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SubjectRe: [PATCH] iio: dac: DS4424: add Maxim DS4422/DS4424 DAC driver support
On Fri, 23 Jun 2017 16:04:04 -0700
Ismail Kose <Ismail.Kose@maximintegrated.com> wrote:

> From: "Ismail H. Kose" <ihkose@gmail.com>
>
> Add iio driver for DS4422/DS4424 chips that support two/four channel 7-bit
> Sink/Source Current DAC.
>
> The driver supports device tree and platfrom files for the configurations.
>
> Datasheet publicly available at:
> https://datasheets.maximintegrated.com/en/ds/DS4422-DS4424.pdf
>
> Signed-off-by: Ismail Kose <Ismail.Kose@maximintegrated.com>
Various bits and pieces inline. In places I think you have tried
to make the driver too generic. Rule of thumb is that we'll only
add complexity when necessary. In particular the devicetree
binding seems to be designed to support a range fo devices without
adding explicit kernel support.

Jonathan
> ---
> .../devicetree/bindings/iio/dac/ds4424.txt | 41 ++
> drivers/iio/dac/Kconfig | 9 +
> drivers/iio/dac/Makefile | 1 +
> drivers/iio/dac/ds4424.c | 733 +++++++++++++++++++++
> include/linux/iio/dac/ds4424.h | 29 +
> 5 files changed, 813 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/iio/dac/ds4424.txt
> create mode 100644 drivers/iio/dac/ds4424.c
> create mode 100644 include/linux/iio/dac/ds4424.h
>
> diff --git a/Documentation/devicetree/bindings/iio/dac/ds4424.txt b/Documentation/devicetree/bindings/iio/dac/ds4424.txt
> new file mode 100644
> index 000000000000..03c1b575a6db
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/ds4424.txt
> @@ -0,0 +1,41 @@
> +Maxim Integrated DS4422/DS4424 DAC device driver
> +
> +Required properties:
This is considerably more complex than I would expect after a quick look at
the datasheet.
> + - compatible: Must be "maxim,ds4422" or "maxim,ds4424"
> + - reg: Should contain the DAC I2C address
> + - min_rfs, max_rfs: In order to get the correct processed data values,
> + these resistor values should be changed to the correct values
> + that match the user's system resistor values for RFS0 to RFS1.
> + Resistance values for rfs_resistor are listed in 100 Ohm units;
> + ie, 800 is 80K. Acceptable RFS values are 40K to 160K.
I'm not totally sure why we have these in the device tree... They are (I think)
characteristics that are fixed for a given device type. Certainly seem to be straight
off the data sheet as the recommended range.

> + - ifs_scale: 61000*100 = 6100000 = 100,000,000 * .976/16
Now this is interesting. I'd have thought that given this can be derived
from rfs_restistor and the known v_rfs (off data sheet) - your .976 it wouldn't
make sense to have it in the device tree.

> + - max_picoamp: Should contain DAC maximum pico amper value.
Another element straight off the datasheet. Why would it change for
a given instance? If not shouldn't be in the device tree mapping.
> + - rfs_resistor: Should contain reference resistor
This one is fair enough, but should have a unit in it's name.
Probably rfs_resistor_ohms Should make it clear in this description that
there is an element for each channnel. Don't play the games to have
units that are multiples of 100 ohms. Just validate whatever is
provided in the driver.
> + - iio map: Should contain IIO Map info
This doesn't match the naming in the binding example.
> +
> +Optional properties:
> + - vcc-supply: Power supply us optional. If not defined, driver will ignore it.
> +
> +Example:
> + ds4224@10 {
> + compatible = "maxim,ds4424";
> + reg = <0x10>; /* When A0, A1 pins are ground */
> + vcc-supply = "dac_vcc_3v3";
> + max-picoamp = <200000000>; /* 200uA */
> + ifs-scale = <61000>;
> + /* In order to get the correct processed data values,
> + these resistor values should be changed to the correct values that match the
> + user's system resistor values for RFS0 to RFS1.
> + Resistance values for rfs_resistor are listed in 100 Ohm units;
> + ie, 800 is 80K. Acceptable RFS values are 40K to 160K.
> + */
> + min-rfs = <400>;
> + max-rfs = <1600>;
> + rfs-resistors = <400 800 1000 1600>;
> + dac-iio-map =
> + /* consumer_dev_name, consumer_channel, adc_channel_label */
> + "ds4424_dac-consumer-dev_name-1", "ds4424_dac1", "OUT1",
> + "ds4424_dac-consumer-dev_name-2", "ds4424_dac2", "OUT2",
> + "ds4424_dac-consumer-dev_name-3", "ds4424_dac3", "OUT3",
> + "ds4424_dac-consumer-dev_name-4", "ds4424_dac4", "OUT4";
Whilst they may not be ideal, there are standard ways of handling an iio-map in
devicetree. See Documentation/bindings/iio/iio-bindings.txt

> + };
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index df5abc46cd3f..6f569c0ac88a 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -309,4 +309,13 @@ config VF610_DAC
> This driver can also be built as a module. If so, the module will
> be called vf610_dac.
>
> +config DAC_DS4424
> + tristate "Maxim Integrated DS4422/DS4424 DAC driver"
> + depends on I2C
> + help
> + If you say yes here you get support for Maxim chip DS4422, DS4424.
> +
> + This driver can also be built as a module. If so, the module
> + will be called DAC_DS4424.
> +
> endmenu
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 603587cc2f07..fa77510a5538 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -33,3 +33,4 @@ obj-$(CONFIG_MCP4922) += mcp4922.o
> obj-$(CONFIG_STM32_DAC_CORE) += stm32-dac-core.o
> obj-$(CONFIG_STM32_DAC) += stm32-dac.o
> obj-$(CONFIG_VF610_DAC) += vf610_dac.o
> +obj-$(CONFIG_DAC_DS4424) += ds4424.o
It's a directory of DACs so unless there is a DS4424 that does other stuff,
just call the symbol CONFIG_DS4424
> diff --git a/drivers/iio/dac/ds4424.c b/drivers/iio/dac/ds4424.c
> new file mode 100644
> index 000000000000..d13590a00c79
> --- /dev/null
> +++ b/drivers/iio/dac/ds4424.c
> @@ -0,0 +1,733 @@
> +/*
> + * Maxim Integrated
> + * 7-bit, Multi-Channel Sink/Source Current DAC Driver
> + * Copyright (C) 2017 Maxim Integrated
> + *
> + * 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/kernel.h>
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/platform_device.h>
What are you using from platform_device? It's an i2c device
so I hope nothing!
> +#include <linux/regulator/consumer.h>
> +#include <linux/err.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/driver.h>
> +#include <linux/iio/machine.h>
> +#include <linux/iio/dac/ds4424.h>
> +
> +#define DS4424_DAC_ADDR(chan) ((chan) + 0xf8)
> +#define SOURCE_I 1
I'd like to see these prefixed with DS4424. Names
are a bit generic given they are rather specific.
> +#define SINK_I 0
> +
> +#define PWR_ON true
> +#define PWR_OFF false
It rather feels like, if these are needed, the
naming of what is being controlled isn't clear enough.
Given it's called enable, I think true is obvious enough.
> +
> +#define DS4424_CHANNEL(chan) { \
> + .type = IIO_CURRENT, \
> + .indexed = 1, \
> + .output = 1, \
> + .channel = chan, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> + BIT(IIO_CHAN_INFO_PROCESSED) | \
> + BIT(IIO_CHAN_INFO_SCALE),\
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET), \
> + .address = DS4424_DAC_ADDR(chan), \
Make spacing before \ consistent please.
> + .scan_type = { \
> + .sign = 'u', \
> + .realbits = 8, \
> + .storagebits = 8, \
> + .shift = 0, \
> + }, \
Hmm. slightly odd to see this here given mainline doesn't
currently support output buffers (which is what this is
describing).
> +}
> +
> +union raw_data {
It's a somewhat odd structure with a very generic name.
Name it ds4424_raw_data
> + struct {
> + u8 dx:7;
> + u8 source_bit:1; /* 1 is source, 0 is sink */
> + };
> + u8 bits;
> +};
> +
> +enum ds4424_device_ids {
> + ID_DS4422,
> + ID_DS4424,
> +};
> +
> +struct ds4424_data {
> + struct i2c_client *client;
> + struct mutex lock;
> + uint16_t raw[DS442X_MAX_DAC_CHANNELS];
> +#ifdef CONFIG_PM_SLEEP
> + uint16_t save[DS442X_MAX_DAC_CHANNELS];
> +#endif
Always nice to save space, but only if it doesn't add much
complexity. Not sure I'd bother with the ifdef on this one.
For PM functions for example, things are fiddly enough to
get right that generally the option is to mark them
__maybe_unused these days as that always works.

> + uint32_t max_rfs;
> + uint32_t min_rfs;
> + uint32_t ifs_scale;
> + uint32_t max_picoamp;
> + uint32_t rfs_res[DS442X_MAX_DAC_CHANNELS];
> + struct iio_map dac_iio_map[DS442X_MAX_DAC_CHANNELS + 1];
> + struct regulator *vcc_reg;
> + const char *vcc_reg_name;
> + bool regulator_state;
> +};
> +
> +static const struct ds4424_pdata ds4424_pdata_default = {
> + /* .vcc_supply_name = "dac_vdd_3v3", */
> + .min_rfs = 400,
> + .max_rfs = 1600,
> + .ifs_scale = 61000, /* 61000*100 = 6100000 = 100,000,000 * .976/16 */
> + .max_picoamp = 200000000,
> + .rfs_res = {400, 800, 1000, 1600},
> + .dac_iio_map = {
> + { .consumer_dev_name = "ds4424_dac-consumer-dev_name-1",
> + .consumer_channel = "ds4424_dac1",
> + .adc_channel_label = "OUT1"
A 'default' iio_map is an odd concept. Drop it. Makes no sense to me.
> + },
> + {
> + .consumer_dev_name = "ds4424_dac-consumer-dev_name-2",
> + .consumer_channel = "ds4424_dac2",
> + .adc_channel_label = "OUT2"
> + },
> + {
> + .consumer_dev_name = "ds4424_dac-consumer-dev_name-3",
> + .consumer_channel = "ds4424_dac3",
> + .adc_channel_label = "OUT3"
> + },
> + {
> + .consumer_dev_name = "ds4424_dac-consumer-dev_name-4",
> + .consumer_channel = "ds4424_dac4",
> + .adc_channel_label = "OUT4"
> + },
> + {},
> + },
> +};
> +
> +static const struct iio_chan_spec ds4424_channels[] = {
> + DS4424_CHANNEL(0),
> + DS4424_CHANNEL(1),
> + DS4424_CHANNEL(2),
> + DS4424_CHANNEL(3)
put the comma after the last one. General coding style point.
Not sure why we'd add more channels but perhaps there will be
an 8 channel version sometime in the future. Adding the comma
to the last line reduces churn on later patches.
> +};
> +
> +int ds4424_regulator_onoff(struct iio_dev *indio_dev, bool enable)
> +{
> + struct ds4424_data *data = iio_priv(indio_dev);
> + int ret = 0;
> +
> + if (data->vcc_reg == NULL)
> + return ret;
Having to keep track of the regulator state is unusual.
Let me see...

Nope, just checked all your call paths and there are no paths where
this is necessary. So drop this function and just call regulator_enable
/ regulator_disable in the appropriate places.

> +
> + if (data->regulator_state == PWR_OFF && enable == PWR_ON) {
> + ret = regulator_enable(data->vcc_reg);
> + if (ret) {
> + pr_err("%s - enable vcc_reg failed, ret=%d\n",
> + __func__, ret);
> + goto done;
> + }
> + } else if (data->regulator_state == PWR_ON && enable == PWR_OFF) {
> + ret = regulator_disable(data->vcc_reg);
> + if (ret) {
> + pr_err("%s - disable vcc_reg failed, ret=%d\n",
> + __func__, ret);
> + goto done;
> + }
> + }
> +
> + data->regulator_state = enable;
> +done:
> + return ret;
> +}
> +
> +static int ds4424_get_value(struct iio_dev *indio_dev,
> + int *val, int channel)
> +{
> + struct ds4424_data *data = iio_priv(indio_dev);
> + struct i2c_client *client = data->client;
This local variable doesn't really add anything and
slightly obscures what is going on. Just use data->client
at the call sites.
> + u8 outbuf[1];
> + u8 inbuf[1];
Why use arrays if they are always one element? Just
use the address of the u8 at call sites.
> + int ret;
> +
> + if ((channel < 0) && (channel >= indio_dev->num_channels))
> + return -EINVAL;
Overly paranoid. We have big problems if it's possible for the
channel number to be out of range!
> +
> + outbuf[0] = DS4424_DAC_ADDR(channel);
Looking very regmap or smbus register based...

Could you use the smbus_write_byte_data?
That is a lesser requirement in controller complexity than
supporting generic i2c so you'll increase the number of boards
this driver will work with.

Also 'might' allow you to drop the locks as the core will
serialise multiple smbus messages.
> + mutex_lock(&data->lock);
> + ret = i2c_master_send(client, outbuf, 1);
> + if (ret < 0) {
> + mutex_unlock(&data->lock);
> + return ret;
> + } else if (ret != 1) {
> + mutex_unlock(&data->lock);
> + return -EIO;
> + }
> +
> + ret = i2c_master_recv(client, inbuf, 1);
> + if (ret < 0) {
> + mutex_unlock(&data->lock);
> + return ret;
> + } else if (ret != 1) {
> + mutex_unlock(&data->lock);
> + return -EIO;
Standard trick is to move the mutex_unlock to after
the i2c_master_recv before checking the error.
Has to be in every path anyway.
> + }
> +
> + mutex_unlock(&data->lock);
> +
> + *val = inbuf[0];
> + return 0;
> +}
> +
> +/*
> + * DS4432 DAC control register 8 bits
> + * [7] 0: to sink; 1: to source
> + * [6:0] steps to sink/source
> + * bit[7] looks like a sign bit, but the value of the register is
> + * not a complemental code considering the bit[6:0] is a absolute
> + * distance from the zero point.
> + */
> +
> +/*
> + * val is positive if sourcing
> + * val is negative if sinking
> + * val can be -127 to 127
> + */
Try and use kernel-doc style for comments.
> +static int ds4424_set_value(struct iio_dev *indio_dev,
> + int val, struct iio_chan_spec const *chan)
> +{
> + struct ds4424_data *data = iio_priv(indio_dev);
> + struct i2c_client *client = data->client;
This local variable just obscures (ever so slightly) what is going
on. I'd just use it at the call sites.
> + u8 outbuf[2];
> + int ret;
> + int max_val = ((1 << chan->scan_type.realbits) - 1);
Given the driver currently only supports 8 bit devices, I'd
just put it in directly. Better to refactor the driver to
be more flexible when the need become obvious (i.e. when
adding non 8 bit device support).
> +
> + if (val < 0 || val > max_val)
> + return -EINVAL;
> +
> + if ((chan->channel < 0)
> + && (chan->channel >= indio_dev->num_channels))
> + return -EINVAL;
Again, I don't think this check can ever fail.
> +
> + outbuf[0] = DS4424_DAC_ADDR(chan->channel);
> + outbuf[1] = (val & 0xff);
Do you need the 0xff given you've checked the range?
> +
> + mutex_lock(&data->lock);
> + ret = i2c_master_send(client, outbuf, ARRAY_SIZE(outbuf));
smbus_write_byte_data will work with more controllers...
> + mutex_unlock(&data->lock);
> +
> + if (ret < 0)
> + return ret;
> + else if (ret >= 0 && ret != ARRAY_SIZE(outbuf))
> + return -EIO;
Added bonus of calling smbus_write_byte_data is that
it will always return error on failure rather than
a short write.
> +
> + data->raw[chan->channel] = outbuf[1];
This should probably be in the lock. Otherwise two
simultaneous writes could result in the stored value being
wrong.
> + return 0;
> +}
> +
> +static int ds4424_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + union raw_data raw;
> + int round_up, ret;
> + struct ds4424_data *data = iio_priv(indio_dev);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + /* Raw is processed a little bit
/*
* Raw

preferred for kernel comments in IIO (and most of the rest of
the kernel with a few notable exceptions!)
> + * outputs positive values for sourcing
> + * and negative values for sinking
Good - would be really odd to handle otherwise. This approach
is clean and easy to understand.
> + */
> + ret = ds4424_get_value(indio_dev, val, chan->channel);
> + if (ret < 0) {
> + pr_err("%s : ds4424_get_value returned %d\n",
> + __func__, ret);
> + return ret;
> + }
> + raw.bits = *val;
> + *val = raw.dx;
> + if (raw.source_bit == SINK_I)
> + *val = -*val;
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_PROCESSED:
A driver should not provide processed and raw values.
The only exceptions to this in tree are drivers which provided a wrong
implementation at some point in the past and ended up being ABI.

All this complexity is a job best done in userspace. That's more true
when streaming is involved (input devices only in mainline at the moment)
> + /**
> + * To get the processed current using the 8-bit raw data:
> + * bit 7 is a 1 if sourcing current and it's a 0 if sinking
> + * current.
> + * The current full scale (Ifs) depends on the Rfs resistor
> + * value in ohms:
> + * Ifs = (0.976/Rfs)*(127/16)
> + * Then the current sourced or sinked can be determined as
> + * follows:
> + * I = Ifs * (Dx/127)
> + * where Dx is the value of the seven bits 6 to 0.
> + */
> + if (data->rfs_res[chan->channel] < data->min_rfs ||
> + data->rfs_res[chan->channel] > data->max_rfs) {
> + pr_err("%s : rfs_res out of range. rfs_res[%d]: %d\n",
> + __func__,
> + chan->channel,
> + data->rfs_res[chan->channel]);
> + return -EINVAL;
> + }
> +
> + ret = ds4424_get_value(indio_dev, val, chan->channel);
> + if (ret < 0) {
> + pr_err("%s : ds4424_get_value returned %d\n",
> + __func__, ret);
> + return ret;
> + }
> + raw.bits = *val;
> + *val = data->ifs_scale * raw.dx * 100;
> + round_up = data->rfs_res[chan->channel] / 2;
> + *val = (*val + round_up) / data->rfs_res[chan->channel];
> +
> + if (raw.source_bit == SINK_I)
> + *val = -*val;
> + *val = *val * 100; /* picoAmps */
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_SCALE:
> + round_up = data->rfs_res[chan->channel] / 2;
> + /* picoAmps */
> + *val = (data->ifs_scale * 10000 + round_up) /
> + data->rfs_res[chan->channel];
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_OFFSET:
> + *val = 0;
> + return IIO_VAL_INT;
No need to provide an offset if it is 0. That's assumed to be
the default.
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +/**
> + * val is positive if sourcing
> + * val is negative if sinking
> + */
> +static int ds4424_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val, int val2, long mask)
> +{
> + union raw_data raw;
> + struct ds4424_data *data = iio_priv(indio_dev);
> + int val0, max_val, min_val, tmp_scale;
> +
> + if (val2 != 0)
> + return -EINVAL;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> +
> + max_val = ((1 << chan->scan_type.realbits)/2) - 1;
> + min_val = -max_val;
> + if ((val > max_val) || (val < min_val))
> + return -EINVAL;
> +
> + if (val > 0) {
> + raw.source_bit = SOURCE_I;
> + raw.dx = val;
> + } else {
> + raw.source_bit = SINK_I;
> + raw.dx = -val;
> + }
> +
> + return ds4424_set_value(indio_dev, raw.bits, chan);
> +
> + case IIO_CHAN_INFO_PROCESSED: /* val input is picoAmps */
Again, just provide the raw case. Userspace can deal with this.
> + /* val can be 0 to 200,000,000 (200 picoAmps) */
> + val0 = val;
> + raw.source_bit = SOURCE_I;
> + if (val < 0) {
> + raw.source_bit = SINK_I;
> + val = -val;
> + }
> + if (val > data->max_picoamp) {
> + pr_err("%s : Requested current %d ", __func__, val);
> + pr_err("exceeds %d picoAmps\n", data->max_picoamp);
> + return -EINVAL;
> + }
> + if (data->rfs_res[chan->channel] < data->min_rfs ||
> + data->rfs_res[chan->channel] > data->max_rfs) {
> + pr_info("%s : Resistor values out of range\n",
> + __func__);
> + return -EINVAL;
> + }
> + val = val / 1000;
> + tmp_scale = data->ifs_scale / 10; /* preserve resolution */
> + val = (val * data->rfs_res[chan->channel]) /
> + tmp_scale;
> + val = (val + 50) / 100;
> + val2 = ((1 << chan->scan_type.realbits) / 2) - 1;
> + if (val > val2) {
> + pr_info("%s : Requested current %d %d",
> + __func__, val0, val);
> + pr_info("exceeds maximum. DAC set to maximum %d\n",
> + val2);
> + val = val2;
> + }
> + raw.dx = val;
> + return ds4424_set_value(indio_dev, raw.bits, chan);
> +
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int ds4424_verify_chip(struct iio_dev *indio_dev)
> +{
> + int ret = 0, val;
> + int i;
> +
Document the 'why' of this. I'm guessing this is a delay after
potential regulator enable? If so would be more logical
to stick it after then regulator_enable rather than before
what comes next.
> + usleep_range(1000, 1200);
> + for (i = 0; i < indio_dev->num_channels; i++) {
> + ret = ds4424_get_value(indio_dev, &val, i);
> + if (ret < 0) {
> + pr_err("%s : read %d, should be 0\n", __func__, ret);
> + break;
> + }
I'd like to see a comment explaining what this is testing.
From the error I assumed it was the reset value (note a probe / remove / probe
sequence would have broken that if a fixed regulator was supplying VCC).
However, you are printing the return value not the value being read.

Hence I'm confused and this needs clarifying.
> + }
> + return ret;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
There are all sorts of fiddly cases in the PM code
that mean there is a general move to not use the
ifdefs but instead just mark the functions
__maybe_unused
> +static int ds4424_suspend(struct device *dev)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct ds4424_data *data = iio_priv(indio_dev);
> + int ret = 0;
> + u32 i;
> +
> + for (i = 0; i < indio_dev->num_channels; i++) {
> + data->save[i] = data->raw[i];
> + ret = ds4424_set_value(indio_dev, 0,
> + &(indio_dev->channels[i]));
> + if (ret < 0)
> + return ret;
> + }
> + return ret;
> +}
> +
> +static int ds4424_resume(struct device *dev)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct ds4424_data *data = iio_priv(indio_dev);
> + int ret = 0;
> + u32 i;
> +
> + for (i = 0; i < indio_dev->num_channels; i++) {
> + ret = ds4424_set_value(indio_dev, data->save[i],
> + &(indio_dev->channels[i]));
> + if (ret < 0)
> + return ret;
> + }
> + return ret;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(ds4424_pm_ops, ds4424_suspend, ds4424_resume);
> +#define DS4424_PM_OPS (&ds4424_pm_ops)
> +#else
> +#define DS4424_PM_OPS NULL
> +#endif /* CONFIG_PM_SLEEP */
> +
> +static const struct iio_info ds4424_info = {
> + .read_raw = ds4424_read_raw,
> + .write_raw = ds4424_write_raw,
> + .driver_module = THIS_MODULE,
Just for reference, I'm working on a set that will
remove the necessity to explicitly supply .driver_module.
Might cause merge issues depending on whether it beats this
driver in or not.
> +};
> +
> +#ifdef CONFIG_OF
> +static int ds4424_parse_dt(struct iio_dev *indio_dev)
> +{
> + int ret;
> + int len;
> + int num_ch;
> + int i;
> + int count;
> + struct property *prop;
> + struct ds4424_data *data = iio_priv(indio_dev);
> + struct device_node *node = indio_dev->dev.parent->of_node;
Usual method for this is to set indio_dev->dev.of_node to the parent of_node
before calling any parsing code.
> +
> + if (!node) {
> + pr_info("%s:%d ds4424 dts not found\n", __func__, __LINE__);
> + return -ENODEV;
> + }
> +
> + prop = of_find_property(node, "rfs-resistors", &len);
> + if (!prop) {
> + pr_err("Invalid rfs-resistor in dt. len: %d\n", len);
> + return -EINVAL;
> + }
> +
> + if (len != (DS442X_MAX_DAC_CHANNELS * sizeof(uint32_t))) {
> + pr_err("Invalid rfs-resistor length in dt. len: %d\n", len);
> + return -EINVAL;
> + }
> +
> + ret = of_property_read_u32_array(node, "rfs-resistors",
> + data->rfs_res, DS442X_MAX_DAC_CHANNELS);
> + if (ret < 0) {
> + pr_err("Reading rfs-resistors from dt failed. ret: %d\n", ret);
> + return ret;
> + }
> +
> + pr_info("ds4424 rfs-resistors: %d, %d, %d, %d\n",
> + data->rfs_res[0], data->rfs_res[1],
> + data->rfs_res[2], data->rfs_res[3]);
> +
> + ret = of_property_read_u32(node, "max-rfs",
> + &data->max_rfs);
> + if (ret < 0) {
> + pr_err("Reading max-rfs from dt failed. ret: %d\n", ret);
> + return ret;
> + }
> +
> + ret = of_property_read_u32(node, "min-rfs",
> + (u32 *)&data->min_rfs);
> + if (ret < 0) {
> + pr_err("Reading min-rfs from dt failed. ret: %d\n", ret);
> + return ret;
> + }
> +
> + pr_info("ds4424 max-rfs: %d, min-rfs: %d\n",
> + data->max_rfs, data->min_rfs);
> +
> + ret = of_property_read_u32(node, "max-picoamp",
> + (u32 *)&data->max_picoamp);
> + if (ret < 0) {
> + pr_err("Reading max-picoamp from dt failed. ret: %d\n", ret);
> + return ret;
> + }
> +
> + ret = of_property_read_u32(node, "ifs-scale",
> + (u32 *)&data->ifs_scale);
> + if (ret < 0) {
> + pr_err("Reading ifs-scale from dt failed. ret: %d\n", ret);
> + return ret;
> + }
> +
> + pr_info("ds4424 max-picoamp: %d, ifs-scale: %d\n",
> + data->max_picoamp, data->ifs_scale);
> +
> + count = of_property_count_strings(node, "dac-iio-map");
> + if (count < 0) {
> + pr_info("dac-iio-map not found in dts\n");
> + return count;
> + }
> +
> + ret = of_property_read_string(node, "vcc-supply", &data->vcc_reg_name);
> + if (ret < 0) {
> + pr_info("DAC vcc-supply is not available in dts\n");
> + data->vcc_reg_name = NULL;
> + }
> +
> + if (count != DS4424_MAX_DAC_CHANNELS * 3 &&
> + count != DS4424_MAX_DAC_CHANNELS * 3) {
> + pr_info("Incorrect dac-iio-map in dts. count: %d\n", count);
> + return -EINVAL;
> + }
> +
> + num_ch = count / 3;
> + for (i = 0; i < num_ch; i++) {
> + ret = of_property_read_string_index(node,
> + "dac-iio-map", i * 3,
> + &data->dac_iio_map[i].consumer_dev_name);
> + if (ret < 0) {
> + pr_info("%s:%d\n", __func__, __LINE__);
> + return ret;
> + }
> +
> + ret = of_property_read_string_index(node, "dac-iio-map",
> + i * 3 + 1,
> + &data->dac_iio_map[i].consumer_channel);
> + if (ret < 0) {
> + pr_info("%s:%d\n", __func__, __LINE__);
> + return ret;
> + }
> +
> + ret = of_property_read_string_index(node, "dac-iio-map",
> + i * 3 + 2,
> + &data->dac_iio_map[i].adc_channel_label);
> + if (ret < 0) {
> + pr_info("%s:%d\n", __func__, __LINE__);
> + return ret;
> + }
> +
> + pr_info("ds4424 iio-map[%d]: %s, %s, %s\n", i,
> + data->dac_iio_map[i].consumer_dev_name,
> + data->dac_iio_map[i].consumer_channel,
> + data->dac_iio_map[i].adc_channel_label);
> + }
> +
> + return 0;
> +}
> +#else
> +static int ds4424_parse_dt(struct iio_dev *indio_dev)
> +{
> + return -ENODEV;
> +}
> +#endif
> +
> +static int ds4424_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + const struct ds4424_pdata *pdata;
> + struct ds4424_data *data;
> + struct iio_dev *indio_dev;
> + int ret;
> +
> + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> + dev_err(&client->dev, "I2C is not supported\n");
> + return -ENODEV;
> + }
As observed above, I think all your calls are actually
smbus_write/read_byte_data so this requirement may we be more relaxed.
> +
> + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> + if (!indio_dev) {
> + pr_err("%s:%d\n", __func__, __LINE__);
> + return -ENOMEM;
> + }
> +
> + data = iio_priv(indio_dev);
> + memset(data, 0, sizeof(*data));
Unnecessary memset - take a look in the iio_device_alloc call, uses
kzalloc.

> + i2c_set_clientdata(client, indio_dev);
> + data->client = client;
> + indio_dev->name = id->name;
> + indio_dev->dev.parent = &client->dev;
> +
> + ret = ds4424_verify_chip(indio_dev);
> + if (ret < 0) {
> + dev_err(&client->dev, "%s failed. ret:%d\n", __func__, ret);
> + return -ENXIO;
> + }
> +
> + if (client->dev.of_node) {
> + ret = ds4424_parse_dt(indio_dev);
> + if (ret < 0) {
> + dev_err(&client->dev,
> + "%s - of_node error\n", __func__);
> + ret = -EINVAL;
> + }
> + } else {
> + pdata = client->dev.platform_data;
> + if (!pdata) {
> + dev_err(&client->dev,
> + "dts/platform data not found.\n");
> + /* Use default driver settings */
> + pdata = &ds4424_pdata_default;
> + }
> +
> + pdata = client->dev.platform_data;
> + data->min_rfs = pdata->min_rfs;
> + data->max_rfs = pdata->max_rfs;
> + data->ifs_scale = pdata->ifs_scale;
> + data->max_picoamp = pdata->max_picoamp;
> + data->vcc_reg_name = pdata->vcc_supply_name;
> + memcpy(data->rfs_res, pdata->rfs_res,
> + sizeof(uint32_t) * DS442X_MAX_DAC_CHANNELS);
> + memcpy(data->dac_iio_map, pdata->dac_iio_map,
> + sizeof(struct iio_map) * DS442X_MAX_DAC_CHANNELS);
> + }
> +
> + if (data->vcc_reg_name) {
> + data->vcc_reg = devm_regulator_get(&client->dev,
> + data->vcc_reg_name);
> + if (IS_ERR(data->vcc_reg)) {
> + ret = PTR_ERR(data->vcc_reg);
> + dev_err(&client->dev,
> + "Failed to get vcc_reg regulator: %d\n", ret);
> + return ret;
> + }
> + }
> +
> + mutex_init(&data->lock);
> + ret = ds4424_regulator_onoff(indio_dev, PWR_ON);
> + if (ret < 0) {
> + pr_err("Unable to turn on the regulator. %s:%d, ret: %d\n",
> + __func__, __LINE__, ret);
> + return ret;
> + }
> +
> + switch (id->driver_data) {
> + case ID_DS4422:
> + indio_dev->num_channels = DS4422_MAX_DAC_CHANNELS;
> + break;
> + case ID_DS4424:
> + indio_dev->num_channels = DS4424_MAX_DAC_CHANNELS;
> + break;
> + default:
Fault on this. No way of knowing what is going on so we shouldn't
guess.
> + indio_dev->num_channels = DS4424_MAX_DAC_CHANNELS;
> + break;
> + }
> +
> + indio_dev->channels = ds4424_channels;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->info = &ds4424_info;
> +
> + ret = iio_map_array_register(indio_dev, data->dac_iio_map);
> + if (ret < 0)
> + goto err_iio_device_0;
Please use meaningful labels rather than numeric ones. Numeric
ones just cause churn as a driver changes.
> +
> + ret = iio_device_register(indio_dev);
> + if (ret < 0) {
> + pr_err("iio_device_register failed . %s:%d, ret: %d\n",
> + __func__, __LINE__, ret);
> + goto err_iio_device_1;
> + }
> +
> + return ret;
> +
> +err_iio_device_0:
> + ds4424_regulator_onoff(indio_dev, PWR_OFF);
> +err_iio_device_1:
> + iio_map_array_unregister(indio_dev);
> + return ret;
> +}
> +
> +static int ds4424_remove(struct i2c_client *client)
> +{
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +
> + iio_device_unregister(indio_dev);
> + iio_map_array_unregister(indio_dev);
> + ds4424_regulator_onoff(indio_dev, PWR_OFF);
nitpick: blank line here.
> + return 0;
> +}
> +
> +static const struct i2c_device_id ds4424_id[] = {
> + { "ds4422", ID_DS4422 },
> + { "ds4424", ID_DS4424 },
> + { }
> +};
> +MODULE_DEVICE_TABLE(i2c, ds4424_id);
> +
> +static const struct of_device_id ds4424_of_match[] = {
> + { .compatible = "maxim,ds4422" },
> + { .compatible = "maxim,ds4424" },
> + { }
> +};
> +
> +MODULE_DEVICE_TABLE(of, ds4424_of_match);
> +
> +static struct i2c_driver ds4424_driver = {
> + .driver = {
> + .name = "ds4424",
> + .pm = DS4424_PM_OPS,
> + },
> + .probe = ds4424_probe,
> + .remove = ds4424_remove,
> + .id_table = ds4424_id,
> +};
> +module_i2c_driver(ds4424_driver);
> +
> +MODULE_DESCRIPTION("Maxim DS4424 DAC Driver");
> +MODULE_AUTHOR("Ismail H. Kose <ismail.kose@maximintegrated.com>");
> +MODULE_AUTHOR("Vishal Sood <vishal.sood@maximintegrated.com>");
> +MODULE_AUTHOR("David Jung <david.jung@maximintegrated.com>");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/iio/dac/ds4424.h b/include/linux/iio/dac/ds4424.h
> new file mode 100644
> index 000000000000..09ff3d61797d
> --- /dev/null
> +++ b/include/linux/iio/dac/ds4424.h
> @@ -0,0 +1,29 @@
> +/*
> + * Maxim Integrated
> + * 7-bit, Multi-Channel Sink/Source Current DAC Driver
> + * Copyright (C) 2017 Maxim Integrated
> + *
> + * 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.
> + */
> +
> +#ifndef IIO_DAC_DS4424_H_
> +#define IIO_DAC_DS4424_H_
> +#include <linux/iio/iio.h>
> +#include <linux/iio/machine.h>
> +
> +#define DS4422_MAX_DAC_CHANNELS 2
> +#define DS4424_MAX_DAC_CHANNELS 4
> +#define DS442X_MAX_DAC_CHANNELS DS4424_MAX_DAC_CHANNELS
> +
> +struct ds4424_pdata {
> + const char *vcc_supply_name;
> + uint32_t max_rfs;
> + uint32_t min_rfs;
As with the devicetree some of these are characteristics of the
device being supported rather than the board implementing it
(feel free to persuade me otherwise!) so shouldn't be here.
> + uint32_t ifs_scale;
> + uint32_t max_picoamp;
> + uint32_t rfs_res[DS442X_MAX_DAC_CHANNELS];
> + struct iio_map dac_iio_map[DS442X_MAX_DAC_CHANNELS + 1];
> +};
> +#endif /* IIO_DAC_DS4424_H_ */

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