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

Archit Anant
2026-03-02T05:26:17Z

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().
- 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.
- 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);
};

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;
@@ -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);
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);
--
2.39.5