gpio: pca953x: Add set_multiple to allow multiple bits to be set in one write.

Tested with TCA6408 / TCA6416 devices.
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pca953x.c

@@ -350,6 +350,43 @@ static void pca953x_gpio_set_value(struct gpio_chip *gc, unsigned off, int val)
 	mutex_unlock(&chip->i2c_lock);
 }
 
+
+static void pca953x_gpio_set_multiple(struct gpio_chip *gc,
+		unsigned long *mask, unsigned long *bits)
+{
+	struct pca953x_chip *chip = to_pca(gc);
+	u8 reg_val[MAX_BANK];
+	int ret, offset = 0;
+	int bank_shift = fls((chip->gpio_chip.ngpio - 1) / BANK_SZ);
+	int bank;
+
+	switch (chip->chip_type) {
+	case PCA953X_TYPE:
+		offset = PCA953X_OUTPUT;
+		break;
+	case PCA957X_TYPE:
+		offset = PCA957X_OUT;
+		break;
+	}
+
+	memcpy(reg_val, chip->reg_output, NBANK(chip));
+	mutex_lock(&chip->i2c_lock);
+	for(bank=0; bank<NBANK(chip); bank++) {
+		unsigned bankmask = mask[bank/4] >> ((bank % 4) * 8);
+		if(bankmask) {
+			unsigned bankval  = bits[bank/4] >> ((bank % 4) * 8);
+			reg_val[bank] = (reg_val[bank] & ~bankmask) | bankval;
+		}
+	}
+	ret = i2c_smbus_write_i2c_block_data(chip->client, offset << bank_shift, NBANK(chip), reg_val);
+	if (ret)
+		goto exit;
+
+	memcpy(chip->reg_output, reg_val, NBANK(chip));
+exit:
+	mutex_unlock(&chip->i2c_lock);
+}
+
 static void pca953x_setup_gpio(struct pca953x_chip *chip, int gpios)
 {
 	struct gpio_chip *gc;
@@ -360,6 +397,7 @@ static void pca953x_setup_gpio(struct pca953x_chip *chip, int gpios)
 	gc->direction_output = pca953x_gpio_direction_output;
 	gc->get = pca953x_gpio_get_value;
 	gc->set = pca953x_gpio_set_value;
+	gc->set_multiple = pca953x_gpio_set_multiple;
 	gc->can_sleep = true;
 
 	gc->base = chip->gpio_start;