Re: [PATCH 1/2 v2] hwmon: (ltc4151) Make shunt-resistor configurable

[Daniel Golle <daniel-g5gK2j5usbvCyp4qypjU+w@public.gmane.org>]

Hi Guenter,

On Sat, Jul 30, 2016 at 09:00:14AM -0700, Guenter Roeck wrote:
> Daniel,
> 
> On 07/25/2016 04:56 AM, Daniel Golle wrote:
> > Allow to specify the resistance of the attached shunt via DT by
> > adding the shunt-resistor property. Fall-back to the previous
> > default (1 mOhm) if unset.
> > 
> > Signed-off-by: Daniel Golle <daniel-g5gK2j5usbvCyp4qypjU+w@public.gmane.org>
> 
> Please resend with the property name changed as asked for by Rob.

Ok, will do. I originally copy-pasted the property name from ina209,
so I reckon it's supposed to be changed there as well...?

Cheers

Daniel

> 
> Thanks,
> Guenter
> 
> > ---
> > v2: removed unneeded things and throw -EINVAL for shunt==0
> > 
> >   drivers/hwmon/ltc4151.c | 21 +++++++++++++++++++--
> >   1 file changed, 19 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/hwmon/ltc4151.c b/drivers/hwmon/ltc4151.c
> > index c86a184..419c6f7 100644
> > --- a/drivers/hwmon/ltc4151.c
> > +++ b/drivers/hwmon/ltc4151.c
> > @@ -30,6 +30,7 @@
> > 
> >   #include <linux/kernel.h>
> >   #include <linux/module.h>
> > +#include <linux/of.h>
> >   #include <linux/init.h>
> >   #include <linux/err.h>
> >   #include <linux/slab.h>
> > @@ -52,6 +53,7 @@ struct ltc4151_data {
> >   	struct mutex update_lock;
> >   	bool valid;
> >   	unsigned long last_updated; /* in jiffies */
> > +	unsigned int shunt; /* in micro ohms */
> > 
> >   	/* Registers */
> >   	u8 regs[6];
> > @@ -111,9 +113,9 @@ static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
> >   	case LTC4151_SENSE_H:
> >   		/*
> >   		 * 20uV resolution. Convert to current as measured with
> > -		 * an 1 mOhm sense resistor, in mA.
> > +		 * a given sense resistor, in mA.
> >   		 */
> > -		val = val * 20;
> > +		val = val * 20 * 1000 / data->shunt;
> >   		break;
> >   	case LTC4151_VIN_H:
> >   		/* 25 mV per increment */
> > @@ -176,6 +178,7 @@ static int ltc4151_probe(struct i2c_client *client,
> >   	struct device *dev = &client->dev;
> >   	struct ltc4151_data *data;
> >   	struct device *hwmon_dev;
> > +	u32 shunt;
> > 
> >   	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
> >   		return -ENODEV;
> > @@ -184,6 +187,14 @@ static int ltc4151_probe(struct i2c_client *client,
> >   	if (!data)
> >   		return -ENOMEM;
> > 
> > +	if (of_property_read_u32(client->dev.of_node, "shunt-resistor", &shunt))
> > +		shunt = 1000; /* 1 mOhm if not set via DT */
> > +
> > +	if (shunt == 0)
> > +		return -EINVAL;
> > +
> > +	data->shunt = shunt;
> > +
> >   	data->client = client;
> >   	mutex_init(&data->update_lock);
> > 
> > @@ -199,10 +210,16 @@ static const struct i2c_device_id ltc4151_id[] = {
> >   };
> >   MODULE_DEVICE_TABLE(i2c, ltc4151_id);
> > 
> > +static const struct of_device_id ltc4151_match[] = {
> > +	{ .compatible = "lltc,ltc4151" },
> > +	{},
> > +};
> > +
> >   /* This is the driver that will be inserted */
> >   static struct i2c_driver ltc4151_driver = {
> >   	.driver = {
> >   		.name	= "ltc4151",
> > +		.of_match_table = of_match_ptr(ltc4151_match),
> >   	},
> >   	.probe		= ltc4151_probe,
> >   	.id_table	= ltc4151_id,
> > 
> 
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