mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 19:00:25 +00:00
![Mauro Carvalho Chehab](/assets/img/avatar_default.png)
The 1wire documentation was written with w1 developers in mind, so, it makes sense to add it together with the driver-api set. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
59 lines
1.8 KiB
ReStructuredText
59 lines
1.8 KiB
ReStructuredText
=======================
|
|
Kernel driver w1_ds2413
|
|
=======================
|
|
|
|
Supported chips:
|
|
|
|
* Maxim DS2413 1-Wire Dual Channel Addressable Switch
|
|
|
|
supported family codes:
|
|
|
|
================ ====
|
|
W1_FAMILY_DS2413 0x3A
|
|
================ ====
|
|
|
|
Author: Mariusz Bialonczyk <manio@skyboo.net>
|
|
|
|
Description
|
|
-----------
|
|
|
|
The DS2413 chip has two open-drain outputs (PIO A and PIO B).
|
|
Support is provided through the sysfs files "output" and "state".
|
|
|
|
Reading state
|
|
-------------
|
|
The "state" file provides one-byte value which is in the same format as for
|
|
the chip PIO_ACCESS_READ command (refer the datasheet for details):
|
|
|
|
======== =============================================================
|
|
Bit 0: PIOA Pin State
|
|
Bit 1: PIOA Output Latch State
|
|
Bit 2: PIOB Pin State
|
|
Bit 3: PIOB Output Latch State
|
|
Bit 4-7: Complement of Bit 3 to Bit 0 (verified by the kernel module)
|
|
======== =============================================================
|
|
|
|
This file is readonly.
|
|
|
|
Writing output
|
|
--------------
|
|
You can set the PIO pins using the "output" file.
|
|
It is writable, you can write one-byte value to this sysfs file.
|
|
Similarly the byte format is the same as for the PIO_ACCESS_WRITE command:
|
|
|
|
======== ======================================
|
|
Bit 0: PIOA
|
|
Bit 1: PIOB
|
|
Bit 2-7: No matter (driver will set it to "1"s)
|
|
======== ======================================
|
|
|
|
|
|
The chip has some kind of basic protection against transmission errors.
|
|
When reading the state, there is a four complement bits.
|
|
The driver is checking this complement, and when it is wrong then it is
|
|
returning I/O error.
|
|
|
|
When writing output, the master must repeat the PIO Output Data byte in
|
|
its inverted form and it is waiting for a confirmation.
|
|
If the write is unsuccessful for three times, the write also returns
|
|
I/O error.
|