We check for -EAGAIN in n_tty_write() but never currently get it from
process_output_block(). Let's add -EAGAIN handling and break out with 0
bytes processed. Note that if we return -EAGAIN from n_tty_write(), it
will be treated as error by the caller rather than a retry.
Looking at the patch description for commit 9ef8927f45f2 ("n_tty: check
for negative and zero space return from tty_write_room") it looks like we
have not made use of -EGAIN from process_output_block() so far, so this
does not seem like it's currently needed as a fix.
We can use -EAGAIN for serial layer power management changes as we now
will make use of write_room() returning 0 for an idled serial port.
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
---
drivers/tty/n_tty.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -549,6 +549,8 @@ static ssize_t process_output_block(struct tty_struct *tty,
space = tty_write_room(tty);
if (space <= 0) {
mutex_unlock(&ldata->output_lock);
+ if (!space)
+ space = -EAGAIN;
return space;
}
if (nr > space)
@@ -2287,8 +2289,10 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
while (nr > 0) {
ssize_t num = process_output_block(tty, b, nr);
if (num < 0) {
- if (num == -EAGAIN)
- break;
+ if (num == -EAGAIN) {
+ retval = 0;
+ goto break_out;
+ }
retval = num;
goto break_out;
}
--
2.33.0
