1Kernel driver w1_ds28e17
2========================
3
4Supported chips:
5  * Maxim DS28E17 1-Wire-to-I2C Master Bridge
6
7supported family codes:
8	W1_FAMILY_DS28E17  0x19
9
10Author: Jan Kandziora <jjj@gmx.de>
11
12
13Description
14-----------
15The DS28E17 is a Onewire slave device which acts as an I2C bus master.
16
17This driver creates a new I2C bus for any DS28E17 device detected. I2C buses
18come and go as the DS28E17 devices come and go. I2C slave devices connected to
19a DS28E17 can be accessed by the kernel or userspace tools as if they were
20connected to a "native" I2C bus master.
21
22
23An udev rule like the following
24-------------------------------------------------------------------------------
25SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \
26        SYMLINK+="i2c-$attr{name}"
27-------------------------------------------------------------------------------
28may be used to create stable /dev/i2c- entries based on the unique id of the
29DS28E17 chip.
30
31
32Driver parameters are:
33
34speed:
35	This sets up the default I2C speed a DS28E17 get configured for as soon
36	it is connected. The power-on default	of the DS28E17 is 400kBaud, but
37	chips may come and go on the Onewire bus without being de-powered and
38	as soon the "w1_ds28e17" driver notices a freshly connected, or
39	reconnected DS28E17 device on the Onewire bus, it will re-apply this
40	setting.
41
42	Valid values are 100, 400, 900 [kBaud]. Any other value means to leave
43	alone the current DS28E17 setting on detect. The default value is 100.
44
45stretch:
46	This sets up the default stretch value used for freshly connected
47	DS28E17 devices. It is a multiplier used on the calculation of the busy
48	wait time for an I2C transfer. This is to account for I2C slave devices
49	which make heavy use of the I2C clock stretching feature and thus, the
50	needed timeout cannot be pre-calculated correctly. As the w1_ds28e17
51	driver checks the DS28E17's busy flag in a loop after the precalculated
52	wait time, it should be hardly needed to tweak this setting.
53
54	Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver
55	19-00000002dbd8: busy timeout" in the kernel log.
56
57	Valid values are 1 to 9. The default is 1.
58
59
60The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and
61/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default
62settings from the driver parameters. They may be changed anytime. In addition a
63directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs
64structure is created.
65
66
67See https://github.com/ianka/w1_ds28e17 for even more information.
68
69