308bdb94de
Adding resolution sysfs entry (RW) to get or set the device resolution Write values are managed as follow: * '9..12': resolution to set in bit * Anything else: do nothing Read values are : * '9..12': device resolution in bit * '-xx': xx is kernel error when reading the resolution Only supported devices will show the sysfs entry. A new family has been created for DS18S20 devices as they do not implement resolution feature. The resolution of each device is check when the device is discover by the bus master, in 'w1_therm_add_slave(struct w1_slave *)'. The status is stored in the device structure w1_therm_family_data so that the driver always knows the resolution of each device, which could be used later to determine the required conversion duration (resolution dependent). The resolution is re evaluate each time a user read or write the sysfs entry. To avoid looping through the w1_therm_families at run time, the pointer 'specific_functions' is set up to the correct 'w1_therm_family_converter' when the slave is added (which mean when it is discovered by the master). This initialization is done by a helper function 'device_family(struct w1_slave *sl)', and a dedicated macro 'SLAVE_SPECIFIC_FUNC(sl)' allow the access to the specific function of the slave device. 'read_scratchpad' and 'write_scratchpad' are the hardware functions to access the device RAM, as per protocol specification. It cancel the former 'precision' functions, which was only set and never read (so not stored in the device struct). Updating Documentation/ABI/testing/sysfs-driver-w1_therm accordingly. Signed-off-by: Akira Shimahara <akira215corp@gmail.com> Link: https://lore.kernel.org/r/20200511203708.410649-1-akira215corp@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
46 lines
1.7 KiB
Plaintext
46 lines
1.7 KiB
Plaintext
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/.../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 |