tty: Clarify documentation of ->write()

The tty driver write method is different to the usual fops device write
methods as the buffer is already in kernel space. Clarify the docs since
someone writing a driver made that mistake.

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 5f799e612e039f19f530090cd01161fdfc12c1ca..048a8762cfb548fbe2b2078ea8527a7a9c50bc01 100644 (file)
--- a/Documentation/tty.txt
+++ b/Documentation/tty.txt
@@ -108,7 +108,9 @@ hardware driver through the function pointers within the tty->driver
 structure:
 
 write()                        Write a block of characters to the tty device.
-                       Returns the number of characters accepted.
+                       Returns the number of characters accepted. The
+                       character buffer passed to this method is already
+                       in kernel space.
 
 put_char()             Queues a character for writing to the tty device.
                        If there is no room in the queue, the character is