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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-17 16:22:26 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-17 16:22:26 -0700 |
commit | 7c672abc120a55f678e5571ae2ee93f06ca4d7f9 (patch) | |
tree | 7beebc09f9626ca8d5f7df4dded0a553de479323 /Documentation/w1/slaves/w1_ds28e17.rst | |
parent | 1902314157b19754e0ff25b44527654847cfd127 (diff) | |
parent | fe013f8bc160d79c6e33bb66d9bb0cd24949274c (diff) |
Merge tag 'docs-5.4' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"It's a somewhat calmer cycle for docs this time, as the churn of the
mass RST conversion is happily mostly behind us.
- A new document on reproducible builds.
- We finally got around to zapping the documentation for hardware
support that was removed in 2004; one doesn't want to rush these
things.
- The usual assortment of fixes, typo corrections, etc"
* tag 'docs-5.4' of git://git.lwn.net/linux: (67 commits)
Documentation: kbuild: Add document about reproducible builds
docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]
Documentation: Add "earlycon=sbi" to the admin guide
doc:lock: remove reference to clever use of read-write lock
devices.txt: improve entry for comedi (char major 98)
docs: mtd: Update spi nor reference driver
doc: arm64: fix grammar dtb placed in no attributes region
Documentation: sysrq: don't recommend 'S' 'U' before 'B'
mailmap: Update email address for Quentin Perret
docs: ftrace: clarify when tracing is disabled by the trace file
docs: process: fix broken link
Documentation/arm/samsung-s3c24xx: Remove stray U+FEFF character to fix title
Documentation/arm/sa1100/assabet: Fix 'make assabet_defconfig' command
Documentation/arm/sa1100: Remove some obsolete documentation
docs/zh_CN: update Chinese howto.rst for latexdocs making
Documentation: virt: Fix broken reference to virt tree's index
docs: Fix typo on pull requests guide
kernel-doc: Allow anonymous enum
Documentation: sphinx: Don't parse socket() as identifier reference
Documentation: sphinx: Add missing comma to list of strings
...
Diffstat (limited to 'Documentation/w1/slaves/w1_ds28e17.rst')
-rw-r--r-- | Documentation/w1/slaves/w1_ds28e17.rst | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/Documentation/w1/slaves/w1_ds28e17.rst b/Documentation/w1/slaves/w1_ds28e17.rst new file mode 100644 index 000000000000..e2d9f96d8f2c --- /dev/null +++ b/Documentation/w1/slaves/w1_ds28e17.rst @@ -0,0 +1,72 @@ +======================== +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. |