staging:iio:ad7780: Make powerdown GPIO optional

Some designs hardwire the PDRST pin to always on. In this case there is no GPIO
to control the mode of the device, so make the GPIO optional. Since now all of
the the platform data fields are optional now, make the platform data as a whole
optional as well.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/ad7780.c

@@ -73,7 +73,8 @@ static int ad7780_set_mode(struct ad_sigma_delta *sigma_delta,
 		break;
 	}
 
-	gpio_set_value(st->powerdown_gpio, val);
+	if (gpio_is_valid(st->powerdown_gpio))
+		gpio_set_value(st->powerdown_gpio, val);
 
 	return 0;
 }
@@ -148,11 +149,6 @@ static int __devinit ad7780_probe(struct spi_device *spi)
 	struct iio_dev *indio_dev;
 	int ret, voltage_uv = 0;
 
-	if (!pdata) {
-		dev_dbg(&spi->dev, "no platform data?\n");
-		return -ENODEV;
-	}
-
 	indio_dev = iio_device_alloc(sizeof(*st));
 	if (indio_dev == NULL)
 		return -ENOMEM;
@@ -174,8 +170,6 @@ static int __devinit ad7780_probe(struct spi_device *spi)
 	st->chip_info =
 		&ad7780_chip_info_tbl[spi_get_device_id(spi)->driver_data];
 
-	st->powerdown_gpio = pdata->gpio_pdrst;
-
 	if (pdata && pdata->vref_mv)
 		st->int_vref_mv = pdata->vref_mv;
 	else if (voltage_uv)
@@ -192,11 +186,17 @@ static int __devinit ad7780_probe(struct spi_device *spi)
 	indio_dev->num_channels = 1;
 	indio_dev->info = &ad7780_info;
 
-	ret = gpio_request_one(pdata->gpio_pdrst, GPIOF_OUT_INIT_LOW,
+	if (pdata && gpio_is_valid(pdata->gpio_pdrst)) {
+
+		ret = gpio_request_one(pdata->gpio_pdrst, GPIOF_OUT_INIT_LOW,
 			       "AD7780 /PDRST");
-	if (ret) {
-		dev_err(&spi->dev, "failed to request GPIO PDRST\n");
-		goto error_disable_reg;
+		if (ret) {
+			dev_err(&spi->dev, "failed to request GPIO PDRST\n");
+			goto error_disable_reg;
+		}
+		st->powerdown_gpio = pdata->gpio_pdrst;
+	} else {
+		st->powerdown_gpio = -1;
 	}
 
 	ret = ad_sd_setup_buffer_and_trigger(indio_dev);
@@ -212,7 +212,8 @@ static int __devinit ad7780_probe(struct spi_device *spi)
 error_cleanup_buffer_and_trigger:
 	ad_sd_cleanup_buffer_and_trigger(indio_dev);
 error_free_gpio:
-	gpio_free(pdata->gpio_pdrst);
+	if (pdata && gpio_is_valid(pdata->gpio_pdrst))
+		gpio_free(pdata->gpio_pdrst);
 error_disable_reg:
 	if (!IS_ERR(st->reg))
 		regulator_disable(st->reg);
@@ -233,7 +234,9 @@ static int __devexit ad7780_remove(struct spi_device *spi)
 	iio_device_unregister(indio_dev);
 	ad_sd_cleanup_buffer_and_trigger(indio_dev);
 
-	gpio_free(st->powerdown_gpio);
+	if (gpio_is_valid(st->powerdown_gpio))
+		gpio_free(st->powerdown_gpio);
+
 	if (!IS_ERR(st->reg)) {
 		regulator_disable(st->reg);
 		regulator_put(st->reg);