Re: [gentoo-user] Re: udev (viable) alternatives ?

[Samuli Suominen <ssuominen@gentoo.org>]

On 26/09/14 11:47, Samuli Suominen wrote:
> On 26/09/14 11:22, Canek Peláez Valdés wrote:
>> On Fri, Sep 26, 2014 at 3:07 AM, Neil Bothwick <neil@digimed.co.uk> wrote:
>>> On Fri, 26 Sep 2014 05:27:15 +0200, Alan McKinnon wrote:
>>>
>>>>>   I buy machines with one ethernet interface.  What I find
>>>>> particularly annoying is this doublespeak about calling it
>>>>> "predictable".  Before the change, it was predicatbly "eth0".  Now,
>>>>> it's different on every different model.
>>>> It's not doublespeak, the interfaces are named exactly according to
>>>> where they are on the PCI bus. If you had two interfaces, they show up
>>>> to the kernel in random order by time and sometimes eth0/eth1 are nto
>>>> the same they were before the reboot.
>>> That may be true for PCI devices but not for USB ones. If you unplug a
>>> USB device and plug it back into the same port, it will get a different
>>> device number. The naming is more predictable, but it's not there yet.
>> That doesn't sound right. If unplugging a USB net device and plugging
>> it again *in the same port* results in a different device *name*, then
>> it is a bug and should be reported; the description of the algorithm
>> in [1] sounds like it should get always the same name for the same
>> port, unless I'm misunderstanding something.
>>
>> Regards.
>>
>> [1] http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n51
> I've seen this happening once on a cheap laptop with a stripped down
> BIOS I can't
> even recall brand for, it had a kludge in the BIOS settings for
> hotplugging, turning
> it off, allowed the port to remain same, turning it on, some machine
> specific code
> gets executed and the kernel interprets the same port as different port
>
> Bad hardware, bad hardware settings, maybe missing exception for that
> particular
> hardware type in the code that determines the name... I'm not sure, I
> don't have
> the machine anymore
>
> - Samuli
>

Later kernels *can mark interfaces predictable in a new form of
metadata*, and udev >= 209 can
pick that information up, and then it won't do anykind of userspace
renaming on it, since kernel
has declared the interface name to be steady...predictable...always
same, so I hope
we are moving towards kernel assigning predictable names for all drivers
and we can get rid of
the userspace renaming of interfaces all together at some point
I really believe this is a task for the kernel to provide predictable
names, and all this userspace
renaming is just a bandage we can hopefully soon rip off

- Samuli