mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-26 04:45:36 +07:00
ebc4768ac4
This subpatch adds a driver for the DS28E17 Onewire to I2C master bridge. Signed-off-by: Jan Kandziora <jjj@gmx.de> Acked-by: Evgeniy Polyakov <zbr@ioremap.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
69 lines
2.5 KiB
Plaintext
69 lines
2.5 KiB
Plaintext
Kernel driver w1_ds28e17
|
|
========================
|
|
|
|
Supported chips:
|
|
* Maxim DS28E17 1-Wire-to-I2C Master Bridge
|
|
|
|
supported family codes:
|
|
W1_FAMILY_DS28E17 0x19
|
|
|
|
Author: Jan Kandziora <jjj@gmx.de>
|
|
|
|
|
|
Description
|
|
-----------
|
|
The DS28E17 is a Onewire slave device which acts as an I2C bus master.
|
|
|
|
This driver creates a new I2C bus for any DS28E17 device detected. I2C buses
|
|
come and go as the DS28E17 devices come and go. I2C slave devices connected to
|
|
a DS28E17 can be accessed by the kernel or userspace tools as if they were
|
|
connected to a "native" I2C bus master.
|
|
|
|
|
|
An udev rule like the following
|
|
-------------------------------------------------------------------------------
|
|
SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \
|
|
SYMLINK+="i2c-$attr{name}"
|
|
-------------------------------------------------------------------------------
|
|
may be used to create stable /dev/i2c- entries based on the unique id of the
|
|
DS28E17 chip.
|
|
|
|
|
|
Driver parameters are:
|
|
|
|
speed:
|
|
This sets up the default I2C speed a DS28E17 get configured for as soon
|
|
it is connected. The power-on default of the DS28E17 is 400kBaud, but
|
|
chips may come and go on the Onewire bus without being de-powered and
|
|
as soon the "w1_ds28e17" driver notices a freshly connected, or
|
|
reconnected DS28E17 device on the Onewire bus, it will re-apply this
|
|
setting.
|
|
|
|
Valid values are 100, 400, 900 [kBaud]. Any other value means to leave
|
|
alone the current DS28E17 setting on detect. The default value is 100.
|
|
|
|
stretch:
|
|
This sets up the default stretch value used for freshly connected
|
|
DS28E17 devices. It is a multiplier used on the calculation of the busy
|
|
wait time for an I2C transfer. This is to account for I2C slave devices
|
|
which make heavy use of the I2C clock stretching feature and thus, the
|
|
needed timeout cannot be pre-calculated correctly. As the w1_ds28e17
|
|
driver checks the DS28E17's busy flag in a loop after the precalculated
|
|
wait time, it should be hardly needed to tweak this setting.
|
|
|
|
Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver
|
|
19-00000002dbd8: busy timeout" in the kernel log.
|
|
|
|
Valid values are 1 to 9. The default is 1.
|
|
|
|
|
|
The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and
|
|
/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default
|
|
settings from the driver parameters. They may be changed anytime. In addition a
|
|
directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs
|
|
structure is created.
|
|
|
|
|
|
See https://github.com/ianka/w1_ds28e17 for even more information.
|
|
|