[systemd-devel] Match section of .link file not working

[Tom Gundersen]

On Mon, Aug 25, 2014 at 9:49 PM, Marcel Holtmann <marcel at holtmann.org> wrote:
> Hi Tom,
>
>>>>>>>> This should be the value of ID_PATH property, not sysfs path. Check with
>>>>>>>>
>>>>>>>> udevadm info --query
>>>>>>>> property /sys/devices/ocp.3/47400000.usb/musb-hdrc.1.auto/usb1/1-1/1-1:1.0/net/wlv3
>>>>>>>
>>>>>>> oops, I confused ID_PATH with DEVPATH, now i feel like an idiot.
>>>>>
>>>>> ID_PATH is basically the "reduced + stable" part of the full sysfs path.
>>>>>
>>>>>> Ok, so there is only one problem now:
>>>>>> ID_PATH is the same for all my vif interfaces, and i need to select
>>>>>> only one of them.
>>>>
>>>> ID_PATH usually describes the "parent hardware", and the same hardware
>>>> can have multiple independent devices. Unique names for several
>>>> devices need to be composed by appending something to the "parent
>>>> hardware".
>>>>
>>>> I don't have a good idea what a working model for your case would be,
>>>> where multiple devices share the same parent. This is not a common
>>>> model.
>>>>
>>>>> This is some embedded device with your hw connected to some platform
>>>>> bus?
>>>>>
>>>>> Currently the ID_PATH logic doesn't understand platform busses (since it
>>>>> is not clear how "stable" they are). This has come up before, and could
>>>>> probably be fixed. Maybe we should assume that platform busses are
>>>>> always enuemrated in a stable way, dunno.
>>>>>
>>>>> Kay probably has something useful to say here. Kay?
>>>>
>>>> Special buses need explicit support in the code if ID_PATH is not
>>>> generated, but that does not look like the problem here.
>>>>
>>>> Seems the USB interface exports 3 different network devices. Do they
>>>> have any unique property? Like dev_id, dev_port in /sys? Or are the
>>>> types of the netifs unique?
>>>
>>> Well, as posted earlier , these are virtual interfaces, kind of the
>>> vlans for wifi (allows to connect ot multiple networks on a same phy).
>>> (sory for not precise enough in the original post)
>>> So they do not realy have something unique and stable appart from the name.
>>>
>>> I think there are 3 posible ways to go forward:
>>> - fix iw (and maybe the kernel to) to support a mac address parameter
>>> at interface creation time (so the mac is set even before udev sees
>>> it)
>>
>> I really think this is the correct way to go. If something is being
>> created from userspace, it should just be created correctly in the
>> first place.
>
> there has been a discussion on the wireless mailing list about exactly this topic. Currently nl80211 only allows MAC address setup for P2P devices, but the general agreement is that this should be extended to allow for any interfaces. This is also useful for hardware that has not pre-configured MAC address and where the address needs to be provided by userspace anyway.
>
> So this fix should be for the NL80211_CMD_NEW_INTERFACE to handle providing the MAC address for all interface types.


Thanks Marcel, that's good to know!

Cheers,

Tom