X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=Documentation%2Ftty.txt;h=8e65c4498c521259d93061e0a94a2d3652eaef98;hb=5f0547c2813d4677908fa6de02f9911d25996515;hp=048a8762cfb548fbe2b2078ea8527a7a9c50bc01;hpb=8269cc4e2b0ddcdcb9e7f2034c464ef8613737a1;p=firefly-linux-kernel-4.4.55.git

diff --git a/Documentation/tty.txt b/Documentation/tty.txt
index 048a8762cfb5..8e65c4498c52 100644
--- a/Documentation/tty.txt
+++ b/Documentation/tty.txt
@@ -132,6 +132,14 @@ set_termios()		Notify the tty driver that the device's termios
 			tty->termios. Previous settings should be passed in
 			the "old" argument.
 
+			The API is defined such that the driver should return
+			the actual modes selected. This means that the
+			driver function is responsible for modifying any
+			bits in the request it cannot fulfill to indicate
+			the actual modes being used. A device with no
+			hardware capability for change (eg a USB dongle or
+			virtual port) can provide NULL for this method.
+
 throttle()		Notify the tty driver that input buffers for the
 			line discipline are close to full, and it should
 			somehow signal that no more characters should be