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>

6 files changed, 44 insertions, 69 deletions

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 47f8cdb207f..6abc7359884 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2138,8 +2138,8 @@ static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
         gsm->tty = NULL;
 }
 
-static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
-                              char *fp, int count)
+static unsigned int gsmld_receive_buf(struct tty_struct *tty,
+                const unsigned char *cp, char *fp, int count)
 {
         struct gsm_mux *gsm = tty->disc_data;
         const unsigned char *dp;
@@ -2173,6 +2173,8 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
         }
         /* FASYNC if needed ? */
         /* If clogged call tty_throttle(tty); */
+
+        return count;
 }
 
 /**
diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
index cea56033b34..cac666314ae 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() */
 
 /**
diff --git a/drivers/tty/n_r3964.c b/drivers/tty/n_r3964.c
index 5c6c31459a2..a4bc39c21a4 100644
--- a/drivers/tty/n_r3964.c
+++ b/drivers/tty/n_r3964.c
@@ -139,8 +139,8 @@ static int r3964_ioctl(struct tty_struct *tty, struct file *file,
 static void r3964_set_termios(struct tty_struct *tty, struct ktermios *old);
 static unsigned int r3964_poll(struct tty_struct *tty, struct file *file,
                 struct poll_table_struct *wait);
-static void r3964_receive_buf(struct tty_struct *tty, const unsigned char *cp,
-                char *fp, int count);
+static unsigned int r3964_receive_buf(struct tty_struct *tty,
+                const unsigned char *cp, char *fp, int count);
 
 static struct tty_ldisc_ops tty_ldisc_N_R3964 = {
         .owner = THIS_MODULE,
@@ -1239,8 +1239,8 @@ static unsigned int r3964_poll(struct tty_struct *tty, struct file *file,
         return result;
 }
 
-static void r3964_receive_buf(struct tty_struct *tty, const unsigned char *cp,
-                        char *fp, int count)
+static unsigned int r3964_receive_buf(struct tty_struct *tty,
+                const unsigned char *cp, char *fp, int count)
 {
         struct r3964_info *pInfo = tty->disc_data;
         const unsigned char *p;
@@ -1257,6 +1257,8 @@ static void r3964_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                 }
 
         }
+
+        return count;
 }
 
 MODULE_LICENSE("GPL");
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 0ad32888091..95d0a9c2dd1 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -81,38 +81,6 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
         return put_user(x, ptr);
 }
 
-/**
- *      n_tty_set__room -       receive space
- *      @tty: terminal
- *
- *      Called by the driver to find out how much data it is
- *      permitted to feed to the line discipline without any being lost
- *      and thus to manage flow control. Not serialized. Answers for the
- *      "instant".
- */
-
-static void n_tty_set_room(struct tty_struct *tty)
-{
-        /* tty->read_cnt is not read locked ? */
-        int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
-        int old_left;
-
-        /*
-         * If we are doing input canonicalization, and there are no
-         * pending newlines, let characters through without limit, so
-         * that erase characters will be handled.  Other excess
-         * characters will be beeped.
-         */
-        if (left <= 0)
-                left = tty->icanon && !tty->canon_data;
-        old_left = tty->receive_room;
-        tty->receive_room = left;
-
-        /* Did this open up the receive buffer? We may need to flip */
-        if (left && !old_left)
-                schedule_work(&tty->buf.work);
-}
-
 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
 {
         if (tty->read_cnt < N_TTY_BUF_SIZE) {
@@ -184,7 +152,6 @@ static void reset_buffer_flags(struct tty_struct *tty)
 
         tty->canon_head = tty->canon_data = tty->erasing = 0;
         memset(&tty->read_flags, 0, sizeof tty->read_flags);
-        n_tty_set_room(tty);
         check_unthrottle(tty);
 }
 
@@ -1360,17 +1327,19 @@ static void n_tty_write_wakeup(struct tty_struct *tty)
  *      calls one at a time and in order (or using flush_to_ldisc)
  */
 
-static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
-                              char *fp, int count)
+static unsigned int n_tty_receive_buf(struct tty_struct *tty,
+                const unsigned char *cp, char *fp, int count)
 {
         const unsigned char *p;
         char *f, flags = TTY_NORMAL;
         int     i;
         char    buf[64];
         unsigned long cpuflags;
+        int left;
+        int ret = 0;
 
         if (!tty->read_buf)
-                return;
+                return 0;
 
         if (tty->real_raw) {
                 spin_lock_irqsave(&tty->read_lock, cpuflags);
@@ -1380,6 +1349,7 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                 memcpy(tty->read_buf + tty->read_head, cp, i);
                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
                 tty->read_cnt += i;
+                ret += i;
                 cp += i;
                 count -= i;
 
@@ -1389,8 +1359,10 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                 memcpy(tty->read_buf + tty->read_head, cp, i);
                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
                 tty->read_cnt += i;
+                ret += i;
                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
         } else {
+                ret = count;
                 for (i = count, p = cp, f = fp; i; i--, p++) {
                         if (f)
                                 flags = *f++;
@@ -1418,8 +1390,6 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                         tty->ops->flush_chars(tty);
         }
 
-        n_tty_set_room(tty);
-
         if ((!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) ||
                 L_EXTPROC(tty)) {
                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
@@ -1432,8 +1402,12 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
          * mode.  We don't want to throttle the driver if we're in
          * canonical mode and don't have a newline yet!
          */
-        if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
+        left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
+
+        if (left < TTY_THRESHOLD_THROTTLE)
                 tty_throttle(tty);
+
+        return ret;
 }
 
 int is_ignored(int sig)
@@ -1477,7 +1451,6 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
                 tty->raw = 1;
                 tty->real_raw = 1;
-                n_tty_set_room(tty);
                 return;
         }
         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
@@ -1530,7 +1503,6 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
                 else
                         tty->real_raw = 0;
         }
-        n_tty_set_room(tty);
         /* The termios change make the tty ready for I/O */
         wake_up_interruptible(&tty->write_wait);
         wake_up_interruptible(&tty->read_wait);
@@ -1812,8 +1784,6 @@ do_it_again:
                                 retval = -ERESTARTSYS;
                                 break;
                         }
-                        /* FIXME: does n_tty_set_room need locking ? */
-                        n_tty_set_room(tty);
                         timeout = schedule_timeout(timeout);
                         continue;
                 }
@@ -1885,10 +1855,8 @@ do_it_again:
                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
                  * we won't get any more characters.
                  */
-                if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
-                        n_tty_set_room(tty);
+                if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE)
                         check_unthrottle(tty);
-                }
 
                 if (b - buf >= minimum)
                         break;
@@ -1910,7 +1878,6 @@ do_it_again:
         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
                  goto do_it_again;
 
-        n_tty_set_room(tty);
         return retval;
 }
 
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index f1a7918d71a..46de2e075da 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -416,6 +416,7 @@ static void flush_to_ldisc(struct work_struct *work)
                 struct tty_buffer *head, *tail = tty->buf.tail;
                 int seen_tail = 0;
                 while ((head = tty->buf.head) != NULL) {
+                        int copied;
                         int count;
                         char *char_buf;
                         unsigned char *flag_buf;
@@ -442,17 +443,19 @@ static void flush_to_ldisc(struct work_struct *work)
                            line discipline as we want to empty the queue */
                         if (test_bit(TTY_FLUSHPENDING, &tty->flags))
                                 break;
-                        if (!tty->receive_room || seen_tail)
-                                break;
-                        if (count > tty->receive_room)
-                                count = tty->receive_room;
                         char_buf = head->char_buf_ptr + head->read;
                         flag_buf = head->flag_buf_ptr + head->read;
-                        head->read += count;
                         spin_unlock_irqrestore(&tty->buf.lock, flags);
-                        disc->ops->receive_buf(tty, char_buf,
+                        copied = disc->ops->receive_buf(tty, char_buf,
                                                         flag_buf, count);
                         spin_lock_irqsave(&tty->buf.lock, flags);
+
+                        head->read += copied;
+
+                        if (copied == 0 || seen_tail) {
+                                schedule_work(&tty->buf.work);
+                                break;
+                        }
                 }
                 clear_bit(TTY_FLUSHING, &tty->flags);
         }
diff --git a/drivers/tty/vt/selection.c b/drivers/tty/vt/selection.c
index fb864e7fcd1..67b1d0d7c8a 100644
--- a/drivers/tty/vt/selection.c
+++ b/drivers/tty/vt/selection.c
@@ -332,8 +332,7 @@ int paste_selection(struct tty_struct *tty)
                         continue;
                 }
                 count = sel_buffer_lth - pasted;
-                count = min(count, tty->receive_room);
-                tty->ldisc->ops->receive_buf(tty, sel_buffer + pasted,
+                count = tty->ldisc->ops->receive_buf(tty, sel_buffer + pasted,
                                                                 NULL, count);
                 pasted += count;
         }