[PATCH v5 4/4] iio: adc: ad799x: use devm_iio_device_register and drop remove()

[Archit Anant <architanant5@gmail.com>]

Convert the driver to use the device-managed versions of
iio_device_register(), iio_triggered_buffer_setup(), and mutex_init().

Use devm_add_action_or_reset() to ensure that the VCC and VREF
regulators are disabled safely and in the correct order during
driver teardown or probe failure.

Because all resources (buffer, regulators, IRQs, IIO device, mutex)
are now fully managed by the devm core, the unwinding order is
guaranteed to be correct (reverse order of allocation). We can now
safely remove all manual error handling goto labels in ad799x_probe()
and delete the ad799x_remove() function entirely.

This eliminates boilerplate code and prevents potential resource leaks.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Suggested-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Archit Anant <architanant5@gmail.com>
---
 drivers/iio/adc/ad799x.c | 62 ++++++++++++++++------------------------
 1 file changed, 25 insertions(+), 37 deletions(-)

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index ae2ad4bd37cc..3d745612bb80 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -774,6 +774,11 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 };
 
+static void ad799x_reg_disable(void *reg)
+{
+	regulator_disable(reg);
+}
+
 static int ad799x_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
@@ -808,13 +813,17 @@ static int ad799x_probe(struct i2c_client *client)
 	if (ret)
 		return ret;
 
+	ret = devm_add_action_or_reset(dev, ad799x_reg_disable, st->reg);
+	if (ret)
+		return ret;
+
 	/* check if an external reference is supplied */
 	if (chip_info->has_vref) {
 		st->vref = devm_regulator_get_optional(dev, "vref");
 		ret = PTR_ERR_OR_ZERO(st->vref);
 		if (ret) {
 			if (ret != -ENODEV)
-				goto error_disable_reg;
+				return ret;
 			st->vref = NULL;
 			dev_info(dev, "Using VCC reference voltage\n");
 		}
@@ -824,10 +833,15 @@ static int ad799x_probe(struct i2c_client *client)
 			extra_config |= AD7991_REF_SEL;
 			ret = regulator_enable(st->vref);
 			if (ret)
-				goto error_disable_reg;
+				return ret;
+
+			ret = devm_add_action_or_reset(dev, ad799x_reg_disable, st->vref);
+			if (ret)
+				return ret;
+
 			ret = regulator_get_voltage(st->vref);
 			if (ret < 0)
-				goto error_disable_vref;
+				return ret;
 			st->vref_uV = ret;
 		}
 	}
@@ -835,7 +849,7 @@ static int ad799x_probe(struct i2c_client *client)
 	if (!st->vref) {
 		ret = regulator_get_voltage(st->reg);
 		if (ret < 0)
-			goto error_disable_reg;
+			return ret;
 		st->vref_uV = ret;
 	}
 
@@ -850,12 +864,12 @@ static int ad799x_probe(struct i2c_client *client)
 
 	ret = ad799x_update_config(st, st->chip_config->default_config | extra_config);
 	if (ret)
-		goto error_disable_vref;
+		return ret;
 
-	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
 		&ad799x_trigger_handler, NULL);
 	if (ret)
-		goto error_disable_vref;
+		return ret;
 
 	if (client->irq > 0) {
 		ret = devm_request_threaded_irq(dev,
@@ -867,39 +881,14 @@ static int ad799x_probe(struct i2c_client *client)
 						client->name,
 						indio_dev);
 		if (ret)
-			goto error_cleanup_ring;
+			return ret;
 	}
 
-	mutex_init(&st->lock);
-
-	ret = iio_device_register(indio_dev);
+	ret = devm_mutex_init(dev, &st->lock);
 	if (ret)
-		goto error_cleanup_ring;
-
-	return 0;
-
-error_cleanup_ring:
-	iio_triggered_buffer_cleanup(indio_dev);
-error_disable_vref:
-	if (st->vref)
-		regulator_disable(st->vref);
-error_disable_reg:
-	regulator_disable(st->reg);
-
-	return ret;
-}
-
-static void ad799x_remove(struct i2c_client *client)
-{
-	struct iio_dev *indio_dev = i2c_get_clientdata(client);
-	struct ad799x_state *st = iio_priv(indio_dev);
-
-	iio_device_unregister(indio_dev);
+		return ret;
 
-	iio_triggered_buffer_cleanup(indio_dev);
-	if (st->vref)
-		regulator_disable(st->vref);
-	regulator_disable(st->reg);
+	return devm_iio_device_register(dev, indio_dev);
 }
 
 static int ad799x_suspend(struct device *dev)
@@ -969,7 +958,6 @@ static struct i2c_driver ad799x_driver = {
 		.pm = pm_sleep_ptr(&ad799x_pm_ops),
 	},
 	.probe = ad799x_probe,
-	.remove = ad799x_remove,
 	.id_table = ad799x_id,
 };
 module_i2c_driver(ad799x_driver);
-- 
2.39.5