Merge tag 'gpio-for-linus' of git://git.secretlab.ca/git/linux

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / hwmon / lm95234

Kernel driver lm95234
=====================

Supported chips:
  * National Semiconductor / Texas Instruments LM95234
    Addresses scanned: I2C 0x18, 0x4d, 0x4e
    Datasheet: Publicly available at the Texas Instruments website
               http://www.ti.com/product/lm95234


Author: Guenter Roeck <linux@roeck-us.net>

Description
-----------

LM95234 is an 11-bit digital temperature sensor with a 2-wire System Management
Bus (SMBus) interface and TrueTherm technology that can very accurately monitor
the temperature of four remote diodes as well as its own temperature.
The four remote diodes can be external devices such as microprocessors,
graphics processors or diode-connected 2N3904s. The LM95234's TruTherm
beta compensation technology allows sensing of 90 nm or 65 nm process
thermal diodes accurately.

All temperature values are given in millidegrees Celsius. Temperature
is provided within a range of -127 to +255 degrees (+127.875 degrees for
the internal sensor). Resolution depends on temperature input and range.

Each sensor has its own maximum limit, but the hysteresis is common to all
channels. The hysteresis is configurable with the tem1_max_hyst attribute and
affects the hysteresis on all channels. The first two external sensors also
have a critical limit.

The lm95234 driver can change its update interval to a fixed set of values.
It will round up to the next selectable interval. See the datasheet for exact
values. Reading sensor values more often will do no harm, but will return
'old' values.