[PATCH v7 5/5] iio: adc: ad799x: convert to fully managed resources and drop remove()

[Archit Anant <architanant5@gmail.com>]

Convert the driver's remaining manual resource management to use the
devm_ infrastructure, allowing for the complete removal of the
ad799x_remove() function and the simplification of the probe error paths.

Specifically:
- Initialize the mutex using devm_mutex_init() and move it to the top
  of probe() (before IRQ registration) to prevent a race condition where
  an interrupt could attempt to take an uninitialized lock.
- 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.
- Refactor the optional VREF error handling path for better readability.
- Convert iio_triggered_buffer_setup() and iio_device_register() to
  their devm_ variants.

Because all resources are now managed by the devm core, the unwinding
order is guaranteed to follow the reverse order of allocation. All manual
error handling goto labels in ad799x_probe() have been removed.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Suggested-by: David Lechner <dlechner@baylibre.com>
Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Archit Anant <architanant5@gmail.com>
---
 drivers/iio/adc/ad799x.c | 69 ++++++++++++++++------------------------
 1 file changed, 28 insertions(+), 41 deletions(-)

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index e37bb64edd2b..9170109d64ef 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -775,6 +775,11 @@ 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;
@@ -793,6 +798,9 @@ static int ad799x_probe(struct i2c_client *client)
 	st = iio_priv(indio_dev);
 	/* this is only used for device removal purposes */
 	i2c_set_clientdata(client, indio_dev);
+	ret = devm_mutex_init(dev, &st->lock);
+	if (ret)
+		return ret;
 
 	st->id = id->driver_data;
 	if (client->irq > 0 && chip_info->irq_config.info)
@@ -809,15 +817,19 @@ 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;
+		if (ret == -ENODEV) {
 			st->vref = NULL;
 			dev_info(dev, "Using VCC reference voltage\n");
+		} else if (ret) {
+			return ret;
 		}
 
 		if (st->vref) {
@@ -825,10 +837,15 @@ 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;
 		}
 	}
@@ -836,7 +853,7 @@ 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;
 	}
 
@@ -851,12 +868,12 @@ 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,
@@ -868,39 +885,10 @@ 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);
-	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);
-
-	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)
@@ -970,7 +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