The following functions are supported:
- write, read potentiometer value
- potentiometer scale
Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1803.pdf
Signed-off-by: Slawomir Stepien <[email protected]>
---
.../bindings/iio/potentiometer/ds1803.txt | 21 +++
drivers/iio/potentiometer/Kconfig | 10 ++
drivers/iio/potentiometer/Makefile | 1 +
drivers/iio/potentiometer/ds1803.c | 178 +++++++++++++++++++++
4 files changed, 210 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt
create mode 100644 drivers/iio/potentiometer/ds1803.c
diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt b/Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt
new file mode 100644
index 0000000..df77bf5
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt
@@ -0,0 +1,21 @@
+* Maxim Integrated DS1803 digital potentiometer driver
+
+The node for this driver must be a child node of a I2C controller, hence
+all mandatory properties for your controller must be specified. See directory:
+
+ Documentation/devicetree/bindings/i2c
+
+for more details.
+
+Required properties:
+ - compatible: Must be one of the following, depending on the
+ model:
+ "maxim,ds1803-010",
+ "maxim,ds1803-050",
+ "maxim,ds1803-100"
+
+Example:
+ds1803: ds1803@1 {
+ reg = <0x28>;
+ compatible = "maxim,ds1803-010";
+};
diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index 7ea069b..6acb238 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -5,6 +5,16 @@
menu "Digital potentiometers"
+config DS1803
+ tristate "Maxim Integrated DS1803 Digital Potentiometer driver"
+ depends on I2C
+ help
+ Say yes here to build support for the Maxim Integrated DS1803
+ digital potentiomenter chip.
+
+ To compile this driver as a module, choose M here: the
+ module will be called ds1803.
+
config MCP4131
tristate "Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X Digital Potentiometer driver"
depends on SPI
diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
index 91a80f8..6007faa 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -3,6 +3,7 @@
#
# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_DS1803) += ds1803.o
obj-$(CONFIG_MCP4131) += mcp4131.o
obj-$(CONFIG_MCP4531) += mcp4531.o
obj-$(CONFIG_TPL0102) += tpl0102.o
diff --git a/drivers/iio/potentiometer/ds1803.c b/drivers/iio/potentiometer/ds1803.c
new file mode 100644
index 0000000..b5e5b1c
--- /dev/null
+++ b/drivers/iio/potentiometer/ds1803.c
@@ -0,0 +1,178 @@
+/*
+ * Maxim Integrated DS1803 digital potentiometer driver
+ * Copyright (c) 2016 Slawomir Stepien
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1803.pdf
+ *
+ * DEVID #Wipers #Positions Resistor Opts (kOhm) i2c address
+ * ds1803 2 256 10, 50, 100 0101xxx
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/cache.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/of.h>
+
+#define DS1803_NUM_WIPERS 2
+#define DS1803_MAX_POS 255
+#define DS1803_WRITE(n) (0xA8 | ((n) + 1))
+
+enum ds1803_type {
+ DS1803_010,
+ DS1803_050,
+ DS1803_100,
+};
+
+struct ds1803_cfg {
+ int kohms;
+};
+
+static const struct ds1803_cfg ds1803_cfg[] = {
+ [DS1803_010] = { .kohms = 10, },
+ [DS1803_050] = { .kohms = 50, },
+ [DS1803_100] = { .kohms = 100, },
+};
+
+struct ds1803_data {
+ struct i2c_client *client;
+ const struct ds1803_cfg *cfg;
+};
+
+#define DS1803_CHANNEL(ch) { \
+ .type = IIO_RESISTANCE, \
+ .indexed = 1, \
+ .output = 1, \
+ .channel = (ch), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec ds1803_channels[] = {
+ DS1803_CHANNEL(0),
+ DS1803_CHANNEL(1),
+};
+
+static int ds1803_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct ds1803_data *data = iio_priv(indio_dev);
+ int pot = chan->channel;
+ s32 ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ ret = i2c_smbus_read_word_swapped(data->client, 0);
+ if (ret < 0)
+ return ret;
+
+ /* Get bits for given pot */
+ *val = (pot == 0 ? ret >> 8 : ret & 255);
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ *val = 1000 * data->cfg->kohms;
+ *val2 = DS1803_MAX_POS;
+ return IIO_VAL_FRACTIONAL;
+ }
+
+ return -EINVAL;
+}
+
+static int ds1803_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct ds1803_data *data = iio_priv(indio_dev);
+ int pot = chan->channel;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ if (val > DS1803_MAX_POS || val < 0)
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return i2c_smbus_write_byte_data(data->client, DS1803_WRITE(pot), val);
+}
+
+static const struct iio_info ds1803_info = {
+ .read_raw = ds1803_read_raw,
+ .write_raw = ds1803_write_raw,
+ .driver_module = THIS_MODULE,
+};
+
+static int ds1803_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct device *dev = &client->dev;
+ struct ds1803_data *data;
+ struct iio_dev *indio_dev;
+
+ /* Value of two pots is read at the same time */
+ if (!i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_WORD_DATA)) {
+ dev_err(dev, "SMBUS Word Data not supported\n");
+ return -EOPNOTSUPP;
+ }
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ i2c_set_clientdata(client, indio_dev);
+
+ data = iio_priv(indio_dev);
+ data->client = client;
+ data->cfg = &ds1803_cfg[id->driver_data];
+
+ indio_dev->dev.parent = dev;
+ indio_dev->info = &ds1803_info;
+ indio_dev->channels = ds1803_channels;
+ indio_dev->num_channels = DS1803_NUM_WIPERS;
+ indio_dev->name = client->name;
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id ds1803_dt_ids[] = {
+ { .compatible = "maxim,ds1803-010", .data = &ds1803_cfg[DS1803_010] },
+ { .compatible = "maxim,ds1803-050", .data = &ds1803_cfg[DS1803_050] },
+ { .compatible = "maxim,ds1803-100", .data = &ds1803_cfg[DS1803_100] },
+ {}
+};
+MODULE_DEVICE_TABLE(of, ds1803_dt_ids);
+#endif /* CONFIG_OF */
+
+static const struct i2c_device_id ds1803_id[] = {
+ { "ds1803-010", DS1803_010 },
+ { "ds1803-050", DS1803_050 },
+ { "ds1803-100", DS1803_100 },
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, ds1803_id);
+
+static struct i2c_driver ds1803_driver = {
+ .driver = {
+ .name = "ds1803",
+ .of_match_table = of_match_ptr(ds1803_dt_ids),
+ },
+ .probe = ds1803_probe,
+ .id_table = ds1803_id,
+};
+
+module_i2c_driver(ds1803_driver);
+
+MODULE_AUTHOR("Slawomir Stepien <[email protected]>");
+MODULE_DESCRIPTION("DS1803 digital potentiometer");
+MODULE_LICENSE("GPL v2");
--
2.7.4
> The following functions are supported:
> - write, read potentiometer value
> - potentiometer scale
minor comments below, nice driver
> Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1803.pdf
>
> Signed-off-by: Slawomir Stepien <[email protected]>
> ---
> .../bindings/iio/potentiometer/ds1803.txt | 21 +++
> drivers/iio/potentiometer/Kconfig | 10 ++
> drivers/iio/potentiometer/Makefile | 1 +
> drivers/iio/potentiometer/ds1803.c | 178 +++++++++++++++++++++
> 4 files changed, 210 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt
> create mode 100644 drivers/iio/potentiometer/ds1803.c
>
> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt b/Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt
> new file mode 100644
> index 0000000..df77bf5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiometer/ds1803.txt
> @@ -0,0 +1,21 @@
> +* Maxim Integrated DS1803 digital potentiometer driver
> +
> +The node for this driver must be a child node of a I2C controller, hence
> +all mandatory properties for your controller must be specified. See directory:
> +
> + Documentation/devicetree/bindings/i2c
> +
> +for more details.
> +
> +Required properties:
> + - compatible: Must be one of the following, depending on the
> + model:
> + "maxim,ds1803-010",
> + "maxim,ds1803-050",
> + "maxim,ds1803-100"
> +
> +Example:
> +ds1803: ds1803@1 {
> + reg = <0x28>;
> + compatible = "maxim,ds1803-010";
> +};
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 7ea069b..6acb238 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -5,6 +5,16 @@
>
> menu "Digital potentiometers"
>
> +config DS1803
> + tristate "Maxim Integrated DS1803 Digital Potentiometer driver"
> + depends on I2C
> + help
> + Say yes here to build support for the Maxim Integrated DS1803
> + digital potentiomenter chip.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called ds1803.
> +
> config MCP4131
> tristate "Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X Digital Potentiometer driver"
> depends on SPI
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 91a80f8..6007faa 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -3,6 +3,7 @@
> #
>
> # When adding new entries keep the list in alphabetical order
> +obj-$(CONFIG_DS1803) += ds1803.o
> obj-$(CONFIG_MCP4131) += mcp4131.o
> obj-$(CONFIG_MCP4531) += mcp4531.o
> obj-$(CONFIG_TPL0102) += tpl0102.o
> diff --git a/drivers/iio/potentiometer/ds1803.c b/drivers/iio/potentiometer/ds1803.c
> new file mode 100644
> index 0000000..b5e5b1c
> --- /dev/null
> +++ b/drivers/iio/potentiometer/ds1803.c
> @@ -0,0 +1,178 @@
> +/*
> + * Maxim Integrated DS1803 digital potentiometer driver
> + * Copyright (c) 2016 Slawomir Stepien
> + *
> + * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1803.pdf
> + *
> + * DEVID #Wipers #Positions Resistor Opts (kOhm) i2c address
> + * ds1803 2 256 10, 50, 100 0101xxx
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + */
> +
> +#include <linux/cache.h>
for what is cache.h needed?
> +#include <linux/err.h>
> +#include <linux/export.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +
> +#define DS1803_NUM_WIPERS 2
> +#define DS1803_MAX_POS 255
> +#define DS1803_WRITE(n) (0xA8 | ((n) + 1))
> +
> +enum ds1803_type {
> + DS1803_010,
> + DS1803_050,
> + DS1803_100,
> +};
> +
> +struct ds1803_cfg {
> + int kohms;
> +};
> +
> +static const struct ds1803_cfg ds1803_cfg[] = {
> + [DS1803_010] = { .kohms = 10, },
> + [DS1803_050] = { .kohms = 50, },
> + [DS1803_100] = { .kohms = 100, },
> +};
> +
> +struct ds1803_data {
> + struct i2c_client *client;
> + const struct ds1803_cfg *cfg;
> +};
> +
> +#define DS1803_CHANNEL(ch) { \
> + .type = IIO_RESISTANCE, \
> + .indexed = 1, \
> + .output = 1, \
> + .channel = (ch), \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> +}
> +
> +static const struct iio_chan_spec ds1803_channels[] = {
> + DS1803_CHANNEL(0),
> + DS1803_CHANNEL(1),
> +};
> +
> +static int ds1803_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct ds1803_data *data = iio_priv(indio_dev);
> + int pot = chan->channel;
> + s32 ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + ret = i2c_smbus_read_word_swapped(data->client, 0);
maybe a #define to explain the name of register 0
> + if (ret < 0)
> + return ret;
> +
> + /* Get bits for given pot */
> + *val = (pot == 0 ? ret >> 8 : ret & 255);
often 0xff is used to mask a byte
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_SCALE:
> + *val = 1000 * data->cfg->kohms;
> + *val2 = DS1803_MAX_POS;
> + return IIO_VAL_FRACTIONAL;
> + }
> +
> + return -EINVAL;
> +}
> +
> +static int ds1803_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val, int val2, long mask)
> +{
> + struct ds1803_data *data = iio_priv(indio_dev);
> + int pot = chan->channel;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + if (val > DS1803_MAX_POS || val < 0)
check that val2 is 0 or use .write_raw_get_fmt
> + return -EINVAL;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return i2c_smbus_write_byte_data(data->client, DS1803_WRITE(pot), val);
> +}
> +
> +static const struct iio_info ds1803_info = {
> + .read_raw = ds1803_read_raw,
> + .write_raw = ds1803_write_raw,
> + .driver_module = THIS_MODULE,
> +};
> +
> +static int ds1803_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct device *dev = &client->dev;
> + struct ds1803_data *data;
> + struct iio_dev *indio_dev;
> +
> + /* Value of two pots is read at the same time */
> + if (!i2c_check_functionality(client->adapter,
> + I2C_FUNC_SMBUS_WORD_DATA)) {
> + dev_err(dev, "SMBUS Word Data not supported\n");
> + return -EOPNOTSUPP;
> + }
> +
> + indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + i2c_set_clientdata(client, indio_dev);
> +
> + data = iio_priv(indio_dev);
> + data->client = client;
> + data->cfg = &ds1803_cfg[id->driver_data];
> +
> + indio_dev->dev.parent = dev;
> + indio_dev->info = &ds1803_info;
> + indio_dev->channels = ds1803_channels;
> + indio_dev->num_channels = DS1803_NUM_WIPERS;
ARRAY_SIZE(ds1803_channels)
> + indio_dev->name = client->name;
> +
> + return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +#if defined(CONFIG_OF)
> +static const struct of_device_id ds1803_dt_ids[] = {
> + { .compatible = "maxim,ds1803-010", .data = &ds1803_cfg[DS1803_010] },
> + { .compatible = "maxim,ds1803-050", .data = &ds1803_cfg[DS1803_050] },
> + { .compatible = "maxim,ds1803-100", .data = &ds1803_cfg[DS1803_100] },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, ds1803_dt_ids);
> +#endif /* CONFIG_OF */
> +
> +static const struct i2c_device_id ds1803_id[] = {
> + { "ds1803-010", DS1803_010 },
> + { "ds1803-050", DS1803_050 },
> + { "ds1803-100", DS1803_100 },
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, ds1803_id);
> +
> +static struct i2c_driver ds1803_driver = {
> + .driver = {
> + .name = "ds1803",
> + .of_match_table = of_match_ptr(ds1803_dt_ids),
> + },
> + .probe = ds1803_probe,
> + .id_table = ds1803_id,
> +};
> +
> +module_i2c_driver(ds1803_driver);
> +
> +MODULE_AUTHOR("Slawomir Stepien <[email protected]>");
> +MODULE_DESCRIPTION("DS1803 digital potentiometer");
> +MODULE_LICENSE("GPL v2");
>
--
Peter Meerwald-Stadler
+43-664-2444418 (mobile)
On Apr 07, 2016 21:36, Peter Meerwald-Stadler wrote:
>
> > The following functions are supported:
> > - write, read potentiometer value
> > - potentiometer scale
>
> minor comments below, nice driver
Thank you for your comments!
> > +#include <linux/cache.h>
>
> for what is cache.h needed?
It is not needed here. I will delete it in v2.
> > +static int ds1803_read_raw(struct iio_dev *indio_dev,
> > + struct iio_chan_spec const *chan,
> > + int *val, int *val2, long mask)
> > +{
> > + struct ds1803_data *data = iio_priv(indio_dev);
> > + int pot = chan->channel;
> > + s32 ret;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + ret = i2c_smbus_read_word_swapped(data->client, 0);
>
> maybe a #define to explain the name of register 0
Well this zero is not register nor any kind of command that DS1803 needs to send
back pots values.
DS1803 only requires the standard R/W bit to be set as read.
I used _word_ function series to get back a word (16 bits) as this poti returns
16 bits.
How should I named it?
#define NON_COMMAND 0
?
Or should I use different function? (2x i2c_smbus_read_byte?)
The i2c_smbus_read_byte() function also used 0 as command
for its transfers...
> > + if (ret < 0)
> > + return ret;
> > +
> > + /* Get bits for given pot */
> > + *val = (pot == 0 ? ret >> 8 : ret & 255);
>
> often 0xff is used to mask a byte
OK.
> > + return IIO_VAL_INT;
> > +
> > + case IIO_CHAN_INFO_SCALE:
> > + *val = 1000 * data->cfg->kohms;
> > + *val2 = DS1803_MAX_POS;
> > + return IIO_VAL_FRACTIONAL;
> > + }
> > +
> > + return -EINVAL;
> > +}
> > +
> > +static int ds1803_write_raw(struct iio_dev *indio_dev,
> > + struct iio_chan_spec const *chan,
> > + int val, int val2, long mask)
> > +{
> > + struct ds1803_data *data = iio_priv(indio_dev);
> > + int pot = chan->channel;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + if (val > DS1803_MAX_POS || val < 0)
>
> check that val2 is 0 or use .write_raw_get_fmt
At this point I do not know why should I do it, but I will look into that.
> > + indio_dev->dev.parent = dev;
> > + indio_dev->info = &ds1803_info;
> > + indio_dev->channels = ds1803_channels;
> > + indio_dev->num_channels = DS1803_NUM_WIPERS;
>
> ARRAY_SIZE(ds1803_channels)
Good point.
--
Slawomir Stepien
> > maybe a #define to explain the name of register 0
>
> Well this zero is not register nor any kind of command that DS1803 needs to send
> back pots values.
> DS1803 only requires the standard R/W bit to be set as read.
> I used _word_ function series to get back a word (16 bits) as this poti returns
> 16 bits.
>
> How should I named it?
>
> #define NON_COMMAND 0
> ?
maybe i2c_transfer() is more appropriate then
u8 databuf[2];
struct i2c_msg msgs[2] = {
{ .addr = client->addr, .len = sizeof(databuf), .buf = databuf,
.flags = I2C_M_RD } };
ret = i2c_transfer(client->adapter, msgs, 2);
this does not send any data to the chip but only reads two bytes
> Or should I use different function? (2x i2c_smbus_read_byte?)
>
> The i2c_smbus_read_byte() function also used 0 as command
> for its transfers...
> > > +static int ds1803_write_raw(struct iio_dev *indio_dev,
> > > + struct iio_chan_spec const *chan,
> > > + int val, int val2, long mask)
> > > +{
> > > + struct ds1803_data *data = iio_priv(indio_dev);
> > > + int pot = chan->channel;
> > > +
> > > + switch (mask) {
> > > + case IIO_CHAN_INFO_RAW:
> > > + if (val > DS1803_MAX_POS || val < 0)
> >
> > check that val2 is 0 or use .write_raw_get_fmt
>
> At this point I do not know why should I do it, but I will look into that.
write_raw expects a VAL_INT_PLUS_MICROS per default, passed
in val and val2
you can change that with .write_raw_get_fmt (e.g. to expect VAL_INT),
or just make sure that the micros are 0
--
Peter Meerwald-Stadler
+43-664-2444418 (mobile)
On Apr 08, 2016 18:00, Peter Meerwald-Stadler wrote:
>
> > > maybe a #define to explain the name of register 0
> >
> > Well this zero is not register nor any kind of command that DS1803 needs to send
> > back pots values.
> > DS1803 only requires the standard R/W bit to be set as read.
> > I used _word_ function series to get back a word (16 bits) as this poti returns
> > 16 bits.
> >
> > How should I named it?
> >
> > #define NON_COMMAND 0
> > ?
>
> maybe i2c_transfer() is more appropriate then
>
> u8 databuf[2];
> struct i2c_msg msgs[2] = {
> { .addr = client->addr, .len = sizeof(databuf), .buf = databuf,
> .flags = I2C_M_RD } };
> ret = i2c_transfer(client->adapter, msgs, 2);
>
> this does not send any data to the chip but only reads two bytes
Good point. But maybe the better solution would be to use i2c_master_recv?
Anyhow I will check both options ;)
> > Or should I use different function? (2x i2c_smbus_read_byte?)
> >
> > The i2c_smbus_read_byte() function also used 0 as command
> > for its transfers...
>
> > > > +static int ds1803_write_raw(struct iio_dev *indio_dev,
> > > > + struct iio_chan_spec const *chan,
> > > > + int val, int val2, long mask)
> > > > +{
> > > > + struct ds1803_data *data = iio_priv(indio_dev);
> > > > + int pot = chan->channel;
> > > > +
> > > > + switch (mask) {
> > > > + case IIO_CHAN_INFO_RAW:
> > > > + if (val > DS1803_MAX_POS || val < 0)
> > >
> > > check that val2 is 0 or use .write_raw_get_fmt
> >
> > At this point I do not know why should I do it, but I will look into that.
>
> write_raw expects a VAL_INT_PLUS_MICROS per default, passed
> in val and val2
>
> you can change that with .write_raw_get_fmt (e.g. to expect VAL_INT),
> or just make sure that the micros are 0
Thank you for the explanation.
--
Slawomir Stepien