1========================
2Kernel driver w1_ds28e17
3========================
4
5Supported chips:
6
7  * Maxim DS28E17 1-Wire-to-I2C Master Bridge
8
9supported family codes:
10
11        =================  ====
12	W1_FAMILY_DS28E17  0x19
13        =================  ====
14
15Author: Jan Kandziora <jjj@gmx.de>
16
17
18Description
19-----------
20The DS28E17 is a Onewire slave device which acts as an I2C bus master.
21
22This driver creates a new I2C bus for any DS28E17 device detected. I2C buses
23come and go as the DS28E17 devices come and go. I2C slave devices connected to
24a DS28E17 can be accessed by the kernel or userspace tools as if they were
25connected to a "native" I2C bus master.
26
27
28An udev rule like the following::
29
30  SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \
31          SYMLINK+="i2c-$attr{name}"
32
33may be used to create stable /dev/i2c- entries based on the unique id of the
34DS28E17 chip.
35
36
37Driver parameters are:
38
39speed:
40	This sets up the default I2C speed a DS28E17 get configured for as soon
41	it is connected. The power-on default	of the DS28E17 is 400kBaud, but
42	chips may come and go on the Onewire bus without being de-powered and
43	as soon the "w1_ds28e17" driver notices a freshly connected, or
44	reconnected DS28E17 device on the Onewire bus, it will re-apply this
45	setting.
46
47	Valid values are 100, 400, 900 [kBaud]. Any other value means to leave
48	alone the current DS28E17 setting on detect. The default value is 100.
49
50stretch:
51	This sets up the default stretch value used for freshly connected
52	DS28E17 devices. It is a multiplier used on the calculation of the busy
53	wait time for an I2C transfer. This is to account for I2C slave devices
54	which make heavy use of the I2C clock stretching feature and thus, the
55	needed timeout cannot be pre-calculated correctly. As the w1_ds28e17
56	driver checks the DS28E17's busy flag in a loop after the precalculated
57	wait time, it should be hardly needed to tweak this setting.
58
59	Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver
60	19-00000002dbd8: busy timeout" in the kernel log.
61
62	Valid values are 1 to 9. The default is 1.
63
64
65The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and
66/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default
67settings from the driver parameters. They may be changed anytime. In addition a
68directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs
69structure is created.
70
71
72See https://github.com/ianka/w1_ds28e17 for even more information.
73