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+======================
+Kernel driver w1_therm
+======================
+
+Supported chips:
+
+ * Maxim ds18*20 based temperature sensors.
+ * Maxim ds1825 based temperature sensors.
+ * GXCAS GC20MH01 temperature sensor.
+
+Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
+
+
+Description
+-----------
+
+w1_therm provides basic temperature conversion for ds18*20, ds28ea00, GX20MH01
+devices.
+
+Supported family codes:
+
+==================== ====
+W1_THERM_DS18S20 0x10
+W1_THERM_DS1822 0x22
+W1_THERM_DS18B20 0x28
+W1_THERM_DS1825 0x3B
+W1_THERM_DS28EA00 0x42
+==================== ====
+
+Support is provided through the sysfs entry ``w1_slave``. Each open and
+read sequence will initiate a temperature conversion, then provide two
+lines of ASCII output. The first line contains the nine hex bytes
+read along with a calculated crc value and YES or NO if it matched.
+If the crc matched the returned values are retained. The second line
+displays the retained values along with a temperature in millidegrees
+Centigrade after t=.
+
+Alternatively, temperature can be read using ``temperature`` sysfs, it
+returns only the temperature in millidegrees Centigrade.
+
+A bulk read of all devices on the bus could be done writing ``trigger``
+to ``therm_bulk_read`` entry at w1_bus_master level. This will
+send the convert command to all devices on the bus, and if parasite
+powered devices are detected on the bus (and strong pullup is enabled
+in the module), it will drive the line high during the longer conversion
+time required by parasited powered device on the line. Reading
+``therm_bulk_read`` will return 0 if no bulk conversion pending,
+-1 if at least one sensor still in conversion, 1 if conversion is complete
+but at least one sensor value has not been read yet. Result temperature is
+then accessed by reading the ``temperature`` entry of each device, which
+may return empty if conversion is still in progress. Note that if a bulk
+read is sent but one sensor is not read immediately, the next access to
+``temperature`` on this device will return the temperature measured at the
+time of issue of the bulk read command (not the current temperature).
+
+A strong pullup will be applied during the conversion if required.
+
+``conv_time`` is used to get current conversion time (read), and
+adjust it (write). A temperature conversion time depends on the device type and
+it's current resolution. Default conversion time is set by the driver according
+to the device datasheet. A conversion time for many original device clones
+deviate from datasheet specs. There are three options: 1) manually set the
+correct conversion time by writing a value in milliseconds to ``conv_time``; 2)
+auto measure and set a conversion time by writing ``1`` to
+``conv_time``; 3) use ``features`` to enable poll for conversion
+completion. Options 2, 3 can't be used in parasite power mode. To get back to
+the default conversion time write ``0`` to ``conv_time``.
+
+Writing a resolution value (in bits) to ``w1_slave`` will change the
+precision of the sensor for the next readings. Allowed resolutions are defined by
+the sensor. Resolution is reset when the sensor gets power-cycled.
+
+To store the current resolution in EEPROM, write ``0`` to ``w1_slave``.
+Since the EEPROM has a limited amount of writes (>50k), this command should be
+used wisely.
+
+Alternatively, resolution can be read or written using the dedicated
+``resolution`` entry on each device, if supported by the sensor.
+
+Some non-genuine DS18B20 chips are fixed in 12-bit mode only, so the actual
+resolution is read back from the chip and verified.
+
+Note: Changing the resolution reverts the conversion time to default.
+
+The write-only sysfs entry ``eeprom`` is an alternative for EEPROM operations.
+Write ``save`` to save device RAM to EEPROM. Write ``restore`` to restore EEPROM
+data in device RAM.
+
+``ext_power`` entry allows checking the power state of each device. Reads
+``0`` if the device is parasite powered, ``1`` if the device is externally powered.
+
+Sysfs ``alarms`` allow read or write TH and TL (Temperature High an Low) alarms.
+Values shall be space separated and in the device range (typical -55 degC
+to 125 degC). Values are integer as they are store in a 8bit register in
+the device. Lowest value is automatically put to TL. Once set, alarms could
+be search at master level.
+
+The module parameter strong_pullup can be set to 0 to disable the
+strong pullup, 1 to enable autodetection or 2 to force strong pullup.
+In case of autodetection, the driver will use the "READ POWER SUPPLY"
+command to check if there are pariste powered devices on the bus.
+If so, it will activate the master's strong pullup.
+In case the detection of parasite devices using this command fails
+(seems to be the case with some DS18S20) the strong pullup can
+be force-enabled.
+
+If the strong pullup is enabled, the master's strong pullup will be
+driven when the conversion is taking place, provided the master driver
+does support the strong pullup (or it falls back to a pullup
+resistor). The DS18b20 temperature sensor specification lists a
+maximum current draw of 1.5mA and that a 5k pullup resistor is not
+sufficient. The strong pullup is designed to provide the additional
+current required.
+
+The DS28EA00 provides an additional two pins for implementing a sequence
+detection algorithm. This feature allows you to determine the physical
+location of the chip in the 1-wire bus without needing pre-existing
+knowledge of the bus ordering. Support is provided through the sysfs
+``w1_seq``. The file will contain a single line with an integer value
+representing the device index in the bus starting at 0.
+
+``features`` sysfs entry controls optional driver settings per device.
+Insufficient power in parasite mode, line noise and insufficient conversion
+time may lead to conversion failure. Original DS18B20 and some clones allow for
+detection of invalid conversion. Write bit mask ``1`` to ``features`` to enable
+checking the conversion success. If byte 6 of scratchpad memory is 0xC after
+conversion and temperature reads 85.00 (powerup value) or 127.94 (insufficient
+power), the driver returns a conversion error. Bit mask ``2`` enables poll for
+conversion completion (normal power only) by generating read cycles on the bus
+after conversion starts. In parasite power mode this feature is not available.
+Feature bit masks may be combined (OR). More details in
+Documentation/ABI/testing/sysfs-driver-w1_therm
+
+GX20MH01 device shares family number 0x28 with DS18*20. The device is generally
+compatible with DS18B20. Added are lowest 2\ :sup:`-5`, 2\ :sup:`-6` temperature
+bits in Config register; R2 bit in Config register enabling 13 and 14 bit
+resolutions. The device is powered up in 14-bit resolution mode. The conversion
+times specified in the datasheet are too low and have to be increased. The
+device supports driver features ``1`` and ``2``.