iio: adc: ad7780: convert to device-managed functions

With the devm_ad_sd_setup_buffer_and_trigger() helper, it's a bit easier
now to convert the probe of the AD7780 driver to use device-managed
functions.

Only the regulator disable requires a devm_add_action_or_reset() callback.

This change does that, cleaning up the driver a bit.
Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210513120752.90074-9-aardelean@deviqon.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7780.c

@@ -300,6 +300,11 @@ static int ad7780_init_gpios(struct device *dev, struct ad7780_state *st)
 	return 0;
 }
 
+static void ad7780_reg_disable(void *reg)
+{
+	regulator_disable(reg);
+}
+
 static int ad7780_probe(struct spi_device *spi)
 {
 	struct ad7780_state *st;
@@ -318,8 +323,6 @@ static int ad7780_probe(struct spi_device *spi)
 	st->chip_info =
 		&ad7780_chip_info_tbl[spi_get_device_id(spi)->driver_data];
 
-	spi_set_drvdata(spi, indio_dev);
-
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = &st->chip_info->channel;
@@ -340,35 +343,15 @@ static int ad7780_probe(struct spi_device *spi)
 		return ret;
 	}
 
-	ret = ad_sd_setup_buffer_and_trigger(indio_dev);
+	ret = devm_add_action_or_reset(&spi->dev, ad7780_reg_disable, st->reg);
 	if (ret)
-		goto error_disable_reg;
+		return ret;
 
-	ret = iio_device_register(indio_dev);
+	ret = devm_ad_sd_setup_buffer_and_trigger(&spi->dev, indio_dev);
 	if (ret)
-		goto error_cleanup_buffer_and_trigger;
-
-	return 0;
-
-error_cleanup_buffer_and_trigger:
-	ad_sd_cleanup_buffer_and_trigger(indio_dev);
-error_disable_reg:
-	regulator_disable(st->reg);
-
 		return ret;
-}
-
-static int ad7780_remove(struct spi_device *spi)
-{
-	struct iio_dev *indio_dev = spi_get_drvdata(spi);
-	struct ad7780_state *st = iio_priv(indio_dev);
-
-	iio_device_unregister(indio_dev);
-	ad_sd_cleanup_buffer_and_trigger(indio_dev);
 
-	regulator_disable(st->reg);
-
-	return 0;
+	return devm_iio_device_register(&spi->dev, indio_dev);
 }
 
 static const struct spi_device_id ad7780_id[] = {
@@ -385,7 +368,6 @@ static struct spi_driver ad7780_driver = {
 		.name	= "ad7780",
 	},
 	.probe		= ad7780_probe,
-	.remove		= ad7780_remove,
 	.id_table	= ad7780_id,
 };
 module_spi_driver(ad7780_driver);