Re: [PATCH v6 1/2] iio: dac: ds4422/ds4424 dac driver

From: Jonathan Cameron
Date: Sun Sep 24 2017 - 10:46:00 EST

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On Fri, 22 Sep 2017 13:12:08 -0700
"Ismail H. Kose" <Ismail.Kose@xxxxxxxxxxxxxxxxxxx> wrote:

> This patch provides an iio device driver for DS4422/DS4424 chips that support
> two/four channel 7-bit Sink/Source Current DAC.
>
> Signed-off-by: Ismail H. Kose <Ismail.Kose@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ismail H. Kose <ihkose@xxxxxxxxx>

A few minor comments inline. This is coming together nicely.

Jonathan

> ---
> v6:
> * Removed reference resistor parsing
> v5:
> * Removed unused variable
> v4:
> * Removed unnecessary code and space optimization
> * Alphabetic order in Kconfig and Makefile
> v3:
> * Removed iio-map and platform file support
> * Removed ds4424.h file
> * Fixed ADC value read bug
> * Removed confused comments
> * Added device tree binding file
> * Fixed bugs in probe and read function
> v2:
> * Fixed coding style and removed unncessary code
> * Removed min/max rfs, ifs-scale, etc values from device tree
> * Removed unused code, definitions and some comments
> * Removed regulator control and made standard structure
> * Removed data processing and channel scale
> * Removed device tree binding file
>
> drivers/iio/dac/Kconfig | 9 ++
> drivers/iio/dac/Makefile | 1 +
> drivers/iio/dac/ds4424.c | 340 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 350 insertions(+)
> create mode 100644 drivers/iio/dac/ds4424.c
>
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 25bed2d7d2b9..57c179830981 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -211,6 +211,15 @@ config AD8801
> To compile this driver as a module choose M here: the module will be called
> ad8801.
>
> +config DS4424
> + tristate "Maxim Integrated DS4422/DS4424 DAC driver"
> + depends on I2C
> + help
> + If you say yes here you get support for Maxim chips DS4422, DS4424.
> +
> + This driver can also be built as a module. If so, the module
> + will be called ds4424.
> +
> config DPOT_DAC
> tristate "DAC emulation using a DPOT"
> depends on OF
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index 603587cc2f07..abf5c3094454 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -22,6 +22,7 @@ obj-$(CONFIG_AD5686) += ad5686.o
> obj-$(CONFIG_AD7303) += ad7303.o
> obj-$(CONFIG_AD8801) += ad8801.o
> obj-$(CONFIG_CIO_DAC) += cio-dac.o
> +obj-$(CONFIG_DS4424) += ds4424.o
> obj-$(CONFIG_DPOT_DAC) += dpot-dac.o
> obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
> obj-$(CONFIG_LTC2632) += ltc2632.o
> diff --git a/drivers/iio/dac/ds4424.c b/drivers/iio/dac/ds4424.c
> new file mode 100644
> index 000000000000..aea0cd12f9b8
> --- /dev/null
> +++ b/drivers/iio/dac/ds4424.c
> @@ -0,0 +1,340 @@
> +/*
> + * 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/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/consumer.h>
> +
> +#define DS4422_MAX_DAC_CHANNELS 2
> +#define DS4424_MAX_DAC_CHANNELS 4
> +
> +#define DS4424_DAC_ADDR(chan) ((chan) + 0xf8)
> +#define DS4424_SOURCE_I 1
> +#define DS4424_SINK_I 0
> +
> +#define DS4424_CHANNEL(chan) { \
> + .type = IIO_CURRENT, \
> + .indexed = 1, \
> + .output = 1, \
> + .channel = chan, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> +}
> +
> +/*
> + * DS4424 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 two's complement code considering the bit[6:0] is a absolute
> + * distance from the zero point.
> + */
> +union ds4424_raw_data {
> + struct {
> + u8 dx:7;
> + u8 source_bit:1;
> + };
> + u8 bits;
> +};
> +
> +enum ds4424_device_ids {
> + ID_DS4422,
> + ID_DS4424,
> +};
> +
> +struct ds4424_data {
> + struct i2c_client *client;
> + struct mutex lock;
> + __maybe_unused uint8_t save[DS4424_MAX_DAC_CHANNELS];
> + struct regulator *vcc_reg;
> + uint8_t raw[DS4424_MAX_DAC_CHANNELS];
> +};
> +
> +static const struct iio_chan_spec ds4424_channels[] = {
> + DS4424_CHANNEL(0),
> + DS4424_CHANNEL(1),
> + DS4424_CHANNEL(2),
> + DS4424_CHANNEL(3),
> +};
> +
> +static int ds4424_get_value(struct iio_dev *indio_dev,
> + int *val, int channel)
> +{
> + struct ds4424_data *data = iio_priv(indio_dev);
> + int ret;
> +
> + mutex_lock(&data->lock);
> + ret = i2c_smbus_read_byte_data(data->client, DS4424_DAC_ADDR(channel));
> + if (ret < 0)
> + goto fail;
> +
> + *val = ret;
> + mutex_unlock(&data->lock);
> + return 0;

Lose previous two lines and use the logic in the error path.

> +
> +fail:
> + mutex_unlock(&data->lock);
> + return ret;
> +}
> +
> +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);
> + int ret;
> +
> + mutex_lock(&data->lock);
> + ret = i2c_smbus_write_byte_data(data->client,
> + DS4424_DAC_ADDR(chan->channel), val);
> + if (ret < 0) {
> + mutex_unlock(&data->lock);

A goto unlock: would be slightly cleaner.

> + return ret;
> + }
> +
> + data->raw[chan->channel] = val;
> + mutex_unlock(&data->lock);
> +
> + 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 ds4424_raw_data raw;
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + 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 == DS4424_SINK_I)
> + *val = -*val;
> + return IIO_VAL_INT;
> +
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int ds4424_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val, int val2, long mask)
> +{
> + union ds4424_raw_data raw;
> +
> + if (val2 != 0)
> + return -EINVAL;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + if (val < S8_MIN || val > S8_MAX)
> + return -EINVAL;
> +
> + if (val > 0) {
> + raw.source_bit = DS4424_SOURCE_I;
> + raw.dx = val;
> + } else {
> + raw.source_bit = DS4424_SINK_I;
> + 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, val;
> +
> + ret = ds4424_get_value(indio_dev, &val, DS4424_DAC_ADDR(0));
> + if (ret < 0)
> + dev_err(&indio_dev->dev,
> + "%s failed. ret: %d\n", __func__, ret);
> +
> + return ret;
> +}
> +
> +static int __maybe_unused 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;
> + int 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 __maybe_unused 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;
> + int 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);
> +
> +static const struct iio_info ds4424_info = {
> + .read_raw = ds4424_read_raw,
> + .write_raw = ds4424_write_raw,
> +};
> +
> +static int ds4424_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct ds4424_data *data;
> + struct iio_dev *indio_dev;
> + int ret;
> +
> + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> + if (!indio_dev) {
> + dev_err(&client->dev, "iio dev alloc failed.\n");
> + return -ENOMEM;
> + }
> +
> + data = iio_priv(indio_dev);
> + i2c_set_clientdata(client, indio_dev);
> + data->client = client;
> + indio_dev->name = id->name;
> + indio_dev->dev.of_node = client->dev.of_node;
> + indio_dev->dev.parent = &client->dev;
> +
> + if (!client->dev.of_node) {
> + dev_err(&client->dev,
> + "Not found DT.\n");
> + return -EPERM;

Slightly odd error. -ENODEV probably makes more sense...

> + }
> +
> + data->vcc_reg = devm_regulator_get(&client->dev, "vcc");
> + if (IS_ERR(data->vcc_reg)) {
> + ret = PTR_ERR(data->vcc_reg);
> + dev_err(&client->dev,
> + "Failed to get vcc-supply regulator: %d\n", ret);
> + return ret;

return PTR_ERR(data->vcc_reg);

> + }
> +
> + mutex_init(&data->lock);
> + ret = regulator_enable(data->vcc_reg);
> + if (ret < 0) {
> + dev_err(&client->dev,
> + "Unable to enable the regulator.\n");
> + return ret;
> + }
> +
> + usleep_range(1000, 1200);
> + ret = ds4424_verify_chip(indio_dev);
> + if (ret < 0)

regulator disable? Easier if you do a goto block at the end
for any error handling which is not a valid direct return
(see below).

> + return -ENXIO;
> +
> + 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:
> + dev_err(&client->dev,
> + "ds4424: Invalid chip id.\n");
> + regulator_disable(data->vcc_reg);

Given you have multiple error paths where regulator_disable is needed,
I would prefer this done as a goto with the error handling laid
out at the end of this function rather than mutiple copies inline.

> + return -ENXIO;
> + }
> +
> + indio_dev->channels = ds4424_channels;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->info = &ds4424_info;
> +
> + ret = iio_device_register(indio_dev);
> + if (ret < 0) {
> + dev_err(&client->dev,
> + "iio_device_register failed. ret: %d\n", ret);
> + regulator_disable(data->vcc_reg);
> + }
> +
> + return ret;
> +}
> +
> +static int ds4424_remove(struct i2c_client *client)
> +{
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct ds4424_data *data = iio_priv(indio_dev);
> +
> + iio_device_unregister(indio_dev);
> + regulator_disable(data->vcc_reg);
> +
> + 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",
> + .of_match_table = ds4424_of_match,
> + .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@xxxxxxxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Vishal Sood <vishal.sood@xxxxxxxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("David Jung <david.jung@xxxxxxxxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");

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