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: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 32 insertions, 6 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 9e0c4fbfc51a..fced1909cbba 100644
--- a/drivers/gpio/Kconfig
+++ b/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
diff --git a/drivers/gpio/pcf857x.c b/drivers/gpio/pcf857x.c
index aa6cc8b2a2bc..d25d356c4f20 100644
--- a/drivers/gpio/pcf857x.c
+++ b/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;