tty: Introduce a tty_port generic block_til_ready

Start sucking more commonality out of the drivers into a single piece of
core code.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 105 insertions, 0 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 9f418bca4a2..ff94182b381 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -151,3 +151,108 @@ void tty_port_raise_dtr_rts(struct tty_port *port)
 		port->ops->raise_dtr_rts(port);
 }
 EXPORT_SYMBOL(tty_port_raise_dtr_rts);
+
+/**
+ *	tty_port_block_til_ready	-	Waiting logic for tty open
+ *	@port: the tty port being opened
+ *	@tty: the tty device being bound
+ *	@filp: the file pointer of the opener
+ *
+ *	Implement the core POSIX/SuS tty behaviour when opening a tty device.
+ *	Handles:
+ *		- hangup (both before and during)
+ *		- non blocking open
+ *		- rts/dtr/dcd
+ *		- signals
+ *		- port flags and counts
+ *
+ *	The passed tty_port must implement the carrier_raised method if it can
+ *	do carrier detect and the raise_dtr_rts method if it supports software
+ *	management of these lines. Note that the dtr/rts raise is done each
+ *	iteration as a hangup may have previously dropped them while we wait.
+ */
+ 
+int tty_port_block_til_ready(struct tty_port *port,
+				struct tty_struct *tty, struct file *filp)
+{
+	int do_clocal = 0, retval;
+	unsigned long flags;
+	DECLARE_WAITQUEUE(wait, current);
+	int cd;
+
+	/* block if port is in the process of being closed */
+	if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
+		interruptible_sleep_on(&port->close_wait);
+		if (port->flags & ASYNC_HUP_NOTIFY)
+			return -EAGAIN;
+		else
+			return -ERESTARTSYS;
+	}
+
+	/* if non-blocking mode is set we can pass directly to open unless
+	   the port has just hung up or is in another error state */
+	if ((filp->f_flags & O_NONBLOCK) ||
+			(tty->flags & (1 << TTY_IO_ERROR))) {
+		port->flags |= ASYNC_NORMAL_ACTIVE;
+		return 0;
+	}
+
+	if (C_CLOCAL(tty))
+		do_clocal = 1;
+
+	/* Block waiting until we can proceed. We may need to wait for the
+	   carrier, but we must also wait for any close that is in progress
+	   before the next open may complete */
+
+	retval = 0;
+	add_wait_queue(&port->open_wait, &wait);
+
+	/* The port lock protects the port counts */
+	spin_lock_irqsave(&port->lock, flags);
+	if (!tty_hung_up_p(filp))
+		port->count--;
+	port->blocked_open++;
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	while (1) {
+		/* Indicate we are open */
+		tty_port_raise_dtr_rts(port);
+
+		set_current_state(TASK_INTERRUPTIBLE);
+		/* Check for a hangup or uninitialised port. Return accordingly */
+		if (tty_hung_up_p(filp) || !(port->flags & ASYNC_INITIALIZED)) {
+			if (port->flags & ASYNC_HUP_NOTIFY)
+				retval = -EAGAIN;
+			else
+				retval = -ERESTARTSYS;
+			break;
+		}
+		/* Probe the carrier. For devices with no carrier detect this
+		   will always return true */
+		cd = tty_port_carrier_raised(port);
+		if (!(port->flags & ASYNC_CLOSING) &&
+				(do_clocal || cd))
+			break;
+		if (signal_pending(current)) {
+			retval = -ERESTARTSYS;
+			break;
+		}
+		schedule();
+	}
+	set_current_state(TASK_RUNNING);
+	remove_wait_queue(&port->open_wait, &wait);
+
+	/* Update counts. A parallel hangup will have set count to zero and
+	   we must not mess that up further */
+	spin_lock_irqsave(&port->lock, flags);
+	if (!tty_hung_up_p(filp))
+		port->count++;
+	port->blocked_open--;
+	if (retval == 0)
+		port->flags |= ASYNC_NORMAL_ACTIVE;
+	spin_unlock_irqrestore(&port->lock, flags);
+	return 0;
+	
+}
+EXPORT_SYMBOL(tty_port_block_til_ready);
+