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Message-ID: <20260203093434.2548978-14-o.rempel@pengutronix.de>
Date: Tue, 3 Feb 2026 10:34:33 +0100
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Jonathan Cameron <jic23@...nel.org>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
Andy Shevchenko <andriy.shevchenko@...el.com>,
kernel@...gutronix.de,
linux-kernel@...r.kernel.org,
linux-iio@...r.kernel.org,
devicetree@...r.kernel.org,
Andy Shevchenko <andy@...nel.org>,
David Lechner <dlechner@...libre.com>,
Nuno Sá <nuno.sa@...log.com>,
David Jander <david@...tonic.nl>
Subject: [PATCH v4 13/13] iio: dac: ds4424: add Rfs-based scale and per-variant limits
Parse optional maxim,rfs-ohms values to derive the per-channel output
current scale (mA per step) for the IIO current ABI.
Behavior changes:
- If maxim,rfs-ohms is present, IIO_CHAN_INFO_SCALE becomes available
and reports mA/step derived from Rfs.
- If maxim,rfs-ohms is missing, SCALE is not exposed to keep older DTs
working without requiring updates.
Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>
---
changes v4:
- Split series: moved infrastructure and RAW limit fixes to a preceding patch.
- Replaced dynamic channel allocation (devm_kmemdup_array()) with static
const arrays (ds4424_channels_with_scale) to handle the two states.
- Removed log message when maxim,rfs-ohms is missing.
changes v3:
- Added explicit check for negative return from device_property_count_u32().
- Rename vref_mv to vref_mV
- Use devm_kmemdup_array() instead of devm_kmemdup()
- Use %u for unsigned index in Rfs error logs.
- Consolidated Rfs parse logs to a single line.
changes v2:
- Reorder struct ds4424_chip_info members to optimize padding.
- Use GENMASK() for chip variant masks instead of hex constants.
- Simplify ds4424_setup_channels: use direct devm_kmemdup to avoid stack
usage and memcpy.
- Use local 'dev' pointer and dev_err_probe() in ds4424_parse_rfs for
cleaner error handling.
- Rename the static iio_info struct to ds4424_iio_info to prevent name
collision with the new hardware chip_info structs.
- Use unsigned int for loop counters.
- Rebase on top of regmap and symmetrical raw_access refactoring.
---
drivers/iio/dac/ds4424.c | 81 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 80 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/dac/ds4424.c b/drivers/iio/dac/ds4424.c
index d7ccf031b234..e34a8c3fba87 100644
--- a/drivers/iio/dac/ds4424.c
+++ b/drivers/iio/dac/ds4424.c
@@ -12,6 +12,7 @@
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
+#include <linux/property.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>
@@ -37,27 +38,46 @@
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
}
+#define DS4424_CHANNEL_WITH_SCALE(chan) { \
+ .type = IIO_CURRENT, \
+ .indexed = 1, \
+ .output = 1, \
+ .channel = chan, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ BIT(IIO_CHAN_INFO_SCALE), \
+}
+
struct ds4424_chip_info {
+ int vref_mV;
+ int scale_denom;
u8 result_mask;
u8 num_channels;
};
static const struct ds4424_chip_info ds4402_info = {
+ .vref_mV = 1230,
+ .scale_denom = 4,
.result_mask = DS4404_DAC_MASK,
.num_channels = DS4422_MAX_DAC_CHANNELS,
};
static const struct ds4424_chip_info ds4404_info = {
+ .vref_mV = 1230,
+ .scale_denom = 4,
.result_mask = DS4404_DAC_MASK,
.num_channels = DS4424_MAX_DAC_CHANNELS,
};
static const struct ds4424_chip_info ds4422_info = {
+ .vref_mV = 976,
+ .scale_denom = 16,
.result_mask = DS4424_DAC_MASK,
.num_channels = DS4422_MAX_DAC_CHANNELS,
};
static const struct ds4424_chip_info ds4424_info = {
+ .vref_mV = 976,
+ .scale_denom = 16,
.result_mask = DS4424_DAC_MASK,
.num_channels = DS4424_MAX_DAC_CHANNELS,
};
@@ -66,6 +86,8 @@ struct ds4424_data {
struct regmap *regmap;
struct regulator *vcc_reg;
const struct ds4424_chip_info *chip_info;
+ u32 rfs_ohms[DS4424_MAX_DAC_CHANNELS];
+ bool has_rfs;
};
static const struct iio_chan_spec ds4424_channels[] = {
@@ -75,6 +97,13 @@ static const struct iio_chan_spec ds4424_channels[] = {
DS4424_CHANNEL(3),
};
+static const struct iio_chan_spec ds4424_channels_with_scale[] = {
+ DS4424_CHANNEL_WITH_SCALE(0),
+ DS4424_CHANNEL_WITH_SCALE(1),
+ DS4424_CHANNEL_WITH_SCALE(2),
+ DS4424_CHANNEL_WITH_SCALE(3),
+};
+
static const struct regmap_range ds44x2_ranges[] = {
regmap_reg_range(DS4424_DAC_ADDR(0), DS4424_DAC_ADDR(1)),
};
@@ -167,6 +196,15 @@ static int ds4424_read_raw(struct iio_dev *indio_dev,
*val = -*val;
return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ if (!data->has_rfs)
+ return -EINVAL;
+
+ /* SCALE is mA/step: mV / Ohm = mA. */
+ *val = data->chip_info->vref_mV;
+ *val2 = data->rfs_ohms[chan->channel] *
+ data->chip_info->scale_denom;
+ return IIO_VAL_FRACTIONAL;
default:
return -EINVAL;
@@ -205,6 +243,39 @@ static int ds4424_write_raw(struct iio_dev *indio_dev,
}
}
+static int ds4424_parse_rfs(struct i2c_client *client,
+ struct ds4424_data *data,
+ struct iio_dev *indio_dev)
+{
+ struct device *dev = &client->dev;
+ int count, ret;
+
+ if (!device_property_present(dev, "maxim,rfs-ohms"))
+ return 0;
+
+ count = device_property_count_u32(dev, "maxim,rfs-ohms");
+ if (count < 0)
+ return dev_err_probe(dev, count, "Failed to count maxim,rfs-ohms entries\n");
+ if (count != indio_dev->num_channels)
+ return dev_err_probe(dev, -EINVAL, "maxim,rfs-ohms must have %u entries\n",
+ indio_dev->num_channels);
+
+ ret = device_property_read_u32_array(dev, "maxim,rfs-ohms",
+ data->rfs_ohms,
+ indio_dev->num_channels);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to read maxim,rfs-ohms property\n");
+
+ for (unsigned int i = 0; i < indio_dev->num_channels; i++) {
+ if (!data->rfs_ohms[i])
+ return dev_err_probe(dev, -EINVAL, "maxim,rfs-ohms entry %u is zero\n", i);
+ }
+
+ data->has_rfs = true;
+
+ return 0;
+}
+
static int ds4424_suspend(struct device *dev)
{
struct iio_dev *indio_dev = dev_get_drvdata(dev);
@@ -284,7 +355,6 @@ static int ds4424_probe(struct i2c_client *client)
indio_dev->name = client->name;
indio_dev->num_channels = chip_info->num_channels;
- indio_dev->channels = ds4424_channels;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->info = &ds4424_iio_info;
@@ -292,6 +362,15 @@ static int ds4424_probe(struct i2c_client *client)
if (ret)
goto fail;
+ ret = ds4424_parse_rfs(client, data, indio_dev);
+ if (ret)
+ goto fail;
+
+ if (data->has_rfs)
+ indio_dev->channels = ds4424_channels_with_scale;
+ else
+ indio_dev->channels = ds4424_channels;
+
ret = iio_device_register(indio_dev);
if (ret < 0) {
dev_err(&client->dev,
--
2.47.3
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