gpio: tpic2810: Make sure cached buffer has consistent status with h/w status

i2c_smbus_write_byte_data() can fail. To ensure the
cached buffer has consistent status with h/w status, don't
update the cached gpio->buffer if write fails.

Also refactor the code a bit by adding a tpic2810_set_mask_bits()
helper and use it to simplify the code.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpio-tpic2810.c b/drivers/gpio/gpio-tpic2810.c
index 9f020aa..cace79c 100644 (file)
--- a/drivers/gpio/gpio-tpic2810.c
+++ b/drivers/gpio/gpio-tpic2810.c
@@ -57,39 +57,34 @@ static int tpic2810_direction_output(struct gpio_chip *chip,
        return 0;
 }
 
-static void tpic2810_set(struct gpio_chip *chip, unsigned offset, int value)
+static void tpic2810_set_mask_bits(struct gpio_chip *chip, u8 mask, u8 bits)
 {
        struct tpic2810 *gpio = gpiochip_get_data(chip);
+       u8 buffer;
+       int err;
 
        mutex_lock(&gpio->lock);
 
-       if (value)
-               gpio->buffer |= BIT(offset);
-       else
-               gpio->buffer &= ~BIT(offset);
+       buffer = gpio->buffer & ~mask;
+       buffer |= (mask & bits);
 
-       i2c_smbus_write_byte_data(gpio->client, TPIC2810_WS_COMMAND,
-                                 gpio->buffer);
+       err = i2c_smbus_write_byte_data(gpio->client, TPIC2810_WS_COMMAND,
+                                       buffer);
+       if (!err)
+               gpio->buffer = buffer;
 
        mutex_unlock(&gpio->lock);
 }
 
+static void tpic2810_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+       tpic2810_set_mask_bits(chip, BIT(offset), value ? BIT(offset) : 0);
+}
+
 static void tpic2810_set_multiple(struct gpio_chip *chip, unsigned long *mask,
                                  unsigned long *bits)
 {
-       struct tpic2810 *gpio = gpiochip_get_data(chip);
-
-       mutex_lock(&gpio->lock);
-
-       /* clear bits under mask */
-       gpio->buffer &= ~(*mask);
-       /* set bits under mask */
-       gpio->buffer |= ((*mask) & (*bits));
-
-       i2c_smbus_write_byte_data(gpio->client, TPIC2810_WS_COMMAND,
-                                 gpio->buffer);
-
-       mutex_unlock(&gpio->lock);
+       tpic2810_set_mask_bits(chip, *mask, *bits);
 }
 
 static struct gpio_chip template_chip = {