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| author | Akira Shimahara <akira215corp@gmail.com> | 2020-05-11 23:36:50 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-05-15 17:28:59 +0300 |
| commit | b7bb6ca17a90f47c2fe2848531b5bbaf27a65ba7 (patch) | |
| tree | 89033d9538960d02e369f5164246f455dfb545c0 /Documentation/ABI/testing/sysfs-driver-w1_therm | |
| parent | daa3cfeb1971fd07b9c00ce452b3e3ff3298fa13 (diff) | |
| download | linux-b7bb6ca17a90f47c2fe2848531b5bbaf27a65ba7.tar.xz | |
w1_therm: adding ext_power sysfs entry
Adding ext_power sysfs entry (RO). Return the power status of the device:
- 0: device parasite powered
- 1: device externally powered
- xx: xx is kernel error
The power status 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 power state of each device, which could
be used later to determine the required strong pull up to apply on the
line.
The power status is re evaluate each time the sysfs ext_power read by
a user.
The hardware function 'read_powermode(struct w1_slave *sl)' act just as
per device specifications, sending W1_READ_PSUPPLY command on the bus,
and issue a read time slot, reading only one bit.
A helper function 'bool bus_mutex_lock(struct mutex *lock)' is introduced.
It try to aquire the bus mutex several times (W1_THERM_MAX_TRY), waiting
W1_THERM_RETRY_DELAY between two attempt.
Updating Documentation/ABI/testing/sysfs-driver-w1_therm accordingly.
Signed-off-by: Akira Shimahara <akira215corp@gmail.com>
Link: https://lore.kernel.org/r/20200511203650.410439-1-akira215corp@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/ABI/testing/sysfs-driver-w1_therm')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-driver-w1_therm | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-driver-w1_therm b/Documentation/ABI/testing/sysfs-driver-w1_therm index 4a856631aaf9..99d73eeee3db 100644 --- a/Documentation/ABI/testing/sysfs-driver-w1_therm +++ b/Documentation/ABI/testing/sysfs-driver-w1_therm @@ -1,3 +1,15 @@ +What: /sys/bus/w1/devices/.../ext_power +Date: May 2020 +Contact: Akira Shimahara <akira215corp@gmail.com> +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/.../w1_slave Date: May 2020 Contact: Akira Shimahara <akira215corp@gmail.com> |