Re: [PATCH v2] iio: adc: ad799x: convert to fully managed resources

[David Lechner <dlechner@baylibre.com>]

On 3/1/26 11:25 PM, Archit Anant wrote:
> Refactor the driver to use device-managed allocations and actions,
> allowing for the complete removal of the ad799x_remove() function
> and simplifying the error paths in probe().
> 
> Key changes:
> - Replace the dynamic rx_buf allocation with a fixed-size, DMA-safe
>   buffer using IIO_DECLARE_DMA_BUFFER_WITH_TS() in the state struct.
>   This avoids memory leaks during scan mode updates and removes the
>   need for manual kfree().

I agree with Andy tht this first change should be split out to a
separate patch.

> - Cache the VCC and VREF voltages in the state structure during probe()
>   to avoid querying the regulator API during fast-path read_raw() calls.
> - Use devm_add_action_or_reset() to register regulator_disable()
>   callbacks for both VCC and VREF regulators.

And regulator stuff as another patch.

> - Convert iio_triggered_buffer_setup() and iio_device_register() to
>   their devm_ variants, ensuring safe, reverse-order unwinding.
> 
> Signed-off-by: Archit Anant <architanant5@gmail.com>
> ---
> Changes in v2:
> - Refactored entire resource management to eliminate remove() function
>   based on feedback from David Lechner and Jonathan Cameron.
> - Cached voltages to prevent mixing manual regulator disables with
>   devm-managed device unregistration.
> 
>  drivers/iio/adc/ad799x.c | 83 +++++++++++++++++++---------------------
>  1 file changed, 40 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
> index 108bb22162ef..4a3db6f0a8d8 100644
> --- a/drivers/iio/adc/ad799x.c
> +++ b/drivers/iio/adc/ad799x.c
> @@ -39,6 +39,7 @@
>  #include <linux/iio/triggered_buffer.h>
>  
>  #define AD799X_CHANNEL_SHIFT			4
> +#define AD799X_MAX_CHANNELS			8
>  
>  /*
>   * AD7991, AD7995 and AD7999 defines
> @@ -133,8 +134,12 @@ struct ad799x_state {
>  	unsigned int			id;
>  	u16				config;
>  
> -	u8				*rx_buf;
>  	unsigned int			transfer_size;
> +
> +	int				vcc_uv;
> +	int				vref_uv;
> +
> +	IIO_DECLARE_DMA_BUFFER_WITH_TS(__be16, rx_buf, AD799X_MAX_CHANNELS);

See v1 discussion. IIO_DECLARE_DMA_BUFFER_WITH_TS() is not needed
after all since this is I2C. IIO_DECLARE_BUFFER_WITH_TS() can be
used instead.

>  };
>  
>  static int ad799x_write_config(struct ad799x_state *st, u16 val)
> @@ -217,11 +222,11 @@ static irqreturn_t ad799x_trigger_handler(int irq, void *p)
>  	}
>  
>  	b_sent = i2c_smbus_read_i2c_block_data(st->client,
> -			cmd, st->transfer_size, st->rx_buf);
> +			cmd, st->transfer_size, (u8 *)st->rx_buf);
>  	if (b_sent < 0)
>  		goto out;
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, st->rx_buf,
> +	iio_push_to_buffers_with_timestamp(indio_dev, &st->rx_buf,
>  			iio_get_time_ns(indio_dev));
>  out:
>  	iio_trigger_notify_done(indio_dev->trig);
> @@ -234,11 +239,6 @@ static int ad799x_update_scan_mode(struct iio_dev *indio_dev,
>  {
>  	struct ad799x_state *st = iio_priv(indio_dev);
>  
> -	kfree(st->rx_buf);
> -	st->rx_buf = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
> -	if (!st->rx_buf)
> -		return -ENOMEM;
> -
>  	st->transfer_size = bitmap_weight(scan_mask,
>  					  iio_get_masklength(indio_dev)) * 2;
>  
> @@ -307,9 +307,9 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_SCALE:
>  		if (st->vref)
> -			ret = regulator_get_voltage(st->vref);
> +			ret = st->vref_uv;
>  		else
> -			ret = regulator_get_voltage(st->reg);
> +			ret = st->vcc_uv;
>  
>  		if (ret < 0)
>  			return ret;

It should not be possible for ret < 0 now.

And we should be able to avoid assigning to ret and rather
assign directly to *val now.

> @@ -781,6 +781,13 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
>  	},
>  };
>  
> +static void ad799x_reg_disable(void *data)
> +{
> +	struct regulator *reg = data;
> +
> +	regulator_disable(reg);
> +}
> +
>  static int ad799x_probe(struct i2c_client *client)
>  {
>  	const struct i2c_device_id *id = i2c_client_get_device_id(client);
> @@ -813,6 +820,14 @@ static int ad799x_probe(struct i2c_client *client)
>  	ret = regulator_enable(st->reg);
>  	if (ret)
>  		return ret;
> +	ret = devm_add_action_or_reset(&client->dev, ad799x_reg_disable, st->reg);
> +	if (ret)
> +		return ret;
> +
> +	ret = regulator_get_voltage(st->reg);
> +	if (ret < 0)
> +		return ret;
> +	st->vcc_uv = ret;
>  
>  	/* check if an external reference is supplied */
>  	if (chip_info->has_vref) {
> @@ -820,7 +835,7 @@ static int ad799x_probe(struct i2c_client *client)
>  		ret = PTR_ERR_OR_ZERO(st->vref);
>  		if (ret) {
>  			if (ret != -ENODEV)
> -				goto error_disable_reg;
> +				return ret;
>  			st->vref = NULL;
>  			dev_info(&client->dev, "Using VCC reference voltage\n");
>  		}
> @@ -830,7 +845,14 @@ 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(&client->dev, ad799x_reg_disable, st->vref);
> +			if (ret)
> +				return ret;
> +			ret = regulator_get_voltage(st->vref);
> +			if (ret < 0)
> +				return ret;
> +			st->vref_uv = ret;
>  		}
>  	}
>  
> @@ -845,12 +867,12 @@ 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(&client->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(&client->dev,
> @@ -862,40 +884,16 @@ 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_iio_device_register(&client->dev, indio_dev);

We can just return directly here now.

>  	if (ret)
> -		goto error_cleanup_ring;
> +		return ret;
>  
>  	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);
> -	kfree(st->rx_buf);
>  }
>  
>  static int ad799x_suspend(struct device *dev)
> @@ -965,7 +963,6 @@ 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);