udev and w1/wire

udev and w1/wire

[Max Hille]

I want to use a 1-wire slave device from user space.

My first approach is to get a symlink like /dev/wire-slave with user
read/write permissions. I have tried this with udev rules but didn't
get it to work so far.

Some additional information about the wire kernel module:
Module name: wire (available in stock Ubuntu 13,04)
Subsystem: w1
creates the following in /sys/:
devices/w1_bus_master1/81-XXXXXXXXXXXX/
where the 81 is a slave device specific identifier. Inside that
directory is a file(?) named "rw" which I can (successfully) use to
communicate with the onewire device.

I have already managed to write a udev rule which sets the permissions
on this "rw" so I can use it from user space. But then I have my
program to search through /sys/ to access the device which does not
seems to be the right way (eg. did not work on my friends Linux Mint).

If it is not possible to create a device node in /dev, I'd be thankful
for alternative solutions.

-- Max

Re: udev and w1/wire

[Greg KH]

On Sat, Oct 05, 2013 at 12:21:52PM +0200, Max Hille wrote:
> I want to use a 1-wire slave device from user space.
> 
> My first approach is to get a symlink like /dev/wire-slave with user
> read/write permissions. I have tried this with udev rules but didn't
> get it to work so far.
> 
> Some additional information about the wire kernel module:
> Module name: wire (available in stock Ubuntu 13,04)
> Subsystem: w1
> creates the following in /sys/:
> devices/w1_bus_master1/81-XXXXXXXXXXXX/
> where the 81 is a slave device specific identifier. Inside that
> directory is a file(?) named "rw" which I can (successfully) use to
> communicate with the onewire device.
> 
> I have already managed to write a udev rule which sets the permissions
> on this "rw" so I can use it from user space. But then I have my
> program to search through /sys/ to access the device which does not
> seems to be the right way (eg. did not work on my friends Linux Mint).
> 
> If it is not possible to create a device node in /dev, I'd be thankful
> for alternative solutions.

Just use the sysfs file, this driver does not use any device node it
seems, so no need to try to create one that doesn't exist.

Also, the w1 interface is usually through the "connector" subsystem,
which is a network protocol, not a device node.  What is wrong with
using that?

greg k-h