POLL_OUT in ttys, misc bug fix

@@ -5,6 +5,10 @@
  *
  *  Added support for a Unix98-style ptmx device.
  *    -- C. Scott Ananian <[email protected]>, 14-Jan-1998
+ *  Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to
+ *      waiting writers -- Sapan Bhatia <[email protected]>
+ *
+ *
  */
 
 #include <linux/config.h>

@@ -331,6 +335,8 @@
 	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 	wake_up_interruptible(&pty->open_wait);
 	set_bit(TTY_THROTTLED, &tty->flags);
+	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+
 	/*  Register a slave for the master  */
 	if (tty->driver.major == PTY_MASTER_MAJOR)
 		tty_register_devfs(&tty->link->driver,

@@ -23,6 +23,13 @@
  * 2000/01/20   Fixed SMP locking on put_tty_queue using bits of 
  *		the patch by Andrew J. Kroll <[email protected]>
  *		who actually finally proved there really was a race.
+ *
+ * 2002/03/18   Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
+ *		waiting writing processes-Sapan Bhatia <[email protected]>
+ *
+ * 2002/03/19   Fixed write_chan to stay put if console driver returns
+ *              EAGAIN and not return since it returns an EAGAIN in a 
+ *		non-blocking operation-Sapan Bhatia <[email protected]>
  */
 
 #include <linux/types.h>

@@ -711,6 +718,22 @@
 	return 0;
 }
 
+/*
+ * Required for the ptys, serial driver etc. since processes
+ * that attach themselves to the master and rely on ASYNC
+ * IO must be woken up
+ */
+
+static void n_tty_write_wakeup(struct tty_struct *tty)
+{
+	if (tty->fasync)
+	{
+ 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+		kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
+	}
+	return;
+}
+
 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 			      char *fp, int count)
 {

@@ -1156,7 +1179,7 @@
 		if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
 			while (nr > 0) {
 				ssize_t num = opost_block(tty, b, nr);
-				if (num < 0) {
+				if (num < 0 && num != -EAGAIN) {
 					retval = num;
 					goto break_out;
 				}

@@ -1236,6 +1259,6 @@
 	normal_poll,		/* poll */
 	n_tty_receive_buf,	/* receive_buf */
 	n_tty_receive_room,	/* receive_room */
-	0			/* write_wakeup */
+	n_tty_write_wakeup	/* write_wakeup */
 };