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

[Sean Anderson]

On 8/9/22 5:42 PM, Pali Rohár wrote:
> On Tuesday 09 August 2022 17:36:52 Sean Anderson wrote:
>> On 8/9/22 5:31 PM, Pali Rohár wrote:
>> > On Tuesday 09 August 2022 16:48:23 Sean Anderson wrote:
>> >> 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
>> > 
>> > Hello!
>> > 
>> > In some cases "label" DT property can be used also as interface name.
>> > For example this property is already used by DSA kernel driver.
>> > 
>> > I created very simple script which renames all interfaces in system to
>> > their "label" DT property (if there is any defined).
>> > 
>> > #!/bin/sh
>> > for iface in `ls /sys/class/net/`; do
>> > 	for of_node in of_node device/of_node; do
>> > 		if test -e /sys/class/net/$iface/$of_node/; then
>> > 			label=`cat /sys/class/net/$iface/$of_node/label 2>/dev/null`
>> > 			if test -n "$label" && test "$label" != "$iface"; then
>> > 				echo "Renaming net interface $iface to $label..."
>> > 				up=$((`cat /sys/class/net/$iface/flags 2>/dev/null || echo 1` & 0x1))
>> > 				if test "$up" != "0"; then
>> > 					ip link set dev $iface down
>> > 				fi
>> > 				ip link set dev $iface name "$label" && iface=$label
>> > 				if test "$up" != "0"; then
>> > 					ip link set dev $iface up
>> > 				fi
>> > 			fi
>> > 			break
>> > 		fi
>> > 	done
>> > done
>> > 
>> > Maybe it would be better first to use "label" and then use ethernet alias?
>> > 
>> 
>> It looks like there is already precedent for using ID_NET_LABEL_ONBOARD for
>> this purpose (on SMBios boards). It should be a fairly simple extension to
>> add that as well. However, I didn't find any uses of this in Linux or U-Boot
>> (although I did find plenty of ethernet LEDs). Do you have an example you
>> could point me to?
>> 
>> --Sean
> 
> In linux:
> $ git grep '"label"' net/dsa/dsa2.c
> net/dsa/dsa2.c: const char *name = of_get_property(dn, "label", NULL);
> 

Hm, if Linux is using the label, then do we need to rename things in userspace?

--Sean