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

David Lechner
2026-03-02T15:06:20Z

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);