[PATCH 05/10] tty: moxa: use guard()s

["Jiri Slaby (SUSE)" <jirislaby@kernel.org>]

Use guards in the moxa code. This improves readability, makes error
handling easier, and marks locked portions of code explicit. All that
while being sure the lock is unlocked.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
 drivers/tty/moxa.c | 169 ++++++++++++++++++++-------------------------
 1 file changed, 73 insertions(+), 96 deletions(-)

diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index 329b30fac8fc..1bb2376af85c 100644
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -487,25 +487,20 @@ static void moxa_wait_finish(void __iomem *ofsAddr)
 
 static void moxafunc(void __iomem *ofsAddr, u16 cmd, u16 arg)
 {
-        unsigned long flags;
-        spin_lock_irqsave(&moxafunc_lock, flags);
+	guard(spinlock_irqsave)(&moxafunc_lock);
 	writew(arg, ofsAddr + FuncArg);
 	writew(cmd, ofsAddr + FuncCode);
 	moxa_wait_finish(ofsAddr);
-	spin_unlock_irqrestore(&moxafunc_lock, flags);
 }
 
 static int moxafuncret(void __iomem *ofsAddr, u16 cmd, u16 arg)
 {
-        unsigned long flags;
-        u16 ret;
-        spin_lock_irqsave(&moxafunc_lock, flags);
+	guard(spinlock_irqsave)(&moxafunc_lock);
 	writew(arg, ofsAddr + FuncArg);
 	writew(cmd, ofsAddr + FuncCode);
 	moxa_wait_finish(ofsAddr);
-	ret = readw(ofsAddr + FuncArg);
-	spin_unlock_irqrestore(&moxafunc_lock, flags);
-	return ret;
+
+	return readw(ofsAddr + FuncArg);
 }
 
 static void moxa_low_water_check(void __iomem *ofsAddr)
@@ -1002,11 +997,11 @@ static int moxa_init_board(struct moxa_board_conf *brd, struct device *dev)
 	if (ret)
 		goto err_free;
 
-	spin_lock_bh(&moxa_lock);
-	brd->ready = 1;
-	if (!timer_pending(&moxaTimer))
-		mod_timer(&moxaTimer, jiffies + HZ / 50);
-	spin_unlock_bh(&moxa_lock);
+	scoped_guard(spinlock_bh, &moxa_lock) {
+		brd->ready = 1;
+		if (!timer_pending(&moxaTimer))
+			mod_timer(&moxaTimer, jiffies + HZ / 50);
+	}
 
 	first_idx = (brd - moxa_boards) * MAX_PORTS_PER_BOARD;
 	for (i = 0; i < brd->numPorts; i++)
@@ -1026,29 +1021,29 @@ static void moxa_board_deinit(struct moxa_board_conf *brd)
 {
 	unsigned int a, opened, first_idx;
 
-	mutex_lock(&moxa_openlock);
-	spin_lock_bh(&moxa_lock);
-	brd->ready = 0;
-	spin_unlock_bh(&moxa_lock);
-
-	/* pci hot-un-plug support */
-	for (a = 0; a < brd->numPorts; a++)
-		if (tty_port_initialized(&brd->ports[a].port))
-			tty_port_tty_hangup(&brd->ports[a].port, false);
-
-	for (a = 0; a < MAX_PORTS_PER_BOARD; a++)
-		tty_port_destroy(&brd->ports[a].port);
+	scoped_guard(mutex, &moxa_openlock) {
+		scoped_guard(spinlock_bh, &moxa_lock)
+			brd->ready = 0;
 
-	while (1) {
-		opened = 0;
+		/* pci hot-un-plug support */
 		for (a = 0; a < brd->numPorts; a++)
 			if (tty_port_initialized(&brd->ports[a].port))
-				opened++;
-		mutex_unlock(&moxa_openlock);
-		if (!opened)
-			break;
-		msleep(50);
-		mutex_lock(&moxa_openlock);
+				tty_port_tty_hangup(&brd->ports[a].port, false);
+
+		for (a = 0; a < MAX_PORTS_PER_BOARD; a++)
+			tty_port_destroy(&brd->ports[a].port);
+
+		while (1) {
+			opened = 0;
+			for (a = 0; a < brd->numPorts; a++)
+				if (tty_port_initialized(&brd->ports[a].port))
+					opened++;
+			if (!opened)
+				break;
+			mutex_unlock(&moxa_openlock);
+			msleep(50);
+			mutex_lock(&moxa_openlock);
+		}
 	}
 
 	first_idx = (brd - moxa_boards) * MAX_PORTS_PER_BOARD;
@@ -1206,12 +1201,9 @@ static void moxa_shutdown(struct tty_port *port)
 static bool moxa_carrier_raised(struct tty_port *port)
 {
 	struct moxa_port *ch = container_of(port, struct moxa_port, port);
-	int dcd;
 
-	spin_lock_irq(&port->lock);
-	dcd = ch->DCDState;
-	spin_unlock_irq(&port->lock);
-	return dcd;
+	guard(spinlock_irq)(&port->lock);
+	return ch->DCDState;
 }
 
 static void moxa_dtr_rts(struct tty_port *port, bool active)
@@ -1225,37 +1217,31 @@ static int moxa_open(struct tty_struct *tty, struct file *filp)
 {
 	struct moxa_board_conf *brd;
 	struct moxa_port *ch;
-	int port;
-
-	port = tty->index;
-	if (mutex_lock_interruptible(&moxa_openlock))
-		return -ERESTARTSYS;
-	brd = &moxa_boards[port / MAX_PORTS_PER_BOARD];
-	if (!brd->ready) {
-		mutex_unlock(&moxa_openlock);
-		return -ENODEV;
-	}
+	int port = tty->index;
 
-	if (port % MAX_PORTS_PER_BOARD >= brd->numPorts) {
-		mutex_unlock(&moxa_openlock);
-		return -ENODEV;
-	}
-
-	ch = &brd->ports[port % MAX_PORTS_PER_BOARD];
-	ch->port.count++;
-	tty->driver_data = ch;
-	tty_port_tty_set(&ch->port, tty);
-	mutex_lock(&ch->port.mutex);
-	if (!tty_port_initialized(&ch->port)) {
-		ch->statusflags = 0;
-		moxa_set_tty_param(tty, &tty->termios);
-		MoxaPortLineCtrl(ch, true, true);
-		MoxaPortEnable(ch);
-		MoxaSetFifo(ch, ch->type == PORT_16550A);
-		tty_port_set_initialized(&ch->port, true);
+	scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &moxa_openlock) {
+		brd = &moxa_boards[port / MAX_PORTS_PER_BOARD];
+		if (!brd->ready)
+			return -ENODEV;
+
+		if (port % MAX_PORTS_PER_BOARD >= brd->numPorts)
+			return -ENODEV;
+
+		ch = &brd->ports[port % MAX_PORTS_PER_BOARD];
+		ch->port.count++;
+		tty->driver_data = ch;
+		tty_port_tty_set(&ch->port, tty);
+
+		guard(mutex)(&ch->port.mutex);
+		if (!tty_port_initialized(&ch->port)) {
+			ch->statusflags = 0;
+			moxa_set_tty_param(tty, &tty->termios);
+			MoxaPortLineCtrl(ch, true, true);
+			MoxaPortEnable(ch);
+			MoxaSetFifo(ch, ch->type == PORT_16550A);
+			tty_port_set_initialized(&ch->port, true);
+		}
 	}
-	mutex_unlock(&ch->port.mutex);
-	mutex_unlock(&moxa_openlock);
 
 	return tty_port_block_til_ready(&ch->port, tty, filp);
 }
@@ -1270,15 +1256,13 @@ static void moxa_close(struct tty_struct *tty, struct file *filp)
 static ssize_t moxa_write(struct tty_struct *tty, const u8 *buf, size_t count)
 {
 	struct moxa_port *ch = tty->driver_data;
-	unsigned long flags;
 	int len;
 
 	if (ch == NULL)
 		return 0;
 
-	spin_lock_irqsave(&moxa_lock, flags);
-	len = MoxaPortWriteData(tty, buf, count);
-	spin_unlock_irqrestore(&moxa_lock, flags);
+	scoped_guard(spinlock_irqsave, &moxa_lock)
+		len = MoxaPortWriteData(tty, buf, count);
 
 	set_bit(LOWWAIT, &ch->statusflags);
 	return len;
@@ -1349,12 +1333,10 @@ static int moxa_tiocmset(struct tty_struct *tty,
 	bool dtr_active, rts_active;
 	struct moxa_port *ch;
 
-	mutex_lock(&moxa_openlock);
+	guard(mutex)(&moxa_openlock);
 	ch = tty->driver_data;
-	if (!ch) {
-		mutex_unlock(&moxa_openlock);
+	if (!ch)
 		return -EINVAL;
-	}
 
 	MoxaPortGetLineOut(ch, &dtr_active, &rts_active);
 	if (set & TIOCM_RTS)
@@ -1366,7 +1348,7 @@ static int moxa_tiocmset(struct tty_struct *tty,
 	if (clear & TIOCM_DTR)
 		dtr_active = false;
 	MoxaPortLineCtrl(ch, dtr_active, rts_active);
-	mutex_unlock(&moxa_openlock);
+
 	return 0;
 }
 
@@ -1415,18 +1397,17 @@ static void moxa_hangup(struct tty_struct *tty)
 
 static void moxa_new_dcdstate(struct moxa_port *p, u8 dcd)
 {
-	unsigned long flags;
 	dcd = !!dcd;
 
-	spin_lock_irqsave(&p->port.lock, flags);
-	if (dcd != p->DCDState) {
-        	p->DCDState = dcd;
-        	spin_unlock_irqrestore(&p->port.lock, flags);
-		if (!dcd)
-			tty_port_tty_hangup(&p->port, true);
+	scoped_guard(spinlock_irqsave, &p->port.lock) {
+		if (dcd == p->DCDState)
+			return;
+
+		p->DCDState = dcd;
 	}
-	else
-		spin_unlock_irqrestore(&p->port.lock, flags);
+
+	if (!dcd)
+		tty_port_tty_hangup(&p->port, true);
 }
 
 static int moxa_poll_port(struct moxa_port *p, unsigned int handle,
@@ -1494,7 +1475,7 @@ static void moxa_poll(struct timer_list *unused)
 	u16 __iomem *ip;
 	unsigned int card, port, served = 0;
 
-	spin_lock(&moxa_lock);
+	guard(spinlock)(&moxa_lock);
 	for (card = 0; card < MAX_BOARDS; card++) {
 		brd = &moxa_boards[card];
 		if (!brd->ready)
@@ -1525,7 +1506,6 @@ static void moxa_poll(struct timer_list *unused)
 
 	if (served)
 		mod_timer(&moxaTimer, jiffies + HZ / 50);
-	spin_unlock(&moxa_lock);
 }
 
 /******************************************************************************/
@@ -1861,13 +1841,11 @@ static int MoxaPortSetTermio(struct moxa_port *port, struct ktermios *termio,
 	baud = MoxaPortSetBaud(port, baud);
 
 	if (termio->c_iflag & (IXON | IXOFF | IXANY)) {
-	        spin_lock_irq(&moxafunc_lock);
+		guard(spinlock_irq)(&moxafunc_lock);
 		writeb(termio->c_cc[VSTART], ofsAddr + FuncArg);
 		writeb(termio->c_cc[VSTOP], ofsAddr + FuncArg1);
 		writeb(FC_SetXonXoff, ofsAddr + FuncCode);
 		moxa_wait_finish(ofsAddr);
-		spin_unlock_irq(&moxafunc_lock);
-
 	}
 	return baud;
 }
@@ -2098,13 +2076,13 @@ static int moxa_get_serial_info(struct tty_struct *tty,
 
 	if (!info)
 		return -ENODEV;
-	mutex_lock(&info->port.mutex);
+	guard(mutex)(&info->port.mutex);
 	ss->type = info->type;
 	ss->line = info->port.tty->index;
 	ss->flags = info->port.flags;
 	ss->baud_base = 921600;
 	ss->close_delay = jiffies_to_msecs(info->port.close_delay) / 10;
-	mutex_unlock(&info->port.mutex);
+
 	return 0;
 }
 
@@ -2120,13 +2098,12 @@ static int moxa_set_serial_info(struct tty_struct *tty,
 
 	close_delay = msecs_to_jiffies(ss->close_delay * 10);
 
-	mutex_lock(&info->port.mutex);
+	guard(mutex)(&info->port.mutex);
 	if (!capable(CAP_SYS_ADMIN)) {
 		if (close_delay != info->port.close_delay ||
 		    ss->type != info->type ||
 		    ((ss->flags & ~ASYNC_USR_MASK) !=
 		     (info->port.flags & ~ASYNC_USR_MASK))) {
-			mutex_unlock(&info->port.mutex);
 			return -EPERM;
 		}
 	} else {
@@ -2136,7 +2113,7 @@ static int moxa_set_serial_info(struct tty_struct *tty,
 
 		info->type = ss->type;
 	}
-	mutex_unlock(&info->port.mutex);
+
 	return 0;
 }
 
-- 
2.51.1