tty: Enable configurable tty flip buffer limit

Allow driver to configure its maximum flip buffer memory
consumption/limit. This is necessary for very-high speed line
rates (in excess of 10MB/sec) because the flip buffers can
be saturated before the line discipline has a chance to
throttle the input.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 97d660ed70c1..2225745060d6 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -61,6 +61,7 @@ struct tty_bufhead {
         struct tty_buffer sentinel;
         struct llist_head free;         /* Free queue head */
         atomic_t           memory_used; /* In-use buffers excluding free list */
+        int                mem_limit;
         struct tty_buffer *tail;        /* Active buffer */
 };
 /*
diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h
index 21ddd7d9ea1f..2da8bc2a5486 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -1,6 +1,7 @@
 #ifndef _LINUX_TTY_FLIP_H
 #define _LINUX_TTY_FLIP_H
 
+extern int tty_buffer_set_limit(struct tty_port *port, int limit);
 extern int tty_buffer_space_avail(struct tty_port *port);
 extern int tty_buffer_request_room(struct tty_port *port, size_t size);
 extern int tty_insert_flip_string_flags(struct tty_port *port,