On Mon, Dec 24, 2012 at 11:49:06AM -0800, Chris Verges wrote: > The LM73 supports four A/D conversion resolutions. The default used by > the existing lm73 driver is the chip's default, 11-bit (0.25 C/LSB). > This patch enables changing of this resolution from userspace via the > temp1_update_interval attribute. Full details on use of this mechanism > are described in Documentation/hwmon/lm73. > > Signed-off-by: Chris Verges <kg4ysn@xxxxxxxxx> I'll be out of town for the next couple of weeks. I'll get back to you afterwards. Guenter > --- > Documentation/hwmon/lm73 | 78 ++++++++++++++++++++++++++++++++++++++++++++++ > drivers/hwmon/lm73.c | 76 +++++++++++++++++++++++++++++++++++++++++--- > 2 files changed, 150 insertions(+), 4 deletions(-) > create mode 100644 Documentation/hwmon/lm73 > > diff --git a/Documentation/hwmon/lm73 b/Documentation/hwmon/lm73 > new file mode 100644 > index 0000000..2d947d3 > --- /dev/null > +++ b/Documentation/hwmon/lm73 > @@ -0,0 +1,78 @@ > +Kernel driver lm90 > +================== > + > +Supported chips: > + * Texas Instruments LM73 > + Prefix: 'lm73' > + Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e > + Datasheet: Publicly available at the Texas Instruments website > + http://www.ti.com/product/lm73 > + > +Author: Chris Verges <kg4ysn@xxxxxxxxx> > + > + > +Description > +----------- > + > +The LM73 is a digital temperature sensor. All temperature values are > +given in degrees Celsius. > + > +Measurement Resolution Support > +------------------------------ > + > +The LM73 supports four resolutions, defined in terms of degrees C per > +LSB: 0.25, 0.125, 0.0625, and 0.3125. Changing the resolution mode > +affects the conversion time of the LM73's analog-to-digital converter. > +From userspace, the desired resolution can be specified as a function of > +conversion time via the 'update_interval' sysfs attribute for the > +device. This attribute will normalize ranges of input values to the > +maximum times defined for the resolution in the datasheet. > + > + Resolution Conv. Time Input Range > + (C/LSB) (msec) (msec) > + -------------------------------------- > + 0.25 14 0..21 > + 0.125 28 22..42 > + 0.0625 56 43..84 > + 0.03125 112 85..infinity > + -------------------------------------- > + > +The following examples show how the 'update_interval' attribute can be > +used to change the conversion time: > + > + $ echo 0 > temp1_update_interval > + $ cat temp1_update_interval > + 14 > + $ cat temp1_input > + 24250 > + > + $ echo 36 > temp1_update_interval > + $ cat temp1_update_interval > + 28 > + $ cat temp1_input > + 24125 > + > + $ echo 56 > temp1_update_interval > + $ cat temp1_update_interval > + 56 > + $ cat temp1_input > + 24062 > + > + $ echo 85 > temp1_update_interval > + $ cat temp1_update_interval > + 112 > + $ cat temp1_input > + 24031 > + > +As shown here, the lm73 driver automatically adjusts any user input for > +'update_interval' via a step function. Reading back the > +'update_interval' value after a write operation will confirm the > +conversion time actively in use. > + > +Mathematically, the resolution can be derived from the conversion time > +via the following function: > + > + g(x) = 0.250 * [log(x/14) / log(2)] > + > +where 'x' is the output from 'update_interval' and 'g(x)' is the > +resolution in degrees C per LSB. > diff --git a/drivers/hwmon/lm73.c b/drivers/hwmon/lm73.c > index 7272176..f443fad 100644 > --- a/drivers/hwmon/lm73.c > +++ b/drivers/hwmon/lm73.c > @@ -21,7 +21,6 @@ > #include <linux/hwmon-sysfs.h> > #include <linux/err.h> > > - > /* Addresses scanned */ > static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c, > 0x4d, 0x4e, I2C_CLIENT_END }; > @@ -39,8 +38,20 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c, > #define LM73_TEMP_MIN (-40) > #define LM73_TEMP_MAX 150 > > -/*-----------------------------------------------------------------------*/ > +#define LM73_CTRL_RES_SHIFT 5 > +#define LM73_CTRL_RES_SIZE 2 > +#define LM73_CTRL_RES_MASK ((1 << LM73_CTRL_RES_SIZE) - 1) > > +#define SCALE_150_PERCENT(x) (((x) * 150) / 100) > + > +static const unsigned short lm73_valid_convrates[] = { > + 14, /* 11-bits (0.25000 C/LSB): RES1 Bit = 0, RES0 Bit = 0 */ > + 28, /* 12-bits (0.12500 C/LSB): RES1 Bit = 0, RES0 Bit = 1 */ > + 56, /* 13-bits (0.06250 C/LSB): RES1 Bit = 1, RES0 Bit = 0 */ > + 112, /* 14-bits (0.03125 C/LSB): RES1 Bit = 1, RES0 Bit = 1 */ > +}; > + > +/*-----------------------------------------------------------------------*/ > > static ssize_t set_temp(struct device *dev, struct device_attribute *da, > const char *buf, size_t count) > @@ -79,6 +90,62 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *da, > return scnprintf(buf, PAGE_SIZE, "%d\n", temp); > } > > +static ssize_t set_convrate(struct device *dev, struct device_attribute *da, > + const char *buf, size_t count) > +{ > + struct i2c_client *client = to_i2c_client(dev); > + unsigned long convrate; > + s32 err; > + u8 res_bits = 0; > + u8 value; > + > + err = kstrtoul(buf, 10, &convrate); > + if (err < 0) > + return err; > + > + /* Read existing control value */ > + err = i2c_smbus_read_byte_data(client, LM73_REG_CTRL); > + if (err < 0) > + return err; > + value = err; > + > + /* Convert the desired conversion rate into register bits */ > + if (convrate < SCALE_150_PERCENT(lm73_valid_convrates[0])) > + res_bits = 0; > + else if (convrate < SCALE_150_PERCENT(lm73_valid_convrates[1])) > + res_bits = 1; > + else if (convrate < SCALE_150_PERCENT(lm73_valid_convrates[2])) > + res_bits = 2; > + else > + res_bits = 3; > + > + /* Create the new control register value */ > + value &= ~(LM73_CTRL_RES_MASK << LM73_CTRL_RES_SHIFT); > + value |= (res_bits << LM73_CTRL_RES_SHIFT); > + > + /* Write value */ > + err = i2c_smbus_write_byte_data(client, LM73_REG_CTRL, value); > + if (err < 0) > + return err; > + return count; > +} > + > +static ssize_t show_convrate(struct device *dev, struct device_attribute *da, > + char *buf) > +{ > + struct i2c_client *client = to_i2c_client(dev); > + uint32_t ctrl; > + u8 res_bits = 0; > + > + /* Read existing control value */ > + ctrl = i2c_smbus_read_byte_data(client, LM73_REG_CTRL); > + if (ctrl < 0) > + return ctrl; > + > + res_bits = (ctrl >> LM73_CTRL_RES_SHIFT) & LM73_CTRL_RES_MASK; > + return scnprintf(buf, PAGE_SIZE, "%hu\n", > + lm73_valid_convrates[res_bits]); > +} > > /*-----------------------------------------------------------------------*/ > > @@ -90,13 +157,14 @@ static SENSOR_DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO, > show_temp, set_temp, LM73_REG_MIN); > static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, > show_temp, NULL, LM73_REG_INPUT); > - > +static SENSOR_DEVICE_ATTR(temp1_update_interval, S_IWUSR | S_IRUGO, > + show_convrate, set_convrate, LM73_REG_CTRL); > > static struct attribute *lm73_attributes[] = { > &sensor_dev_attr_temp1_input.dev_attr.attr, > &sensor_dev_attr_temp1_max.dev_attr.attr, > &sensor_dev_attr_temp1_min.dev_attr.attr, > - > + &sensor_dev_attr_temp1_update_interval.dev_attr.attr, > NULL > }; > > -- > 1.7.9.5 > > _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
