162306a36Sopenharmony_ci=======================
262306a36Sopenharmony_ciw1_ds2406 kernel driver
362306a36Sopenharmony_ci=======================
462306a36Sopenharmony_ci
562306a36Sopenharmony_ciSupported chips:
662306a36Sopenharmony_ci
762306a36Sopenharmony_ci  * Maxim DS2406 (and other family 0x12) addressable switches
862306a36Sopenharmony_ci
962306a36Sopenharmony_ciAuthor: Scott Alfter <scott@alfter.us>
1062306a36Sopenharmony_ci
1162306a36Sopenharmony_ciDescription
1262306a36Sopenharmony_ci-----------
1362306a36Sopenharmony_ci
1462306a36Sopenharmony_ciThe w1_ds2406 driver allows connected devices to be switched on and off.
1562306a36Sopenharmony_ciThese chips also provide 128 bytes of OTP EPROM, but reading/writing it is
1662306a36Sopenharmony_cinot supported.  In TSOC-6 form, the DS2406 provides two switch outputs and
1762306a36Sopenharmony_cican be provided with power on a dedicated input.  In TO-92 form, it provides
1862306a36Sopenharmony_cione output and uses parasitic power only.
1962306a36Sopenharmony_ci
2062306a36Sopenharmony_ciThe driver provides two sysfs files.  state is readable; it gives the
2162306a36Sopenharmony_cicurrent state of each switch, with PIO A in bit 0 and PIO B in bit 1.  The
2262306a36Sopenharmony_cidriver ORs this state with 0x30, so shell scripts get an ASCII 0/1/2/3 to
2362306a36Sopenharmony_ciwork with.  output is writable; bits 0 and 1 control PIO A and B,
2462306a36Sopenharmony_cirespectively.  Bits 2-7 are ignored, so it's safe to write ASCII data.
2562306a36Sopenharmony_ci
2662306a36Sopenharmony_ciCRCs are checked on read and write.  Failed checks cause an I/O error to be
2762306a36Sopenharmony_cireturned.  On a failed write, the switch status is not changed.
28