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/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 47f8cdb207f1..6abc73598847 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2138,8 +2138,8 @@ static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
         gsm->tty = NULL;
 }
 
-static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
-                              char *fp, int count)
+static unsigned int gsmld_receive_buf(struct tty_struct *tty,
+                const unsigned char *cp, char *fp, int count)
 {
         struct gsm_mux *gsm = tty->disc_data;
         const unsigned char *dp;
@@ -2173,6 +2173,8 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
         }
         /* FASYNC if needed ? */
         /* If clogged call tty_throttle(tty); */
+
+        return count;
 }
 
 /**