Proposed F19 Feature: systemd/udev Predictable Network Interface Names

[Kay Sievers]

On Mon, Mar 4, 2013 at 6:01 PM, Andy Gospodarek <agospoda at redhat.com> wrote:
> On Mon, Mar 04, 2013 at 10:19:14AM -0600, Matt Domsch wrote:

>> > > drivers/net/ethernet/mellanox/mlx4/en_netdev.c: dev->dev_id =  port - 1;
>> > > drivers/net/ethernet/sfc/siena.c:       efx->net_dev->dev_id = EFX_OWORD_FIELD(reg, FRF_CZ_CS_PORT_NUM) - 1;
>> > >
>> > > of these, both the mlx4 and siena drivers set them starting at 0.  I
>> > > think the fec driver might be doing so as well, but it's not as
>> > > obvious.  I'm pretty sure cxgb4 starts numbering at 1 just from
>> > > reading the code.  So, as-is in the 3.9rc1 kernel, I wouldn't be
>> > > comfortable relying on the value of dev_id.
>> >
>> > I agree it looks like some cleanup is needed due to the inconsistency.
>> >
>> > This is still only an issue when a single function supports multiple
>> > ethernet devices, right?
>>
>> I believe so, yes.
>
> Ok, good.  I did like your idea to possibly set this to something other
> than 0 in the default case and then make sure that any driver that needs
> to set it can do so.

The udev code just appends the dev_id number to the device name if
dev_id is > 0, so either starting at 0 or at 1 would work fine and
produce reliable results.

Starting at 1 would create slightly more consistent names, where all
names of one and the same card follow the same scheme, and 0 is not
special because it is suppressed.

Kay