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, 5 insertions, 3 deletions

diff --git a/drivers/isdn/gigaset/ser-gigaset.c b/drivers/isdn/gigaset/ser-gigaset.c
index 86a5c4f7775e..1d44d470897c 100644
--- a/drivers/isdn/gigaset/ser-gigaset.c
+++ b/drivers/isdn/gigaset/ser-gigaset.c
@@ -674,7 +674,7 @@ gigaset_tty_ioctl(struct tty_struct *tty, struct file *file,
  *      cflags  buffer containing error flags for received characters (ignored)
  *      count   number of received characters
  */
-static void
+static unsigned int
 gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf,
                     char *cflags, int count)
 {
@@ -683,12 +683,12 @@ gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf,
         struct inbuf_t *inbuf;
 
         if (!cs)
-                return;
+                return -ENODEV;
         inbuf = cs->inbuf;
         if (!inbuf) {
                 dev_err(cs->dev, "%s: no inbuf\n", __func__);
                 cs_put(cs);
-                return;
+                return -EINVAL;
         }
 
         tail = inbuf->tail;
@@ -725,6 +725,8 @@ gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf,
         gig_dbg(DEBUG_INTR, "%s-->BH", __func__);
         gigaset_schedule_event(cs);
         cs_put(cs);
+
+        return count;
 }
 
 /*