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w1_ds2406 kernel driver
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Supported chips:

  * Maxim DS2406 (and other family 0x12) addressable switches

Author: Scott Alfter <scott@alfter.us>

Description
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The w1_ds2406 driver allows connected devices to be switched on and off.
These chips also provide 128 bytes of OTP EPROM, but reading/writing it is
not supported.  In TSOC-6 form, the DS2406 provides two switch outputs and
can be provided with power on a dedicated input.  In TO-92 form, it provides
one output and uses parasitic power only.

The driver provides two sysfs files.  state is readable; it gives the
current state of each switch, with PIO A in bit 0 and PIO B in bit 1.  The
driver ORs this state with 0x30, so shell scripts get an ASCII 0/1/2/3 to
work with.  output is writable; bits 0 and 1 control PIO A and B,
respectively.  Bits 2-7 are ignored, so it's safe to write ASCII data.

CRCs are checked on read and write.  Failed checks cause an I/O error to be
returned.  On a failed write, the switch status is not changed.