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Diffstat (limited to 'Documentation/w1/slaves/w1_ds28e17')
| -rw-r--r-- | Documentation/w1/slaves/w1_ds28e17 | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/Documentation/w1/slaves/w1_ds28e17 b/Documentation/w1/slaves/w1_ds28e17 new file mode 100644 index 000000000000..7fcfad5b4a37 --- /dev/null +++ b/Documentation/w1/slaves/w1_ds28e17 @@ -0,0 +1,68 @@ +Kernel driver w1_ds28e17 +======================== + +Supported chips: + * Maxim DS28E17 1-Wire-to-I2C Master Bridge + +supported family codes: + W1_FAMILY_DS28E17 0x19 + +Author: Jan Kandziora <jjj@gmx.de> + + +Description +----------- +The DS28E17 is a Onewire slave device which acts as an I2C bus master. + +This driver creates a new I2C bus for any DS28E17 device detected. I2C buses +come and go as the DS28E17 devices come and go. I2C slave devices connected to +a DS28E17 can be accessed by the kernel or userspace tools as if they were +connected to a "native" I2C bus master. + + +An udev rule like the following +------------------------------------------------------------------------------- +SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \ + SYMLINK+="i2c-$attr{name}" +------------------------------------------------------------------------------- +may be used to create stable /dev/i2c- entries based on the unique id of the +DS28E17 chip. + + +Driver parameters are: + +speed: + This sets up the default I2C speed a DS28E17 get configured for as soon + it is connected. The power-on default of the DS28E17 is 400kBaud, but + chips may come and go on the Onewire bus without being de-powered and + as soon the "w1_ds28e17" driver notices a freshly connected, or + reconnected DS28E17 device on the Onewire bus, it will re-apply this + setting. + + Valid values are 100, 400, 900 [kBaud]. Any other value means to leave + alone the current DS28E17 setting on detect. The default value is 100. + +stretch: + This sets up the default stretch value used for freshly connected + DS28E17 devices. It is a multiplier used on the calculation of the busy + wait time for an I2C transfer. This is to account for I2C slave devices + which make heavy use of the I2C clock stretching feature and thus, the + needed timeout cannot be pre-calculated correctly. As the w1_ds28e17 + driver checks the DS28E17's busy flag in a loop after the precalculated + wait time, it should be hardly needed to tweak this setting. + + Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver + 19-00000002dbd8: busy timeout" in the kernel log. + + Valid values are 1 to 9. The default is 1. + + +The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and +/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default +settings from the driver parameters. They may be changed anytime. In addition a +directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs +structure is created. + + +See https://github.com/ianka/w1_ds28e17 for even more information. + |