tty: make receive_buf() return the amout of bytes received

it makes it simpler to keep track of the amount of
bytes received and simplifies how flush_to_ldisc counts
the remaining bytes. It also fixes a bug of lost bytes
on n_tty when flushing too many bytes via the USB
serial gadget driver.

Tested-by: Stefan Bigler <stefan.bigler@keymile.com>
Tested-by: Toby Gray <toby.gray@realvnc.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/net/ppp_synctty.c b/drivers/net/ppp_synctty.c
index 2573f525f11c..0815790a5cf9 100644
--- a/drivers/net/ppp_synctty.c
+++ b/drivers/net/ppp_synctty.c
@@ -381,7 +381,7 @@ ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
 }
 
 /* May sleep, don't call from interrupt level or with interrupts disabled */
-static void
+static unsigned int
 ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
                   char *cflags, int count)
 {
@@ -389,7 +389,7 @@ ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
         unsigned long flags;
 
         if (!ap)
-                return;
+                return -ENODEV;
         spin_lock_irqsave(&ap->recv_lock, flags);
         ppp_sync_input(ap, buf, cflags, count);
         spin_unlock_irqrestore(&ap->recv_lock, flags);
@@ -397,6 +397,8 @@ ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
                 tasklet_schedule(&ap->tsk);
         sp_put(ap);
         tty_unthrottle(tty);
+
+        return count;
 }
 
 static void