57c76221d5
Adding bulk read support:
Sending a 'trigger' command in the dedicated sysfs entry of bus master
device send a conversion command for all the slaves on the bus. The sysfs
entry is added as soon as at least one device supporting this feature
is detected on the bus.
The behavior of the sysfs reading temperature on the device is as follow:
* If no bulk read pending, trigger a conversion on the device, wait for
the conversion to be done, read the temperature in device RAM
* If a bulk read has been trigger, access directly the device RAM
This behavior is the same on the 2 sysfs entries ('temperature' and
'w1_slave').
Reading the therm_bulk_read sysfs give the status of bulk operations:
* '-1': conversion in progress on at least 1 sensor
* '1': conversion complete but at least one sensor has not been read yet
* '0': no bulk operation. Reading temperature on ecah device will trigger
a conversion
As not all devices support bulk read feature, it has been added in device
family structure.
The attribute is set at master level as soon as a supporting device is
discover. It is removed when the last supported device leave the bus.
The count of supported device is kept with the static counter
bulk_read_device_counter.
A strong pull up is apply on the line if at least one device required it.
The duration of the pull up is the max time required by a device on the
line, which depends on the resolution settings of each device. The strong
pull up could be adjust with the a module parameter.
Updating documentation in Documentation/ABI/testing/sysfs-driver-w1_therm
and Documentation/w1/slaves/w1_therm.rst accordingly.
Signed-off-by: Akira Shimahara <akira215corp@gmail.com>
Link: https://lore.kernel.org/r/20200511203820.411483-1-akira215corp@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
117 lines
4.4 KiB
Plaintext
117 lines
4.4 KiB
Plaintext
What: /sys/bus/w1/devices/.../alarms
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(RW) read or write TH and TL (Temperature High an Low) alarms.
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Values shall be space separated and in the device range
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(typical -55 degC to 125 degC), if not values will be trimmed
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to device min/max capabilities. Values are integer as they are
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stored in a 8bit register in the device. Lowest value is
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automatically put to TL. Once set, alarms could be search at
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master level, refer to Documentation/w1/w1_generic.rst for
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detailed information
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Users: any user space application which wants to communicate with
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w1_term device
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What: /sys/bus/w1/devices/.../eeprom
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(WO) writing that file will either trigger a save of the
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device data to its embedded EEPROM, either restore data
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embedded in device EEPROM. Be aware that devices support
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limited EEPROM writing cycles (typical 50k)
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* 'save': save device RAM to EEPROM
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* 'restore': restore EEPROM data in device RAM
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Users: any user space application which wants to communicate with
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w1_term device
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What: /sys/bus/w1/devices/.../ext_power
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(RO) return the power status by asking the device
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* '0': device parasite powered
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* '1': device externally powered
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* '-xx': xx is kernel error when reading power status
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Users: any user space application which wants to communicate with
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w1_term device
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What: /sys/bus/w1/devices/.../resolution
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(RW) get or set the device resolution (on supported devices,
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if not, this entry is not present). Note that the resolution
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will be changed only in device RAM, so it will be cleared when
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power is lost. Trigger a 'save' to EEPROM command to keep
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values after power-on. Read or write are :
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* '9..12': device resolution in bit
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or resolution to set in bit
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* '-xx': xx is kernel error when reading the resolution
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* Anything else: do nothing
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Users: any user space application which wants to communicate with
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w1_term device
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What: /sys/bus/w1/devices/.../temperature
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(RO) return the temperature in 1/1000 degC.
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* If a bulk read has been triggered, it will directly
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return the temperature computed when the bulk read
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occurred, if available. If not yet available, nothing
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is returned (a debug kernel message is sent), you
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should retry later on.
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* If no bulk read has been triggered, it will trigger
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a conversion and send the result. Note that the
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conversion duration depend on the resolution (if
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device support this feature). It takes 94ms in 9bits
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resolution, 750ms for 12bits.
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Users: any user space application which wants to communicate with
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w1_term device
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What: /sys/bus/w1/devices/.../w1_slave
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(RW) return the temperature in 1/1000 degC.
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*read*: return 2 lines with the hexa output data sent on the
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bus, return the CRC check and temperature in 1/1000 degC
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*write* :
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* '0' : save the 2 or 3 bytes to the device EEPROM
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(i.e. TH, TL and config register)
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* '9..12' : set the device resolution in RAM
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(if supported)
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* Anything else: do nothing
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refer to Documentation/w1/slaves/w1_therm.rst for detailed
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information.
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Users: any user space application which wants to communicate with
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w1_term device
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What: /sys/bus/w1/devices/w1_bus_masterXX/therm_bulk_read
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Date: May 2020
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Contact: Akira Shimahara <akira215corp@gmail.com>
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Description:
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(RW) trigger a bulk read conversion. read the status
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*read*:
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* '-1': conversion in progress on at least 1 sensor
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* '1' : conversion complete but at least one sensor
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value has not been read yet
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* '0' : no bulk operation. Reading temperature will
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trigger a conversion on each device
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*write*: 'trigger': trigger a bulk read on all supporting
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devices on the bus
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Note that if a bulk read is sent but one sensor is not read
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immediately, the next access to temperature on this device
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will return the temperature measured at the time of issue
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of the bulk read command (not the current temperature).
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Users: any user space application which wants to communicate with
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w1_term device
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