[PATCH v4 07/10] iio: adc: ti-ads7924: Respect device tree config

Matti Vaittinen
2025-02-24T18:34:24Z

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The ti-ads7924 driver ignores the device-tree ADC channel specification
and always exposes all 4 channels to users whether they are present in
the device-tree or not. Additionally, the "reg" values in the channel
nodes are ignored, although an error is printed if they are out of range.

Register only the channels described in the device-tree, and use the reg
property as a channel ID.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

---
Revision history:
v3 => v4:
- Adapt to 'drop diff-channel support' changes to ADC-helpers
- select ADC helpers in the Kconfig
v2 => v3: New patch

Please note that this is potentially breaking existing users if they
have wrong values in the device-tree. I believe the device-tree should
ideally be respected, and if it says device X has only one channel, then
we should believe it and not register 4. Well, we don't live in the
ideal world, so even though I believe this is TheRightThingToDo - it may
cause havoc because correct device-tree has not been required from the
day 1. So, please review and test and apply at your own risk :)

As a side note, this might warrant a fixes tag but the adc-helper -stuff
is hardly worth to be backported... (And I've already exceeded my time
budget with this series - hence I'll leave crafting backportable fix to
TI people ;) )

This has only been compile tested! All testing is highly appreciated.
---
drivers/iio/adc/Kconfig | 1 +
drivers/iio/adc/ti-ads7924.c | 78 ++++++++++++++++--------------------
2 files changed, 36 insertions(+), 43 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 0993008a1586..d16082ac2e1f 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1476,6 +1476,7 @@ config TI_ADS7924
tristate "Texas Instruments ADS7924 ADC"
depends on I2C
select REGMAP_I2C
+ select IIO_ADC_HELPER
help
If you say yes here you get support for Texas Instruments ADS7924
4 channels, 12-bit I2C ADC chip.
diff --git a/drivers/iio/adc/ti-ads7924.c b/drivers/iio/adc/ti-ads7924.c
index b1f745f75dbe..e3ac170c73f4 100644
--- a/drivers/iio/adc/ti-ads7924.c
+++ b/drivers/iio/adc/ti-ads7924.c
@@ -22,6 +22,7 @@
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>

+#include <linux/iio/adc-helpers.h>
#include <linux/iio/iio.h>
#include <linux/iio/types.h>

@@ -119,15 +120,12 @@
#define ADS7924_TOTAL_CONVTIME_US (ADS7924_PWRUPTIME_US + ADS7924_ACQTIME_US + \
ADS7924_CONVTIME_US)

-#define ADS7924_V_CHAN(_chan, _addr) { \
- .type = IIO_VOLTAGE, \
- .indexed = 1, \
- .channel = _chan, \
- .address = _addr, \
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
- .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
- .datasheet_name = "AIN"#_chan, \
-}
+static const struct iio_chan_spec ads7924_chan_template = {
+ .type = IIO_VOLTAGE,
+ .indexed = 1,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+};

struct ads7924_data {
struct device *dev;
@@ -182,13 +180,6 @@ static const struct regmap_config ads7924_regmap_config = {
.writeable_reg = ads7924_is_writeable_reg,
};

-static const struct iio_chan_spec ads7924_channels[] = {
- ADS7924_V_CHAN(0, ADS7924_DATA0_U_REG),
- ADS7924_V_CHAN(1, ADS7924_DATA1_U_REG),
- ADS7924_V_CHAN(2, ADS7924_DATA2_U_REG),
- ADS7924_V_CHAN(3, ADS7924_DATA3_U_REG),
-};
-
static int ads7924_get_adc_result(struct ads7924_data *data,
struct iio_chan_spec const *chan, int *val)
{
@@ -251,32 +242,35 @@ static const struct iio_info ads7924_info = {
.read_raw = ads7924_read_raw,
};

-static int ads7924_get_channels_config(struct device *dev)
+static int ads7924_get_channels_config(struct iio_dev *indio_dev,
+ struct device *dev)
{
- struct fwnode_handle *node;
- int num_channels = 0;
+ struct iio_chan_spec *chan_array;
+ int num_channels = 0, i;
+ static const char * const datasheet_names[] = {
+ "AIN0", "AIN1", "AIN2", "AIN3"
+ };

- device_for_each_child_node(dev, node) {
- u32 pval;
- unsigned int channel;
+ num_channels = devm_iio_adc_device_alloc_chaninfo_se(dev,
+ &ads7924_chan_template,
+ ARRAY_SIZE(datasheet_names) - 1,
+ &chan_array);

- if (fwnode_property_read_u32(node, "reg", &pval)) {
- dev_err(dev, "invalid reg on %pfw\n", node);
- continue;
- }
+ if (num_channels < 0)
+ return num_channels;

- channel = pval;
- if (channel >= ADS7924_CHANNELS) {
- dev_err(dev, "invalid channel index %d on %pfw\n",
- channel, node);
- continue;
- }
+ if (!num_channels)
+ return -EINVAL;

- num_channels++;
+ for (i = 0; i < num_channels; i++) {
+ int ch_id = chan_array[i].channel;
+
+ chan_array[i].address = ADS7924_DATA0_U_REG + ch_id;
+ chan_array[i].datasheet_name = datasheet_names[ch_id];
}

- if (!num_channels)
- return -EINVAL;
+ indio_dev->channels = chan_array;
+ indio_dev->num_channels = num_channels;

return 0;
}
@@ -370,18 +364,15 @@ static int ads7924_probe(struct i2c_client *client)

mutex_init(&data->lock);

- indio_dev->name = "ads7924";
- indio_dev->modes = INDIO_DIRECT_MODE;
-
- indio_dev->channels = ads7924_channels;
- indio_dev->num_channels = ARRAY_SIZE(ads7924_channels);
- indio_dev->info = &ads7924_info;
-
- ret = ads7924_get_channels_config(dev);
+ ret = ads7924_get_channels_config(indio_dev, dev);
if (ret < 0)
return dev_err_probe(dev, ret,
"failed to get channels configuration\n");

+ indio_dev->name = "ads7924";
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->info = &ads7924_info;
+
data->regmap = devm_regmap_init_i2c(client, &ads7924_regmap_config);
if (IS_ERR(data->regmap))
return dev_err_probe(dev, PTR_ERR(data->regmap),
@@ -469,3 +460,4 @@ module_i2c_driver(ads7924_driver);
MODULE_AUTHOR("Hugo Villeneuve <hvilleneuve@dimonoff.com>");
MODULE_DESCRIPTION("Texas Instruments ADS7924 ADC I2C driver");
MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_DRIVER");
--
2.48.1

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