[PATCH 7/9] n_tty: Only flush echo output if actually output

From: Peter Hurley
Date: Mon Apr 15 2013 - 11:31:46 EST


Don't have the driver flush received echoes if no echoes were
actually output.

Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_tty.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 6f507f5..a601c46 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -645,14 +645,14 @@ break_out:
* Locking: callers must hold output_lock
*/

-static void __process_echoes(struct tty_struct *tty)
+static size_t __process_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
- int space, nr;
+ int space, old_space;
size_t tail;
unsigned char c;

- space = tty_write_room(tty);
+ old_space = space = tty_write_room(tty);

tail = ldata->echo_tail;
nr = ldata->echo_commit - ldata->echo_tail;
@@ -785,12 +785,13 @@ static void __process_echoes(struct tty_struct *tty)
}

ldata->echo_tail = tail;
+ return old_space - space;
}

static void commit_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
- size_t nr, old;
+ size_t nr, old, echoed;
size_t head;

head = ldata->echo_head;
@@ -805,25 +806,26 @@ static void commit_echoes(struct tty_struct *tty)

mutex_lock(&ldata->output_lock);
ldata->echo_commit = head;
- __process_echoes(tty);
+ echoed = __process_echoes(tty);
mutex_unlock(&ldata->output_lock);

- if (tty->ops->flush_chars)
+ if (echoed && tty->ops->flush_chars)
tty->ops->flush_chars(tty);
}

static void process_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
+ size_t echoed;

if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)
return;

mutex_lock(&ldata->output_lock);
- __process_echoes(tty);
+ echoed = __process_echoes(tty);
mutex_unlock(&ldata->output_lock);

- if (tty->ops->flush_chars)
+ if (echoed && tty->ops->flush_chars)
tty->ops->flush_chars(tty);
}

--
1.8.1.2

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