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, 7 insertions, 4 deletions

diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c
index 4c628393c8b1..0e4f23531140 100644
--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -923,13 +923,14 @@ static long mkiss_compat_ioctl(struct tty_struct *tty, struct file *file,
  * a block of data has been received, which can now be decapsulated
  * and sent on to the AX.25 layer for further processing.
  */
-static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
-        char *fp, int count)
+static unsigned int mkiss_receive_buf(struct tty_struct *tty,
+                const unsigned char *cp, char *fp, int count)
 {
         struct mkiss *ax = mkiss_get(tty);
+        int bytes = count;
 
         if (!ax)
-                return;
+                return -ENODEV;
 
         /*
          * Argh! mtu change time! - costs us the packet part received
@@ -939,7 +940,7 @@ static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                 ax_changedmtu(ax);
 
         /* Read the characters out of the buffer */
-        while (count--) {
+        while (bytes--) {
                 if (fp != NULL && *fp++) {
                         if (!test_and_set_bit(AXF_ERROR, &ax->flags))
                                 ax->dev->stats.rx_errors++;
@@ -952,6 +953,8 @@ static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 
         mkiss_put(ax);
         tty_unthrottle(tty);
+
+        return count;
 }
 
 /*