termios: document callback more clearly
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/tty.txt b/Documentation/tty.txt
index 048a876..8e65c44 100644
--- a/Documentation/tty.txt
+++ b/Documentation/tty.txt
@@ -132,6 +132,14 @@
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
