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, 10 insertions, 8 deletions

diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
index cea56033b34c..cac666314aef 100644
--- a/drivers/tty/n_hdlc.c
+++ b/drivers/tty/n_hdlc.c
@@ -188,8 +188,8 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
                                     poll_table *wait);
 static int n_hdlc_tty_open(struct tty_struct *tty);
 static void n_hdlc_tty_close(struct tty_struct *tty);
-static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
-                               char *fp, int count);
+static unsigned int n_hdlc_tty_receive(struct tty_struct *tty,
+                const __u8 *cp, char *fp, int count);
 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 
 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
@@ -509,8 +509,8 @@ static void n_hdlc_tty_wakeup(struct tty_struct *tty)
  * Called by tty low level driver when receive data is available. Data is
  * interpreted as one HDLC frame.
  */
-static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
-                               char *flags, int count)
+static unsigned int n_hdlc_tty_receive(struct tty_struct *tty,
+                const __u8 *data, char *flags, int count)
 {
         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
         register struct n_hdlc_buf *buf;
@@ -521,20 +521,20 @@ static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
                 
         /* This can happen if stuff comes in on the backup tty */
         if (!n_hdlc || tty != n_hdlc->tty)
-                return;
+                return -ENODEV;
                 
         /* verify line is using HDLC discipline */
         if (n_hdlc->magic != HDLC_MAGIC) {
                 printk("%s(%d) line not using HDLC discipline\n",
                         __FILE__,__LINE__);
-                return;
+                return -EINVAL;
         }
         
         if ( count>maxframe ) {
                 if (debuglevel >= DEBUG_LEVEL_INFO)     
                         printk("%s(%d) rx count>maxframesize, data discarded\n",
                                __FILE__,__LINE__);
-                return;
+                return -EINVAL;
         }
 
         /* get a free HDLC buffer */    
@@ -550,7 +550,7 @@ static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
                 if (debuglevel >= DEBUG_LEVEL_INFO)     
                         printk("%s(%d) no more rx buffers, data discarded\n",
                                __FILE__,__LINE__);
-                return;
+                return -EINVAL;
         }
                 
         /* copy received data to HDLC buffer */
@@ -565,6 +565,8 @@ static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
         if (n_hdlc->tty->fasync != NULL)
                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
 
+        return count;
+
 }       /* end of n_hdlc_tty_receive() */
 
 /**