Re: [RCF 1/3] hwmon: Add ads1118 driver

Re: [RCF 1/3] hwmon: Add ads1118 driver

[Guenter Roeck]

On 07/15/2016 05:18 PM, Joshua Clayton wrote:
> Add new driver for Texas Instruments ADS1118 and and ADS1018.
> This driver works with ADS1018, because of code borrowed
> from asd1015, which is similar, but I can only test ADS1118
>

Browsing through the datasheet, I think this should probably be implemented
as iio driver (and iio already has a driver for ads1015).

Jonathan, what do you think ?

Thanks,
Guenter

> Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
> ---
>   drivers/hwmon/Kconfig   |  11 ++
>   drivers/hwmon/Makefile  |   1 +
>   drivers/hwmon/ads1118.c | 516 ++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 528 insertions(+)
>   create mode 100644 drivers/hwmon/ads1118.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index ff94007..cadde38 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1459,6 +1459,17 @@ config SENSORS_ADS1015
>   	  This driver can also be built as a module.  If so, the module
>   	  will be called ads1015.
>
> +config SENSORS_ADS1118
> +	tristate "Texas Instruments ADS1018/ADS1118"
> +	depends on SPI
> +	help
> +	  If you say yes here you get support for Texas Instruments
> +	  ADS1118 16-bit 4-input ADC device and temperature sensor,
> +	  and the 12-bit ADS1018.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called ads1118.
> +
>   config SENSORS_ADS7828
>   	tristate "Texas Instruments ADS7828 and compatibles"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 2ef5b7c..a3b4b2e 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_SENSORS_ADM1029)	+= adm1029.o
>   obj-$(CONFIG_SENSORS_ADM1031)	+= adm1031.o
>   obj-$(CONFIG_SENSORS_ADM9240)	+= adm9240.o
>   obj-$(CONFIG_SENSORS_ADS1015)	+= ads1015.o
> +obj-$(CONFIG_SENSORS_ADS1118)	+= ads1118.o
>   obj-$(CONFIG_SENSORS_ADS7828)	+= ads7828.o
>   obj-$(CONFIG_SENSORS_ADS7871)	+= ads7871.o
>   obj-$(CONFIG_SENSORS_ADT7X10)	+= adt7x10.o
> diff --git a/drivers/hwmon/ads1118.c b/drivers/hwmon/ads1118.c
> new file mode 100644
> index 0000000..65ee337
> --- /dev/null
> +++ b/drivers/hwmon/ads1118.c
> @@ -0,0 +1,516 @@
> +/*
> + * ads1118.c - hwmon driver for Texas Instruments ADS1118 16-bit 4-input ADC
> + * / temperature sensor, and Texas Instruments ADS1018, a faster, 12-bit
> + * chip  of the same family.
> + *
> + * Author: Joshua Clayton
> + *
> + * Loosely based on ads1015.c by Dirk Eibach and others
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/delay.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/err.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/spi/spi.h>
> +
> +struct ads_table {
> +	unsigned int rates[8];
> +	unsigned int divisor;
> +};
> +
> +struct ads_channel {
> +	unsigned int delay_ms;
> +	int pga;
> +	u16 cfg;
> +	bool enabled;
> +};
> +
> +/* PGA fullscale voltages in microvolts */
> +static const unsigned int fullscale_table[8] = {
> +	6144000, 4096000, 2048000, 1024000, 512000, 256000, 256000, 256000 };
> +
> +static const struct ads_table ads1018_table = {
> +	.rates = {128, 250, 490, 920, 1600, 2400, 3300, 3300},
> +	.divisor = 0x7ff0,
> +};
> +
> +static const struct ads_table ads1118_table = {
> +	.rates = {8, 16, 32, 64, 128, 250, 475, 860},
> +	.divisor = 0x7fff,
> +};
> +
> +#define ADS1118_NUM_CHANS 5
> +#define ADS1118_TEMP_CHAN 4
> +
> +struct ads1118 {
> +	struct device *hwmon_dev;
> +	struct device *dev;
> +	struct mutex update_lock; /* mutex protect updates */
> +	struct ads_channel channel_data[ADS1118_NUM_CHANS];
> +	const struct ads_table *ref;
> +};
> +
> +/*
> + * NOTE: the bit offsets in the datasheet are 16 bit big
> + * endian. I've swapped upper and lower bytes in the defines
> + * so no twiddling is needed when sending the cfg to the device.
> + */
> +#define ADS1118_MODE	0	/* single shot mode */
> +#define ADS1118_PGA	1	/* programmmed gain */
> +#define ADS1118_MUX	4	/* input channel */
> +#define ADS1118_SS	7	/* start a conversion */
> +#define ADS1118_NOP	8	/* validation pattern */
> +#define ADS1118_PULL_UP	11	/* pullup resistor on MISO */
> +#define ADS1118_TS_MODE	12	/* temperature sensor mode */
> +#define ADS1118_DR	13	/* data rate table index */
> +
> +#define ADS1118_ADC_CFG (BIT(ADS1118_MODE) | BIT(ADS1118_SS) | \
> +		(0x3 << ADS1118_NOP) | BIT(ADS1118_PULL_UP))
> +#define ADS1118_TEMP_CFG (ADS1118_ADC_CFG | BIT(ADS1118_TS_MODE))
> +
> +/* MUX values for AINN (second input or ground) */
> +#define ADS1118_MUX_AINN1 0
> +#define ADS1118_MUX_AINN3 1
> +#define ADS1118_MUX_AINN_GND 4
> +
> +#define ADS1118_DEFAULT_PGA 0
> +#define ADS1118_DEFAULT_DR 7
> +
> +static inline void ads1118_set_cfg(u16 *cfg, u16 value, int offset)
> +{
> +	*cfg &= ~(0x07 << offset);
> +	*cfg |= ((value & 0x07) << offset);
> +}
> +
> +static int ads1118_channel_set_pga(struct ads_channel *chan, u32 fullscale)
> +{
> +	int i;
> +
> +	for (i = 7; i >= 0; --i)
> +		if (fullscale_table[i] == fullscale)
> +			break;
> +
> +	if (i < 0)
> +		return -EINVAL;
> +
> +	chan->pga = fullscale / 1000;
> +	ads1118_set_cfg(&chan->cfg, i, ADS1118_PGA);
> +
> +	return 0;
> +}
> +
> +static int ads1118_chan_set_mux(struct ads_channel *chan, u16 in1, u16 in2)
> +{
> +	switch (in1) {
> +	case 0:
> +		if (in2 == ADS1118_MUX_AINN1)
> +			break;
> +	case 1:
> +	case 2:
> +		if (in2 == ADS1118_MUX_AINN3)
> +			break;
> +	case 3:
> +		if (in2 == ADS1118_MUX_AINN_GND)
> +			break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	ads1118_set_cfg(&chan->cfg, in1 + in2, ADS1118_MUX);
> +
> +	return 0;
> +}
> +
> +static int ads1118_chan_set_rate(struct ads1118 *ads,
> +				 struct ads_channel *chan, u32 rate)
> +{
> +	int i;
> +
> +	for (i = 7; i >= 0; --i)
> +		if (ads->ref->rates[i] == rate)
> +			break;
> +
> +	if (i < 0)
> +		return -EINVAL;
> +
> +	chan->delay_ms = DIV_ROUND_UP(1000, rate);
> +	ads1118_set_cfg(&chan->cfg, i, ADS1118_DR);
> +
> +	return 0;
> +}
> +
> +static int ads1118_read_adc(struct ads1118 *ads, struct ads_channel *chan,
> +			    s16 *value)
> +{
> +	int ret;
> +	u16 buf;
> +	struct spi_device *spi = to_spi_device(ads->dev);
> +
> +	mutex_lock(&ads->update_lock);
> +
> +	ret = spi_write(spi, &chan->cfg, sizeof(chan->cfg));
> +	if (ret < 0)
> +		goto err_unlock;
> +
> +	/* wait until conversion finished */
> +	msleep(chan->delay_ms);
> +
> +	ret = spi_read(spi, &buf, sizeof(buf));
> +	if (ret)
> +		dev_info(&spi->dev, "error reading: %d\n", ret);
> +
> +	*value = (s16)be16_to_cpu(buf);
> +
> +err_unlock:
> +	mutex_unlock(&ads->update_lock);
> +	return ret;
> +}
> +
> +static ssize_t show_in(struct device *dev, struct device_attribute *da,
> +	char *buf)
> +{
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +	struct ads1118 *ads = dev_get_drvdata(dev);
> +	struct ads_channel *chan = &ads->channel_data[attr->index];
> +	s16 read_value;
> +	int microvolts;
> +	int ret;
> +
> +	ret = ads1118_read_adc(ads, chan, &read_value);
> +	if (ret < 0)
> +		return ret;
> +
> +	microvolts = DIV_ROUND_CLOSEST(read_value * chan->pga,
> +				       ads->ref->divisor);
> +
> +	return sprintf(buf, "%d\n", microvolts);
> +}
> +
> +static ssize_t show_temp(struct device *dev, struct device_attribute *da,
> +			 char *buf)
> +{
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +	struct ads1118 *ads = dev_get_drvdata(dev);
> +	struct ads_channel *chan = &ads->channel_data[attr->index];
> +	s16 read_value;
> +	int ret;
> +
> +	ret = ads1118_read_adc(ads, chan, &read_value);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * The ads1118 datasheet indicates 32nds of degree steps, but
> +	 * 14 bits left justified means a divisor of 128.
> +	 */
> +	return sprintf(buf, "%d\n", (((int)read_value) * 1000) >> 7);
> +}
> +
> +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_in, NULL, 0);
> +static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_in, NULL, 1);
> +static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_in, NULL, 2);
> +static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_in, NULL, 3);
> +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL,
> +		ADS1118_TEMP_CHAN);
> +
> +static struct attribute *ads1118_attributes[] = {
> +	&sensor_dev_attr_in0_input.dev_attr.attr,
> +	&sensor_dev_attr_in1_input.dev_attr.attr,
> +	&sensor_dev_attr_in2_input.dev_attr.attr,
> +	&sensor_dev_attr_in3_input.dev_attr.attr,
> +
> +	&sensor_dev_attr_temp1_input.dev_attr.attr,
> +	NULL
> +};
> +
> +static umode_t ads1118_attrs_visible(struct kobject *kobj,
> +				     struct attribute *attr, int n)
> +{
> +	struct device *dev = container_of(kobj, struct device, kobj);
> +	struct ads1118 *ads = dev_get_drvdata(dev);
> +
> +	if (ads->channel_data[n].enabled)
> +		return attr->mode;
> +
> +	return 0;
> +}
> +
> +static const struct attribute_group ads1118_attr_group = {
> +	.attrs = ads1118_attributes,
> +	.is_visible = ads1118_attrs_visible,
> +};
> +
> +static const struct attribute_group *groups[] = {
> +	&ads1118_attr_group,
> +	NULL
> +};
> +
> +#ifdef CONFIG_OF
> +static int ads1118_of_get_chan(struct device *dev, struct device_node *node)
> +{
> +	u32 chan_i;
> +
> +	if (!of_device_is_available(node))
> +		return -EINVAL;
> +
> +	if (of_property_read_u32(node, "reg", &chan_i)) {
> +		dev_err(dev, "reg value missing in %s\n", node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	if (chan_i >= ADS1118_TEMP_CHAN) {
> +		dev_err(dev, "reg value %d out of range in %s\n",
> +				chan_i, node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	return (int)chan_i;
> +}
> +
> +static int ads1118_of_get_chan_pga(struct device *dev,
> +				   struct device_node *node,
> +				   struct ads_channel *chan)
> +{
> +	int ret;
> +	u32 fullscale;
> +
> +	ret = of_property_read_u32(node, "ti,fullscale", &fullscale);
> +	if (ret == -EINVAL) {
> +		fullscale = fullscale_table[ADS1118_DEFAULT_PGA];
> +	} else if (ret) {
> +		dev_err(dev, "bad ti,fullscale on %s: should be u32\n",
> +			node->full_name);
> +		return ret;
> +	}
> +
> +	ret = ads1118_channel_set_pga(chan, fullscale);
> +	if (ret)
> +		dev_err(dev, "bad ti,fullscale on %s: invalid value\n",
> +			node->full_name);
> +
> +	return ret;
> +}
> +
> +static int ads1118_of_get_chan_datarate(struct ads1118 *ads,
> +					 struct device_node *node,
> +					 struct ads_channel *chan)
> +{
> +	int ret;
> +	u32 rate;
> +
> +	ret = of_property_read_u32(node, "ti,datarate", &rate);
> +	if (ret == -EINVAL) {
> +		rate = ads->ref->rates[ADS1118_DEFAULT_DR];
> +	} else if (ret) {
> +		dev_err(ads->dev, "bad ti,datarate on %s: should be u32\n",
> +			node->full_name);
> +		return ret;
> +	}
> +
> +	ret = ads1118_chan_set_rate(ads, chan, rate);
> +	if (ret)
> +		dev_err(ads->dev, "bad ti,datarate on %s: invalid value\n",
> +			node->full_name);
> +
> +	return ret;
> +}
> +
> +static int ads1118_of_get_chan_mux(struct device *dev,
> +				    struct device_node *node,
> +				    struct ads_channel *chan,
> +				    int chan_i)
> +{
> +	int ret;
> +	u32 de;
> +	u16 in2;
> +
> +	ret = of_property_read_u32(node, "ti,differential-endpoint", &de);
> +	if (ret == -EINVAL) {
> +		in2 = ADS1118_MUX_AINN_GND;
> +		goto set_mux;
> +	} else if (ret) {
> +		dev_err(dev, "bad ti,differential-endpoint on %s: should be a u32\n",
> +			node->full_name);
> +		return ret;
> +	}
> +
> +	switch (de) {
> +	case 1:
> +		in2 = ADS1118_MUX_AINN1;
> +		break;
> +	case 3:
> +		in2 = ADS1118_MUX_AINN3;
> +		break;
> +	default:
> +		dev_err(dev, "bad ti,differential-endpoint %d on %s\n",
> +			de, node->full_name);
> +		return -EINVAL;
> +	}
> +
> +set_mux:
> +	ret = ads1118_chan_set_mux(chan, (u16)chan_i, in2);
> +	if (ret)
> +		dev_err(dev, "bad ti,differential-endpoint pair %d, %d on %s\n",
> +			chan_i, de, node->full_name);
> +
> +	return ret;
> +}
> +
> +static void ads1118_of_cfg_chan(struct ads1118 *ads, struct device_node *node)
> +{
> +	int ret;
> +	int chan_i;
> +	struct ads_channel *chan;
> +
> +	chan_i = ads1118_of_get_chan(ads->dev, node);
> +	if (chan_i < 0)
> +		return;
> +
> +	chan = &ads->channel_data[chan_i];
> +	chan->cfg = ADS1118_ADC_CFG;
> +	ret = ads1118_of_get_chan_pga(ads->dev, node, chan);
> +	if (ret)
> +		return;
> +
> +	ret = ads1118_of_get_chan_datarate(ads, node, chan);
> +	if (ret)
> +		return;
> +
> +	ret = ads1118_of_get_chan_mux(ads->dev, node, chan, chan_i);
> +	if (ret)
> +		return;
> +
> +	chan->enabled = true;
> +}
> +
> +static void ads1118_of_get_pullup(struct ads1118 *ads)
> +{
> +	int i;
> +
> +	if (of_find_property(ads->dev->of_node, "ti,pullup-disable", NULL))
> +		for (i = 0; i < ADS1118_NUM_CHANS; ++i)
> +			ads->channel_data[i].cfg &= ~(BIT(ADS1118_PULL_UP));
> +}
> +#endif
> +
> +static void ads1118_temp_chan_enable(struct ads1118 *ads)
> +{
> +	struct ads_channel *chan = &ads->channel_data[ADS1118_TEMP_CHAN];
> +	unsigned int rate = ads->ref->rates[ADS1118_DEFAULT_DR];
> +
> +	chan->cfg = ADS1118_TEMP_CFG;
> +	ads1118_chan_set_rate(ads, chan, rate);
> +	chan->enabled = true;
> +}
> +
> +static int ads1118_get_cfg(struct ads1118 *ads)
> +{
> +	struct device_node *node;
> +
> +#ifndef CONFIG_OF
> +	return -EINVAL;
> +#else
> +	if (!ads->dev->of_node
> +	    || !of_get_next_child(ads->dev->of_node, NULL))
> +		return -EINVAL;
> +
> +	if (of_find_property(ads->dev->of_node, "ti,tempsensor", NULL))
> +		ads1118_temp_chan_enable(ads);
> +
> +	ads1118_of_get_pullup(ads);
> +
> +	for_each_child_of_node(ads->dev->of_node, node) {
> +		ads1118_of_cfg_chan(ads, node);
> +	}
> +
> +	return 0;
> +#endif
> +}
> +
> +static void ads1118_enable_all(struct ads1118 *ads)
> +{
> +	unsigned int i;
> +	unsigned int fullscale = fullscale_table[ADS1118_DEFAULT_PGA];
> +	unsigned int rate = ads->ref->rates[ADS1118_DEFAULT_DR];
> +
> +	ads1118_temp_chan_enable(ads);
> +
> +	for (i = 0; i < ADS1118_TEMP_CHAN; ++i) {
> +		struct ads_channel *chan = &ads->channel_data[i];
> +
> +		chan->cfg = ADS1118_ADC_CFG;
> +		ads1118_channel_set_pga(chan, fullscale);
> +		ads1118_chan_set_rate(ads, chan, rate);
> +		ads1118_chan_set_mux(chan, (u16)i, ADS1118_MUX_AINN_GND);
> +		chan->enabled = true;
> +	}
> +}
> +
> +static const struct of_device_id ads_1x18_ids[] = {
> +	{ .compatible = "ti,ads1018", .data = &ads1018_table, },
> +	{ .compatible = "ti,ads1118", .data = &ads1118_table, },
> +	{ /* sentinel */ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, ads_1x18_ids);
> +
> +static int ads1118_probe(struct spi_device *spi)
> +{
> +	const struct of_device_id *of_id;
> +	struct ads1118 *ads;
> +	int err;
> +
> +	ads = devm_kzalloc(&spi->dev, sizeof(struct ads1118),
> +			    GFP_KERNEL);
> +	if (!ads)
> +		return -ENOMEM;
> +
> +	of_id = of_match_device(ads_1x18_ids, &spi->dev);
> +	if (!of_id)
> +		return -EINVAL;
> +
> +	ads->ref = of_id->data;
> +	ads->dev = &spi->dev;
> +	mutex_init(&ads->update_lock);
> +	err = ads1118_get_cfg(ads);
> +	if (err)
> +		ads1118_enable_all(ads);
> +
> +	ads->hwmon_dev =
> +		devm_hwmon_device_register_with_groups(ads->dev, "ads11118",
> +						       ads, groups);
> +	if (IS_ERR(ads->hwmon_dev)) {
> +		err = PTR_ERR(ads->hwmon_dev);
> +		dev_err(ads->dev, "error initializing hwmon: %d\n", err);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct spi_driver ads1118_driver = {
> +	.driver = {
> +		.name = "ads1118",
> +		.of_match_table = ads_1x18_ids,
> +	},
> +	.probe = ads1118_probe,
> +};
> +
> +module_spi_driver(ads1118_driver);
> +
> +MODULE_AUTHOR("Joshua Clayton <stillcompiling@gmail.com>");
> +MODULE_DESCRIPTION("ADS1118 driver");
> +MODULE_LICENSE("GPL");
>

Re: [RCF 1/3] hwmon: Add ads1118 driver

[Joshua Clayton]

Greetings Guenter,

Thank you for reviewing my submission.

On 07/15/2016 06:40 PM, Guenter Roeck wrote:
> On 07/15/2016 05:18 PM, Joshua Clayton wrote:
>> Add new driver for Texas Instruments ADS1118 and and ADS1018.
>> This driver works with ADS1018, because of code borrowed
>> from asd1015, which is similar, but I can only test ADS1118
>>
>
> Browsing through the datasheet, I think this should probably be implemented
> as iio driver (and iio already has a driver for ads1015).
>
> Jonathan, what do you think ?
>
> Thanks,
> Guenter
>
No response from Jonathan as yet, but I am willing to rework the driver when I
have some time. It might be weeks before I can start, though.

I am not very familiar with the iio subsystem, (actually had never heard of it before
receiving your response). Learning it might be beneficial, as it looks like a good fit
for an in house driver, which I'd like to eventually upstream.

If an hwmon driver is adequate, I have new patches that address kbuild and endianness
issues in the first version.


~Joshua Clayton

ADS1118: hwmon or iio ? [was: Re: [RCF 1/3] hwmon: Add ads1118 driver]

[Guenter Roeck]

On 07/22/2016 07:39 AM, Joshua Clayton wrote:
> Greetings Guenter,
>
> Thank you for reviewing my submission.
>
> On 07/15/2016 06:40 PM, Guenter Roeck wrote:
>> On 07/15/2016 05:18 PM, Joshua Clayton wrote:
>>> Add new driver for Texas Instruments ADS1118 and and ADS1018.
>>> This driver works with ADS1018, because of code borrowed
>>> from asd1015, which is similar, but I can only test ADS1118
>>>
>>
>> Browsing through the datasheet, I think this should probably be implemented
>> as iio driver (and iio already has a driver for ads1015).
>>
>> Jonathan, what do you think ?
>>
>> Thanks,
>> Guenter
>>
> No response from Jonathan as yet, but I am willing to rework the driver when I
> have some time. It might be weeks before I can start, though.
>

Changing the subject - maybe it helps to get Jonathan's attention.

Guenter

Re: ADS1118: hwmon or iio ? [was: Re: [RCF 1/3] hwmon: Add ads1118 driver]

[Jonathan Cameron]

On 23/07/16 03:20, Guenter Roeck wrote:
> On 07/22/2016 07:39 AM, Joshua Clayton wrote:
>> Greetings Guenter,
>>
>> Thank you for reviewing my submission.
>>
>> On 07/15/2016 06:40 PM, Guenter Roeck wrote:
>>> On 07/15/2016 05:18 PM, Joshua Clayton wrote:
>>>> Add new driver for Texas Instruments ADS1118 and and ADS1018.
>>>> This driver works with ADS1018, because of code borrowed
>>>> from asd1015, which is similar, but I can only test ADS1118
>>>>
>>>
>>> Browsing through the datasheet, I think this should probably be implemented
>>> as iio driver (and iio already has a driver for ads1015).
>>>
>>> Jonathan, what do you think ?
>>>
>>> Thanks,
>>> Guenter
>>>
>> No response from Jonathan as yet, but I am willing to rework the driver when I
>> have some time. It might be weeks before I can start, though.
>>
> 
> Changing the subject - maybe it helps to get Jonathan's attention.
Sorry bit of silly travelling for day job over the last few days has
left me rather behind.

Just had my first experience of missing the last train home from the airport
and having to sleep in a 'pod' hotel waiting for the first on in the morning.

'interesting' and I hope I never have to repeat it.

Anyhow, looking fairly quickly through the datasheet I agree with Guenter.
This is a reasonably standard looking ADC with a decent analog front
end.  Whilst they state thermal monitoring in the 'applications' and there
are a few design choices in there (such as really small over voltage
protection) that make sense for thermocouples, there is nothing that
specific.  Also as Guenter has pointed out above we already have some
thermocouple focused chips in IIO.

Sampling is quick enough (up to 860 sps) that you'll probably want
to use the 'buffer' support in IIO rather than just a simple
polled (hwmon like) driver - but that can always come in a follow
up patch.  There is a nice datardy output that can be used to drive
a general purpose trigger (used to sample other devices in parallel
with this one if you want to).

Anyhow, all in, looks like a good general purpose ADC to me.
So would be delighted to have a driver for it in IIO.

You could combine it with the existing ads1015 driver, but
there are probably enough differences to make that fiddly
even using regmap to deal with the different bus (i2c -> spi),
so I think it doesn't really make sense (feel free to tell me
otherwise as I've only glanced at the datasheet!)

Thanks,

Jonathan

> 
> Guenter
> 
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Re: [RCF 1/3] hwmon: Add ads1118 driver

[Jonathan Cameron]

On 22/07/16 16:39, Joshua Clayton wrote:
> Greetings Guenter,
> 
> Thank you for reviewing my submission.
> 
> On 07/15/2016 06:40 PM, Guenter Roeck wrote:
>> On 07/15/2016 05:18 PM, Joshua Clayton wrote:
>>> Add new driver for Texas Instruments ADS1118 and and ADS1018.
>>> This driver works with ADS1018, because of code borrowed
>>> from asd1015, which is similar, but I can only test ADS1118
>>>
>>
>> Browsing through the datasheet, I think this should probably be implemented
>> as iio driver (and iio already has a driver for ads1015).
>>
>> Jonathan, what do you think ?
>>
>> Thanks,
>> Guenter
>>
> No response from Jonathan as yet, but I am willing to rework the driver when I
> have some time. It might be weeks before I can start, though.
Sorry, made week and I thought I'd have time to get reviews done in evenings
so didn't look at anything last weekend.   Catching up on train home this morning.
> 
> I am not very familiar with the iio subsystem, (actually had never heard of it before
> receiving your response). Learning it might be beneficial, as it looks like a good fit
> for an in house driver, which I'd like to eventually upstream.
Cool
> 
> If an hwmon driver is adequate, I have new patches that address kbuild and endianness
> issues in the first version.
I'd flip it over to IIO.  If you keep to just the simple bits it'll end up pretty
simple to do.
> 
> 
> ~Joshua Clayton
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