ethernet<n> dt aliases implications in U-Boot and Linux

[Sean Anderson]

On 8/8/22 5:45 PM, Michal Suchánek wrote:
> On Mon, Aug 08, 2022 at 02:38:35PM -0700, Stephen Hemminger wrote:
>> On Mon, 8 Aug 2022 23:09:45 +0200
>> Michal Suchánek <msuchanek at suse.de> wrote:
>> 
>> > On Mon, Aug 08, 2022 at 03:57:55PM -0400, Sean Anderson wrote:
>> > > Hi Tim,
>> > > 
>> > > On 8/8/22 3:18 PM, Tim Harvey wrote:  
>> > > > Greetings,
>> > > > 
>> > > > I'm trying to understand if there is any implication of 'ethernet<n>'
>> > > > aliases in Linux such as:
>> > > >         aliases {
>> > > >                 ethernet0 = &eqos;
>> > > >                 ethernet1 = &fec;
>> > > >                 ethernet2 = &lan1;
>> > > >                 ethernet3 = &lan2;
>> > > >                 ethernet4 = &lan3;
>> > > >                 ethernet5 = &lan4;
>> > > >                 ethernet6 = &lan5;
>> > > >         };
>> > > > 
>> > > > I know U-Boot boards that use device-tree will use these aliases to
>> > > > name the devices in U-Boot such that the device with alias 'ethernet0'
>> > > > becomes eth0 and alias 'ethernet1' becomes eth1 but for Linux it
>> > > > appears that the naming of network devices that are embedded (ie SoC)
>> > > > vs enumerated (ie pci/usb) are always based on device registration
>> > > > order which for static drivers depends on Makefile linking order and
>> > > > has nothing to do with device-tree.
>> > > > 
>> > > > Is there currently any way to control network device naming in Linux
>> > > > other than udev?  
>> > > 
>> > > You can also use systemd-networkd et al. (but that is the same kind of mechanism)
>> > >   
>> > > > Does Linux use the ethernet<n> aliases for anything at all?  
>> > > 
>> > > No :l  
>> > 
>> > Maybe it's a great opportunity for porting biosdevname to DT based
>> > platforms ;-)
>> 
>> Sorry, biosdevname was wrong way to do things.
>> Did you look at the internals, it was dumpster diving as root into BIOS.
> 
> When it's BIOS what defines the names then you have to read them from
> the BIOS. Recently it was updated to use some sysfs file or whatver.
> It's not like you would use any of that code with DT, anyway.
> 
>> Systemd-networkd does things in much more supportable manner using existing
>> sysfs API's.
> 
> Which is a dumpster of systemd code, no thanks.
> 
> I want my device naming independent of the init system, especially if
> it's systemd.

Well, there's always nameif...

That said, I have made [1] for people using systemd-networkd.

--Sean

[1] https://github.com/systemd/systemd/pull/24265