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Commit ebc4768a authored by Jan Kandziora's avatar Jan Kandziora Committed by Greg Kroah-Hartman
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add w1_ds28e17 driver for the DS28E17 Onewire to I2C master bridge 



This subpatch adds a driver for the DS28E17 Onewire to I2C master bridge.

Signed-off-by: default avatarJan Kandziora <jjj@gmx.de>
Acked-by: default avatarEvgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent eb8470db

Documentation/ABI/testing/sysfs-driver-w1_ds28e17

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What:		/sys/bus/w1/devices/19-<id>/speed

Date:		Sep 2017

KernelVersion:	4.14

Contact:	Jan Kandziora <jjj@gmx.de>

Description:	When written, this file sets the I2C speed on the connected

		DS28E17 chip. When read, it reads the current setting from

		the DS28E17 chip.

		Valid values: 100, 400, 900 [kBaud].

		Default 100, can be set by w1_ds28e17.speed= module parameter.

Users:		w1_ds28e17 driver



What:		/sys/bus/w1/devices/19-<id>/stretch

Date:		Sep 2017

KernelVersion:	4.14

Contact:	Jan Kandziora <jjj@gmx.de>

Description:	When written, this file sets the multiplier used to calculate

		the busy timeout for I2C operations on the connected DS28E17

		chip. When read, returns the current setting.

		Valid values: 1 to 9.

		Default 1, can be set by w1_ds28e17.stretch= module parameter.

Users:		w1_ds28e17 driver

Documentation/w1/slaves/00-INDEX

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@@ -10,3 +10,5 @@ w1_ds2438 
	- The Maxim/Dallas Semiconductor ds2438 smart battery monitor.

w1_ds28e04

	- The Maxim/Dallas Semiconductor ds28e04 eeprom.

w1_ds28e17

	- The Maxim/Dallas Semiconductor ds28e17 1-Wire-to-I2C Master Bridge.

Documentation/w1/slaves/w1_ds28e17

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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.

drivers/w1/slaves/Kconfig

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@@ -148,4 +148,19 @@ config W1_SLAVE_DS28E04 


	  If you are unsure, say N.



config W1_SLAVE_DS28E17

	tristate "1-wire-to-I2C master bridge (DS28E17)"

	select CRC16

	depends on I2C

	help

	  Say Y here if you want to use the DS28E17 1-wire-to-I2C master bridge.

	  For each DS28E17 detected, a new I2C adapter is created within the

	  kernel. I2C devices on that bus can be configured to be used by the

	  kernel and userspace tools as on any other "native" I2C bus.



	  This driver is also available as a module. If so, the module

	  will be called w1_ds28e17.



	  If you are unsure, say N.



endmenu

drivers/w1/slaves/Makefile

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@@ -17,3 +17,4 @@ obj-$(CONFIG_W1_SLAVE_DS2760) += w1_ds2760.o 
obj-$(CONFIG_W1_SLAVE_DS2780)	+= w1_ds2780.o

obj-$(CONFIG_W1_SLAVE_DS2781)	+= w1_ds2781.o

obj-$(CONFIG_W1_SLAVE_DS28E04)	+= w1_ds28e04.o

obj-$(CONFIG_W1_SLAVE_DS28E17)	+= w1_ds28e17.o