[systemd-devel] udev: problem renaming deviceode for dvb-devices

[Kay Sievers]

On Sat, Jun 23, 2012 at 2:17 PM, Dr. Thomas Bastian <tbastian at gmx.net> wrote:
>> Udev cannot rename kernel-created device nodes. These nodes are not
>> created by udev, but by the kernel itself. Udev will not change them,
>> just set permissions and ownership.
>>
>> Udev can add additional symlinks pointing to the kernel-created nodes.
>> Just use SYMLINK+= instead of NAME=, like here:
>>   http://cgit.freedesktop.org/systemd/systemd/tree/rules/60-persistent-v4l.rules
>
> thanks for your prompt reply. I understand your suggestion. But this
> does not help me to bring 4 dvb-cards
> (/dev/dvb/adapter0.../dev/dvb/adapter3) into the order needed for
> adressing the proper hardware by different apps, because the necessary
> symlinks have the same names as the kernel-given nodes (just another
> order).
>
> Are there other possibilities to make the kernel establish the nodenames
> based on hardware attributes rather then in the order of plugging the
> hardware into the computer?

Not really. Kernel names are not predictable in that manner. They are
simply unique numbers, no stability is guaranteed regarding
parallelism or discovery order.

The tools which relay on a specific name should use the symlinks
directly instead of looking at the plain kernel names.

Or they should be made aware to cope with different names at every
bootup, and select the devices on properties they find at the device,
instead of expecting the kernel's enumeration number to be stable.

Kay