n_hdlc: honor O_NONBLOCK on write

Make n_hdlc line discipline honor the O_NONBLOCK file flag on write.

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c
index ed4e03333ab4..69ec6399c714 100644
--- a/drivers/char/n_hdlc.c
+++ b/drivers/char/n_hdlc.c
@@ -677,6 +677,10 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
         /* Allocate transmit buffer */
         /* sleep until transmit buffer available */             
         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
+                if (file->f_flags & O_NONBLOCK) {
+                        error = -EAGAIN;
+                        break;
+                }
                 schedule();
                         
                 n_hdlc = tty2n_hdlc (tty);