[PATCH v2 2/2] w1_therm documentation

[Akira SHIMAHARA]

* updating w1_therm.rst documentation

* adding sysfs-driver-w1_therm documentation

Signed-off-by: Akira Shimahara <akira215corp@xxxxxxxxx>
---
Changes in v2:
 - Adding documentation in Documentatin/ABI/testing/sysfs-driver-
w1_therm
 - Updating existing documentation in
Documentation/w1/slaves/w1_therm.rst

 .../ABI/testing/sysfs-driver-w1_therm         | 115 ++++++++++++++++++
 Documentation/w1/slaves/w1_therm.rst          |  52 ++++++--
 2 files changed, 157 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-w1_therm

diff --git a/Documentation/ABI/testing/sysfs-driver-w1_therm
b/Documentation/ABI/testing/sysfs-driver-w1_therm
new file mode 100644
index 0000000000000..e18261189684c
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-w1_therm
@@ -0,0 +1,115 @@
+What:		/sys/bus/w1/devices/.../alarms
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(RW) 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, refer
to
+		Documentation/w1/w1_generic.rst for detailed
information
+Users:		any user space application which wants to communicate
with
+		w1_term device
+
+
+What:		/sys/bus/w1/devices/.../eeprom
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(WO) writing that file will either trigger a save of
the
+		device data to its embedded EEPROM, either restore data
+		embedded in device EEPROM. Be aware that devices
support
+		limited EEPROM writing cycles (typical 50k)
+			* `save`: save device RAM to EEPROM
+			* `restore`: restore EEPROM data in device RAM
+Users:		any user space application which wants to communicate
with
+		w1_term device
+
+
+What:		/sys/bus/w1/devices/.../ext_power
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(RO) return the power status by asking the device
+			* `0`: device parasite powered
+			* `1`: device externally powered
+			* `-xx`: xx is kernel error when reading power
status
+Users:		any user space application which wants to communicate
with
+		w1_term device
+
+
+What:		/sys/bus/w1/devices/.../resolution
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(RW) get or set the device resolution (on supported
devices,
+		if not, this entry is not present). Note that the
resolution
+		will be changed only in device RAM, so it will be
cleared when
+		power is lost. Trigger a `save` to EEPROM command to
keep
+		values after power-on. Read or write are :
+			* `9..12`: device resolution in bit
+			or resolution to set in bit
+			* `-xx`: xx is kernel error when reading the
resolution
+			* Anything else: do nothing
+Users:		any user space application which wants to communicate
with
+		w1_term device
+
+
+What:		/sys/bus/w1/devices/.../temperature
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(RO) return the temperature in 1/1000 degC.
+			* If a bulk read has been triggered, it will
directly
+			return the temperature computed when the bulk
read
+			occurred, if available. If not yet available,
nothing
+			is returned (a debug kernel message is sent),
you
+			should retry later on.
+			* If no bulk read has been triggered, it will
trigger
+			a conversion and send the result. Note that the
+			conversion duration depend on the resolution
(if
+			device support this feature). It takes 94ms in
9bits
+			resolution, 750ms for 12bits.
+Users:		any user space application which wants to communicate
with
+		w1_term device
+
+
+What:		/sys/bus/w1/devices/.../w1_slave
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(RW) return the temperature in 1/1000 degC.
+		*read*: return 2 lines with the hexa output data sent
on the
+		bus, return the CRC check and temperature in 1/1000
degC
+		*write* :
+			* `0` : save the 2 or 3 bytes to the device
EEPROM
+			(i.e. TH, TL and config register)
+			* `9..12` : set the device resolution in RAM
+			(if supported)
+			* Anything else: do nothing
+		refer to Documentation/w1/slaves/w1_therm.rst for
detailed
+		information.
+Users:		any user space application which wants to communicate
with
+		w1_term device
+
+
+What:		/sys/bus/w1/devices/w1_bus_masterXX/therm_bulk_read
+Date:		Apr 2020
+Contact:	Akira Shimahara <akira215corp@xxxxxxxxx>
+Description:
+		(RW) return the temperature in 1/1000 degC.
+		*read*:
+			* `-1`: conversion in progress on at least 1
sensor
+			* `1` :	conversion complete but at least one
sensor
+				value has not been read yet
+			* `0` :	no bulk operation. Reading temperature
will
+				trigger a conversion on each device
+		*write*: `trigger`: trigger a bulk read on all
supporting
+			devices on the bus
+		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).
+Users:		any user space application which wants to communicate
with
+		w1_term device
diff --git a/Documentation/w1/slaves/w1_therm.rst
b/Documentation/w1/slaves/w1_therm.rst
index 90531c340a07a..06eaff1a05c08 100644
--- a/Documentation/w1/slaves/w1_therm.rst
+++ b/Documentation/w1/slaves/w1_therm.rst
@@ -26,20 +26,31 @@ W1_THERM_DS1825		0x3B
 W1_THERM_DS28EA00	0x42
 ====================	====
 
-Support is provided through the sysfs w1_slave file.  Each open and
+Support is provided through the sysfs w1_slave file. 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
+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
+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=.
 
-Parasite powered devices are limited to one slave performing a
-temperature conversion at a time.  If none of the devices are parasite
-powered it would be possible to convert all the devices at the same
-time and then go back to read individual sensors.  That isn't
-currently supported.  The driver also doesn't support reduced
-precision (which would also reduce the conversion time) when reading
values.
+Alternatively, temperature can be read using temperature sysfs, it
+return only temperature in millidegrees Centigrade.
+
+A bulk read of all devices on the bus could be done writing 'trigger'
+in the therm_bulk_read sysfs entry at w1_bus_master level. This will
+sent the convert command on all devices on the bus, and if parasite
+powered devices are detected on the bus (and strong pullup is enable
+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 sysfs 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).
 
 Writing a value between 9 and 12 to the sysfs w1_slave file will
change the
 precision of the sensor for the next readings. This value is in
(volatile)
@@ -49,6 +60,27 @@ To store the current precision configuration into
EEPROM, the value 0
 has to be written to the sysfs w1_slave file. Since the EEPROM has a
limited
 amount of writes (>50k), this command should be used wisely.
 
+Alternatively, resolution can be set or read (value from 9 to 12)
using the
+dedicated resolution sysfs entry on each device. This sysfs entry is
not
+present for devices not supporting this feature. Driver will adjust
the
+correct conversion time for each device regarding to its resolution
setting.
+In particular, strong pullup will be applied if required during the
conversion
+duration.
+
+The write-only sysfs entry eeprom is an alternative for EEPROM
operations:
+  * `save`: will save device RAM to EEPROM
+  * `restore`: will restore EEPROM data in device RAM.
+
+ext_power syfs entry allow tho check the power status of each device.
+  * `0`: device parasite powered
+  * `1`: device 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"
@@ -71,4 +103,4 @@ 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 file.  The file will contain a single line with an integer
value
-representing the device index in the bus starting at 0.
+representing the device index in the bus starting at 0.
\ No newline at end of file