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authorPeter Hurley <peter@hurleysoftware.com>2013-11-22 12:09:55 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-08 16:57:38 -0800
commit4d18e6eff81e1d4d81d0942d5b7e96904b3b32df (patch)
treea6c66c84189a50bff8b6b05a7187a8cda4b67cfc /drivers/tty/tty_buffer.c
parent82f91fe092b6eacd82e976b8955443f9fd97d07e (diff)
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>
Diffstat (limited to 'drivers/tty/tty_buffer.c')
-rw-r--r--drivers/tty/tty_buffer.c24
1 files changed, 21 insertions, 3 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index c043136fbe51..57eb34b2ec24 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -26,7 +26,7 @@
* Byte threshold to limit memory consumption for flip buffers.
* The actual memory limit is > 2x this amount.
*/
-#define TTYB_MEM_LIMIT 65536
+#define TTYB_DEFAULT_MEM_LIMIT 65536
/*
* We default to dicing tty buffer allocations to this many characters
@@ -89,7 +89,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port)
int tty_buffer_space_avail(struct tty_port *port)
{
- int space = TTYB_MEM_LIMIT - atomic_read(&port->buf.memory_used);
+ int space = port->buf.mem_limit - atomic_read(&port->buf.memory_used);
return max(space, 0);
}
@@ -162,7 +162,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
/* Should possibly check if this fails for the largest buffer we
have queued and recycle that ? */
- if (atomic_read(&port->buf.memory_used) > TTYB_MEM_LIMIT)
+ if (atomic_read(&port->buf.memory_used) > port->buf.mem_limit)
return NULL;
p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
if (p == NULL)
@@ -536,4 +536,22 @@ void tty_buffer_init(struct tty_port *port)
atomic_set(&buf->memory_used, 0);
atomic_set(&buf->priority, 0);
INIT_WORK(&buf->work, flush_to_ldisc);
+ buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
}
+
+/**
+ * tty_buffer_set_limit - change the tty buffer memory limit
+ * @port: tty port to change
+ *
+ * Change the tty buffer memory limit.
+ * Must be called before the other tty buffer functions are used.
+ */
+
+int tty_buffer_set_limit(struct tty_port *port, int limit)
+{
+ if (limit < MIN_TTYB_SIZE)
+ return -EINVAL;
+ port->buf.mem_limit = limit;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tty_buffer_set_limit);