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/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index 3df0c0f8b8bf..73c7e03617ec 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -167,8 +167,8 @@ static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 
 #endif
 
-static void ldisc_receive(struct tty_struct *tty, const u8 *data,
-                        char *flags, int count)
+static unsigned int ldisc_receive(struct tty_struct *tty,
+                const u8 *data, char *flags, int count)
 {
         struct sk_buff *skb = NULL;
         struct ser_device *ser;
@@ -215,6 +215,8 @@ static void ldisc_receive(struct tty_struct *tty, const u8 *data,
         } else
                 ++ser->dev->stats.rx_dropped;
         update_tty_status(ser);
+
+        return count;
 }
 
 static int handle_tx(struct ser_device *ser)