future reference.

For reference implementation, please see Xen network driver in Linux kernel.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
index 9664998f05cb3e08e5948112f868ff085000bd05..d477751d7355d75b95099bc825742775b411e928 100644 (file)
--- a/xen/include/public/io/netif.h
+++ b/xen/include/public/io/netif.h
@@ -56,6 +56,18 @@
  * that it cannot safely queue packets (as it may not be kicked to send them).
  */
 
+/*
+ * "feature-split-event-channels" is introduced to separate guest TX
+ * and RX notification. Backend either doesn't support this feature or
+ * advertises it via xenstore as 0 (disabled) or 1 (enabled).
+ *
+ * To make use of this feature, frontend should allocate two event
+ * channels for TX and RX, advertise them to backend as
+ * "event-channel-tx" and "event-channel-rx" respectively. If frontend
+ * doesn't want to use this feature, it just writes "event-channel"
+ * node as before.
+ */
+
 /*
  * This is the 'wire' format for packets:
  *  Request 1: netif_tx_request -- NETTXF_* (any flags)