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Date: Thu, 29 Jun 2017 13:30:46 +0200
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Frans Klaver <fransklaver@...il.com>
CC: <linux-hwmon@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Guenter Roeck <linux@...ck-us.net>, <jdelvare@...e.com>
Subject: Re: [PATCH] hwmon: Add LTC2471/LTC2473 driver
On 29-06-17 13:18, Frans Klaver wrote:
> On Thu, Jun 29, 2017 at 12:45 PM, Mike Looijmans
> <mike.looijmans@...ic.nl> wrote:
>> The LTC2741 and LTC2473 are single voltage monitoring chips. The LTC2473
>> is similar to the LTC2471 but outputs a signed differential value.
>>
>> Datasheet:
>> http://cds.linear.com/docs/en/datasheet/24713fb.pdf
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>> ---
>> drivers/hwmon/Kconfig | 10 ++++
>> drivers/hwmon/Makefile | 1 +
>> drivers/hwmon/ltc2471.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 138 insertions(+)
>> create mode 100644 drivers/hwmon/ltc2471.c
>>
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index fbde226..c9a2a87 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -673,6 +673,16 @@ config SENSORS_LINEAGE
>> This driver can also be built as a module. If so, the module
>> will be called lineage-pem.
>>
>> +config SENSORS_LTC2471
>> + tristate "Linear Technology LTC2471 and LTC2473"
>> + depends on I2C
>> + help
>> + If you say yes here you get support for Linear Technology LTC2471
>> + and LTC2473 voltage monitors.
>> +
>> + This driver can also be built as a module. If so, the module will
>> + be called ltc2471.
>> +
>> config SENSORS_LTC2945
>> tristate "Linear Technology LTC2945"
>> depends on I2C
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index 58cc3ac..6f60fe7 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -99,6 +99,7 @@ obj-$(CONFIG_SENSORS_LM93) += lm93.o
>> obj-$(CONFIG_SENSORS_LM95234) += lm95234.o
>> obj-$(CONFIG_SENSORS_LM95241) += lm95241.o
>> obj-$(CONFIG_SENSORS_LM95245) += lm95245.o
>> +obj-$(CONFIG_SENSORS_LTC2471) += ltc2471.o
>> obj-$(CONFIG_SENSORS_LTC2945) += ltc2945.o
>> obj-$(CONFIG_SENSORS_LTC2990) += ltc2990.o
>> obj-$(CONFIG_SENSORS_LTC4151) += ltc4151.o
>> diff --git a/drivers/hwmon/ltc2471.c b/drivers/hwmon/ltc2471.c
>> new file mode 100644
>> index 0000000..17eaad8
>> --- /dev/null
>> +++ b/drivers/hwmon/ltc2471.c
>> @@ -0,0 +1,127 @@
>> +/*
>> + * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
>> + * The LTC2473 is identical to the 2471, but reports a differential signal.
>> + *
>> + * Copyright (C) 2017 Topic Embedded Products
>> + * Author: Mike Looijmans <mike.looijmans@...ic.nl>
>> + *
>> + * License: GPLv2
>> + */
>> +
>> +#include <linux/err.h>
>> +#include <linux/hwmon.h>
>> +#include <linux/hwmon-sysfs.h>
>> +#include <linux/i2c.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +
>> +enum chips {
>> + ltc2471,
>> + ltc2473
>> +};
>> +
>> +struct ltc2471_data {
>> + struct i2c_client *i2c;
>> + bool differential;
>> +};
>
> I haven't checked if there are similar drivers, but how about
> ltc247x_data? It's a bit odd to tie all naming in this driver to one
> chip and then support another one as well.
Did a query on the linear site, found the LTC2470 and LTC2472 which appear to
be the SPI versions of the same chip. So yes, using "ltc247x" may cause
confusion when other drivers arrive. Linear solves this by naming the
datasheet "ltc24712" but I think that'd be even more confusing.
>
>> +
>> +/* Reference voltage is 1.25V */
>> +#define LTC2471_VREF 1250
>> +
>> +/* Read two bytes from the I2C bus to obtain the ADC result */
>> +static int ltc2471_get_value(struct i2c_client *i2c)
>> +{
>> + int ret;
>> + __be16 buf;
>> +
>> + ret = i2c_master_recv(i2c, (char *)&buf, 2);
>> + if (ret < 0)
>> + return ret;
>> + if (ret != 2)
>> + return -EIO;
>> +
>> + /* MSB first */
>> + return be16_to_cpu(buf);
>> +}
>> +
>> +static ssize_t ltc2471_show_value(struct device *dev,
>> + struct device_attribute *da, char *buf)
>> +{
>> + struct ltc2471_data *data = dev_get_drvdata(dev);
>> + int value;
>> +
>> + value = ltc2471_get_value(data->i2c);
>> + if (unlikely(value < 0))
>> + return value;
>> +
>> + if (data->differential)
>> + /* Ranges from -VREF to +VREF with "0" at 0x8000 */
>> + value = ((s32)LTC2471_VREF * (s32)(value - 0x8000)) >> 15;
>> + else
>> + /* Ranges from 0 to +VREF */
>> + value = ((u32)LTC2471_VREF * (u32)value) >> 16;
>> +
>> + return snprintf(buf, PAGE_SIZE, "%d\n", value);
>> +}
>> +
>> +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ltc2471_show_value, NULL, 0);
>
> Octal permissions are preferred over S_IRUGO and such.
Uh, can elaborate on that, or give an example on what you mean by that remark?
A quick grep reveils that most (if not all) hwmon devices are currently using
"S_IRUGO" and such.
>> +
>> +static struct attribute *ltc2471_attrs[] = {
>> + &sensor_dev_attr_in0_input.dev_attr.attr,
>> + NULL
>> +};
>> +
>> +ATTRIBUTE_GROUPS(ltc2471);
>> +
>> +static int ltc2471_i2c_probe(struct i2c_client *i2c,
>> + const struct i2c_device_id *id)
>> +{
>> + int ret;
>> + struct device *hwmon_dev;
>> + struct ltc2471_data *data;
>> +
>> + if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_I2C))
>> + return -ENODEV;
>> +
>> + data = devm_kzalloc(&i2c->dev, sizeof(struct ltc2471_data), GFP_KERNEL);
>
> sizeof(*data)
OK.
>
>> + if (unlikely(!data))
>> + return -ENOMEM;
>> +
>> + data->i2c = i2c;
>> + data->differential = (id->driver_data == ltc2473);
>> +
>> + /* Trigger once to start conversion and check if chip is there */
>> + ret = ltc2471_get_value(i2c);
>> + if (ret < 0) {
>> + dev_err(&i2c->dev, "Cannot read from device.\n");
>> + return ret;
>> + }
>> +
>> + hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
>> + i2c->name,
>> + data,
>> + ltc2471_groups);
>> +
>> + return PTR_ERR_OR_ZERO(hwmon_dev);
>> +}
>> +
>> +static const struct i2c_device_id ltc2471_i2c_id[] = {
>> + { "ltc2471", ltc2471 },
>> + { "ltc2473", ltc2473 },
>> + {}
>> +};
>> +MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
>> +
>> +static struct i2c_driver ltc2471_i2c_driver = {
>> + .driver = {
>> + .name = "ltc2471",
>> + },
>> + .probe = ltc2471_i2c_probe,
>> + .id_table = ltc2471_i2c_id,
>> +};
>> +
>> +module_i2c_driver(ltc2471_i2c_driver);
>> +
>> +MODULE_DESCRIPTION("LTC2471/LTC2473 Sensor Driver");
>> +MODULE_AUTHOR("Topic Embedded Products");
>> +MODULE_LICENSE("GPL v2");
>> --
>> 1.9.1
>>
>
> Frans
>
Kind regards,
Mike Looijmans
System Expert
TOPIC Products
Materiaalweg 4, NL-5681 RJ Best
Postbus 440, NL-5680 AK Best
Telefoon: +31 (0) 499 33 69 79
E-mail: mike.looijmans@...icproducts.com
Website: www.topicproducts.com
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