[GitHub/MotorolaMobilityLLC/kernel-slsi.git] / Documentation / w1 / slaves / w1_ds2406

w1_ds2406 kernel driver
=======================

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

Author: Scott Alfter <scott@alfter.us>

Description
-----------

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.
Commit	Line	Data
94859308 SA	1	w1_ds2406 kernel driver
	2	=======================
	3
	4	Supported chips:
	5	* Maxim DS2406 (and other family 0x12) addressable switches
	6
	7	Author: Scott Alfter <scott@alfter.us>
	8
	9	Description
	10	-----------
	11
	12	The w1_ds2406 driver allows connected devices to be switched on and off.
	13	These chips also provide 128 bytes of OTP EPROM, but reading/writing it is
	14	not supported. In TSOC-6 form, the DS2406 provides two switch outputs and
	15	can be provided with power on a dedicated input. In TO-92 form, it provides
	16	one output and uses parasitic power only.
	17
	18	The driver provides two sysfs files. state is readable; it gives the
	19	current state of each switch, with PIO A in bit 0 and PIO B in bit 1. The
	20	driver ORs this state with 0x30, so shell scripts get an ASCII 0/1/2/3 to
	21	work with. output is writable; bits 0 and 1 control PIO A and B,
	22	respectively. Bits 2-7 are ignored, so it's safe to write ASCII data.
	23
	24	CRCs are checked on read and write. Failed checks cause an I/O error to be
	25	returned. On a failed write, the switch status is not changed.