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, 6 insertions, 3 deletions

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index b423965a78d1..c600954998d5 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -425,16 +425,17 @@ static void slc_setup(struct net_device *dev)
  * in parallel
  */
 
-static void slcan_receive_buf(struct tty_struct *tty,
+static unsigned int slcan_receive_buf(struct tty_struct *tty,
                               const unsigned char *cp, char *fp, int count)
 {
         struct slcan *sl = (struct slcan *) tty->disc_data;
+        int bytes = count;
 
         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
-                return;
+                return -ENODEV;
 
         /* Read the characters out of the buffer */
-        while (count--) {
+        while (bytes--) {
                 if (fp && *fp++) {
                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
                                 sl->dev->stats.rx_errors++;
@@ -443,6 +444,8 @@ static void slcan_receive_buf(struct tty_struct *tty,
                 }
                 slcan_unesc(sl, *cp++);
         }
+
+        return count;
 }
 
 /************************************