Merge tag 'tty-4.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial updates from Greg KH:
 "Here's the big tty/serial driver pull request for 4.6-rc1.

  Lots of changes in here, Peter has been on a tear again, with lots of
  refactoring and bugs fixes, many thanks to the great work he has been
  doing.  Lots of driver updates and fixes as well, full details in the
  shortlog.

  All have been in linux-next for a while with no reported issues"

* tag 'tty-4.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (220 commits)
  serial: 8250: describe CONFIG_SERIAL_8250_RSA
  serial: samsung: optimize UART rx fifo access routine
  serial: pl011: add mark/space parity support
  serial: sa1100: make sa1100_register_uart_fns a function
  tty: serial: 8250: add MOXA Smartio MUE boards support
  serial: 8250: convert drivers to use up_to_u8250p()
  serial: 8250/mediatek: fix building with SERIAL_8250=m
  serial: 8250/ingenic: fix building with SERIAL_8250=m
  serial: 8250/uniphier: fix modular build
  Revert "drivers/tty/serial: make 8250/8250_ingenic.c explicitly non-modular"
  Revert "drivers/tty/serial: make 8250/8250_mtk.c explicitly non-modular"
  serial: mvebu-uart: initial support for Armada-3700 serial port
  serial: mctrl_gpio: Add missing module license
  serial: ifx6x60: avoid uninitialized variable use
  tty/serial: at91: fix bad offset for UART timeout register
  tty/serial: at91: restore dynamic driver binding
  serial: 8250: Add hardware dependency to RT288X option
  TTY, devpts: document pty count limiting
  tty: goldfish: support platform_device with id -1
  drivers: tty: goldfish: Add device tree bindings
  ...

1 files changed, 104 insertions, 94 deletions

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index a054d03c22e7..68947f6de5ad 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -140,9 +140,16 @@ static void put_ldops(struct tty_ldisc_ops *ldops)
  *	@disc: ldisc number
  *
  *	Takes a reference to a line discipline. Deals with refcounts and
- *	module locking counts. Returns NULL if the discipline is not available.
- *	Returns a pointer to the discipline and bumps the ref count if it is
- *	available
+ *	module locking counts.
+ *
+ *	Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or
+ *			 if the discipline is not registered
+ *		 -EAGAIN if request_module() failed to load or register the
+ *			 the discipline
+ *		 -ENOMEM if allocation failure
+ *
+ *		 Otherwise, returns a pointer to the discipline and bumps the
+ *		 ref count
  *
  *	Locking:
  *		takes tty_ldiscs_lock to guard against ldisc races
@@ -250,19 +257,23 @@ const struct file_operations tty_ldiscs_proc_fops = {
  *	reference to it. If the line discipline is in flux then
  *	wait patiently until it changes.
  *
+ *	Returns: NULL if the tty has been hungup and not re-opened with
+ *		 a new file descriptor, otherwise valid ldisc reference
+ *
  *	Note: Must not be called from an IRQ/timer context. The caller
  *	must also be careful not to hold other locks that will deadlock
  *	against a discipline change, such as an existing ldisc reference
  *	(which we check for)
  *
- *	Note: only callable from a file_operations routine (which
- *	guarantees tty->ldisc != NULL when the lock is acquired).
+ *	Note: a file_operations routine (read/poll/write) should use this
+ *	function to wait for any ldisc lifetime events to finish.
  */
 
 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
 {
 	ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);
-	WARN_ON(!tty->ldisc);
+	if (!tty->ldisc)
+		ldsem_up_read(&tty->ldisc_sem);
 	return tty->ldisc;
 }
 EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
@@ -304,13 +315,13 @@ void tty_ldisc_deref(struct tty_ldisc *ld)
 EXPORT_SYMBOL_GPL(tty_ldisc_deref);
 
 
-static inline int __lockfunc
+static inline int
 __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
 {
 	return ldsem_down_write(&tty->ldisc_sem, timeout);
 }
 
-static inline int __lockfunc
+static inline int
 __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout)
 {
 	return ldsem_down_write_nested(&tty->ldisc_sem,
@@ -322,8 +333,7 @@ static inline void __tty_ldisc_unlock(struct tty_struct *tty)
 	ldsem_up_write(&tty->ldisc_sem);
 }
 
-static int __lockfunc
-tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
+static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
 {
 	int ret;
 
@@ -340,7 +350,7 @@ static void tty_ldisc_unlock(struct tty_struct *tty)
 	__tty_ldisc_unlock(tty);
 }
 
-static int __lockfunc
+static int
 tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
 			    unsigned long timeout)
 {
@@ -376,14 +386,13 @@ tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
 	return 0;
 }
 
-static void __lockfunc
-tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
+static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
 {
 	tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
 }
 
-static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty,
-					     struct tty_struct *tty2)
+static void tty_ldisc_unlock_pair(struct tty_struct *tty,
+				  struct tty_struct *tty2)
 {
 	__tty_ldisc_unlock(tty);
 	if (tty2)
@@ -411,7 +420,7 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush);
 /**
  *	tty_set_termios_ldisc		-	set ldisc field
  *	@tty: tty structure
- *	@num: line discipline number
+ *	@disc: line discipline number
  *
  *	This is probably overkill for real world processors but
  *	they are not on hot paths so a little discipline won't do
@@ -424,10 +433,10 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush);
  *	Locking: takes termios_rwsem
  */
 
-static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
+static void tty_set_termios_ldisc(struct tty_struct *tty, int disc)
 {
 	down_write(&tty->termios_rwsem);
-	tty->termios.c_line = num;
+	tty->termios.c_line = disc;
 	up_write(&tty->termios_rwsem);
 
 	tty->disc_data = NULL;
@@ -455,7 +464,7 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
 		if (ret)
 			clear_bit(TTY_LDISC_OPEN, &tty->flags);
 
-		tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc);
+		tty_ldisc_debug(tty, "%p: opened\n", ld);
 		return ret;
 	}
 	return 0;
@@ -476,7 +485,7 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
 	clear_bit(TTY_LDISC_OPEN, &tty->flags);
 	if (ld->ops->close)
 		ld->ops->close(tty);
-	tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc);
+	tty_ldisc_debug(tty, "%p: closed\n", ld);
 }
 
 /**
@@ -525,12 +534,12 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
  *	the close of one side of a tty/pty pair, and eventually hangup.
  */
 
-int tty_set_ldisc(struct tty_struct *tty, int ldisc)
+int tty_set_ldisc(struct tty_struct *tty, int disc)
 {
 	int retval;
 	struct tty_ldisc *old_ldisc, *new_ldisc;
 
-	new_ldisc = tty_ldisc_get(tty, ldisc);
+	new_ldisc = tty_ldisc_get(tty, disc);
 	if (IS_ERR(new_ldisc))
 		return PTR_ERR(new_ldisc);
 
@@ -539,8 +548,13 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 	if (retval)
 		goto err;
 
+	if (!tty->ldisc) {
+		retval = -EIO;
+		goto out;
+	}
+
 	/* Check the no-op case */
-	if (tty->ldisc->ops->num == ldisc)
+	if (tty->ldisc->ops->num == disc)
 		goto out;
 
 	if (test_bit(TTY_HUPPED, &tty->flags)) {
@@ -556,7 +570,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
 	/* Now set up the new line discipline. */
 	tty->ldisc = new_ldisc;
-	tty_set_termios_ldisc(tty, ldisc);
+	tty_set_termios_ldisc(tty, disc);
 
 	retval = tty_ldisc_open(tty, new_ldisc);
 	if (retval < 0) {
@@ -590,6 +604,25 @@ err:
 }
 
 /**
+ *	tty_ldisc_kill	-	teardown ldisc
+ *	@tty: tty being released
+ *
+ *	Perform final close of the ldisc and reset tty->ldisc
+ */
+static void tty_ldisc_kill(struct tty_struct *tty)
+{
+	if (!tty->ldisc)
+		return;
+	/*
+	 * Now kill off the ldisc
+	 */
+	tty_ldisc_close(tty, tty->ldisc);
+	tty_ldisc_put(tty->ldisc);
+	/* Force an oops if we mess this up */
+	tty->ldisc = NULL;
+}
+
+/**
  *	tty_reset_termios	-	reset terminal state
  *	@tty: tty to reset
  *
@@ -609,28 +642,44 @@ static void tty_reset_termios(struct tty_struct *tty)
 /**
  *	tty_ldisc_reinit	-	reinitialise the tty ldisc
  *	@tty: tty to reinit
- *	@ldisc: line discipline to reinitialize
+ *	@disc: line discipline to reinitialize
+ *
+ *	Completely reinitialize the line discipline state, by closing the
+ *	current instance, if there is one, and opening a new instance. If
+ *	an error occurs opening the new non-N_TTY instance, the instance
+ *	is dropped and tty->ldisc reset to NULL. The caller can then retry
+ *	with N_TTY instead.
  *
- *	Switch the tty to a line discipline and leave the ldisc
- *	state closed
+ *	Returns 0 if successful, otherwise error code < 0
  */
 
-static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
+int tty_ldisc_reinit(struct tty_struct *tty, int disc)
 {
-	struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc);
+	struct tty_ldisc *ld;
+	int retval;
 
-	if (IS_ERR(ld))
-		return -1;
+	ld = tty_ldisc_get(tty, disc);
+	if (IS_ERR(ld)) {
+		BUG_ON(disc == N_TTY);
+		return PTR_ERR(ld);
+	}
 
-	tty_ldisc_close(tty, tty->ldisc);
-	tty_ldisc_put(tty->ldisc);
-	/*
-	 *	Switch the line discipline back
-	 */
-	tty->ldisc = ld;
-	tty_set_termios_ldisc(tty, ldisc);
+	if (tty->ldisc) {
+		tty_ldisc_close(tty, tty->ldisc);
+		tty_ldisc_put(tty->ldisc);
+	}
 
-	return 0;
+	/* switch the line discipline */
+	tty->ldisc = ld;
+	tty_set_termios_ldisc(tty, disc);
+	retval = tty_ldisc_open(tty, tty->ldisc);
+	if (retval) {
+		if (!WARN_ON(disc == N_TTY)) {
+			tty_ldisc_put(tty->ldisc);
+			tty->ldisc = NULL;
+		}
+	}
+	return retval;
 }
 
 /**
@@ -648,13 +697,11 @@ static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
  *	tty itself so we must be careful about locking rules.
  */
 
-void tty_ldisc_hangup(struct tty_struct *tty)
+void tty_ldisc_hangup(struct tty_struct *tty, bool reinit)
 {
 	struct tty_ldisc *ld;
-	int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
-	int err = 0;
 
-	tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc);
+	tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc);
 
 	ld = tty_ldisc_ref(tty);
 	if (ld != NULL) {
@@ -680,31 +727,17 @@ void tty_ldisc_hangup(struct tty_struct *tty)
 	 */
 	tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT);
 
-	if (tty->ldisc) {
-
-		/* At this point we have a halted ldisc; we want to close it and
-		   reopen a new ldisc. We could defer the reopen to the next
-		   open but it means auditing a lot of other paths so this is
-		   a FIXME */
-		if (reset == 0) {
+	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
+		tty_reset_termios(tty);
 
-			if (!tty_ldisc_reinit(tty, tty->termios.c_line))
-				err = tty_ldisc_open(tty, tty->ldisc);
-			else
-				err = 1;
-		}
-		/* If the re-open fails or we reset then go to N_TTY. The
-		   N_TTY open cannot fail */
-		if (reset || err) {
-			BUG_ON(tty_ldisc_reinit(tty, N_TTY));
-			WARN_ON(tty_ldisc_open(tty, tty->ldisc));
-		}
+	if (tty->ldisc) {
+		if (reinit) {
+			if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0)
+				tty_ldisc_reinit(tty, N_TTY);
+		} else
+			tty_ldisc_kill(tty);
 	}
 	tty_ldisc_unlock(tty);
-	if (reset)
-		tty_reset_termios(tty);
-
-	tty_ldisc_debug(tty, "%p: re-opened\n", tty->ldisc);
 }
 
 /**
@@ -719,44 +752,26 @@ void tty_ldisc_hangup(struct tty_struct *tty)
 
 int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
 {
-	struct tty_ldisc *ld = tty->ldisc;
-	int retval;
-
-	retval = tty_ldisc_open(tty, ld);
+	int retval = tty_ldisc_open(tty, tty->ldisc);
 	if (retval)
 		return retval;
 
 	if (o_tty) {
 		retval = tty_ldisc_open(o_tty, o_tty->ldisc);
 		if (retval) {
-			tty_ldisc_close(tty, ld);
+			tty_ldisc_close(tty, tty->ldisc);
 			return retval;
 		}
 	}
 	return 0;
 }
 
-static void tty_ldisc_kill(struct tty_struct *tty)
-{
-	/*
-	 * Now kill off the ldisc
-	 */
-	tty_ldisc_close(tty, tty->ldisc);
-	tty_ldisc_put(tty->ldisc);
-	/* Force an oops if we mess this up */
-	tty->ldisc = NULL;
-
-	/* Ensure the next open requests the N_TTY ldisc */
-	tty_set_termios_ldisc(tty, N_TTY);
-}
-
 /**
  *	tty_ldisc_release		-	release line discipline
  *	@tty: tty being shut down (or one end of pty pair)
  *
  *	Called during the final close of a tty or a pty pair in order to shut
- *	down the line discpline layer. On exit, each ldisc assigned is N_TTY and
- *	each ldisc has not been opened.
+ *	down the line discpline layer. On exit, each tty's ldisc is NULL.
  */
 
 void tty_ldisc_release(struct tty_struct *tty)
@@ -797,7 +812,7 @@ void tty_ldisc_init(struct tty_struct *tty)
 }
 
 /**
- *	tty_ldisc_init		-	ldisc cleanup for new tty
+ *	tty_ldisc_deinit	-	ldisc cleanup for new tty
  *	@tty: tty that was allocated recently
  *
  *	The tty structure must not becompletely set up (tty_ldisc_setup) when
@@ -805,12 +820,7 @@ void tty_ldisc_init(struct tty_struct *tty)
  */
 void tty_ldisc_deinit(struct tty_struct *tty)
 {
-	tty_ldisc_put(tty->ldisc);
+	if (tty->ldisc)
+		tty_ldisc_put(tty->ldisc);
 	tty->ldisc = NULL;
 }
-
-void tty_ldisc_begin(void)
-{
-	/* Setup the default TTY line discipline. */
-	(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
-}