gpio: pcf857x: add lock and handle more chips

Two small updates to the pcf857x driver: (a) the max732[89] chips are
also second sources for the pcf8574/a, and (b) add a mutex to prevent
trashing the cached state.  Adding the lock is effectively a bugfix,
although it seems unlikely that anyone would have run into the issue it
protects against.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/Kconfig

@@ -45,7 +45,7 @@ config GPIO_PCA953X
 	  will be called pca953x.
 
 config GPIO_PCF857X
-	tristate "PCF857x, PCA857x, and PCA967x I2C GPIO expanders"
+	tristate "PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders"
 	depends on I2C
 	help
 	  Say yes here to provide access to most "quasi-bidirectional" I2C
@@ -54,7 +54,8 @@ config GPIO_PCF857X
 	  some of them.  Compatible models include:
 
 	  8 bits:   pcf8574, pcf8574a, pca8574, pca8574a,
-	            pca9670, pca9672, pca9674, pca9674a
+	            pca9670, pca9672, pca9674, pca9674a,
+	  	    max7328, max7329
 
 	  16 bits:  pcf8575, pcf8575c, pca8575,
 	            pca9671, pca9673, pca9675

drivers/gpio/pcf857x.c

@@ -37,6 +37,8 @@ static const struct i2c_device_id pcf857x_id[] = {
 	{ "pca9671", 16 },
 	{ "pca9673", 16 },
 	{ "pca9675", 16 },
+	{ "max7328", 8 },
+	{ "max7329", 8 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, pcf857x_id);
@@ -56,6 +58,7 @@ MODULE_DEVICE_TABLE(i2c, pcf857x_id);
 struct pcf857x {
 	struct gpio_chip	chip;
 	struct i2c_client	*client;
+	struct mutex		lock;		/* protect 'out' */
 	unsigned		out;		/* software latch */
 };
 
@@ -66,9 +69,14 @@ struct pcf857x {
 static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
 {
 	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
+	int		status;
 
+	mutex_lock(&gpio->lock);
 	gpio->out |= (1 << offset);
-	return i2c_smbus_write_byte(gpio->client, gpio->out);
+	status = i2c_smbus_write_byte(gpio->client, gpio->out);
+	mutex_unlock(&gpio->lock);
+
+	return status;
 }
 
 static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
@@ -84,12 +92,17 @@ static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
 {
 	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
 	unsigned	bit = 1 << offset;
+	int		status;
 
+	mutex_lock(&gpio->lock);
 	if (value)
 		gpio->out |= bit;
 	else
 		gpio->out &= ~bit;
-	return i2c_smbus_write_byte(gpio->client, gpio->out);
+	status = i2c_smbus_write_byte(gpio->client, gpio->out);
+	mutex_unlock(&gpio->lock);
+
+	return status;
 }
 
 static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
@@ -124,9 +137,14 @@ static int i2c_read_le16(struct i2c_client *client)
 static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
 {
 	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
+	int		status;
 
+	mutex_lock(&gpio->lock);
 	gpio->out |= (1 << offset);
-	return i2c_write_le16(gpio->client, gpio->out);
+	status = i2c_write_le16(gpio->client, gpio->out);
+	mutex_unlock(&gpio->lock);
+
+	return status;
 }
 
 static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
@@ -142,12 +160,17 @@ static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
 {
 	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
 	unsigned	bit = 1 << offset;
+	int		status;
 
+	mutex_lock(&gpio->lock);
 	if (value)
 		gpio->out |= bit;
 	else
 		gpio->out &= ~bit;
-	return i2c_write_le16(gpio->client, gpio->out);
+	status = i2c_write_le16(gpio->client, gpio->out);
+	mutex_unlock(&gpio->lock);
+
+	return status;
 }
 
 static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
@@ -173,6 +196,8 @@ static int pcf857x_probe(struct i2c_client *client,
 	if (!gpio)
 		return -ENOMEM;
 
+	mutex_init(&gpio->lock);
+
 	gpio->chip.base = pdata->gpio_base;
 	gpio->chip.can_sleep = 1;
 	gpio->chip.owner = THIS_MODULE;