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

[Sean Anderson]

On 8/20/22 5:16 AM, Pali Rohár wrote:
> On Wednesday 10 August 2022 00:45:35 Pali Rohár wrote:
>> On Tuesday 09 August 2022 18:41:25 Sean Anderson wrote:
>>> 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?
>>
>> It uses it _only_ for DSA drivers. For all other drivers (e.g. USB or
>> PCIe based network adapters) it does not use label.
> 
> Hello Sean! I would like to ask, are you going to use/implement "label"
> support (so it would work also for non-DSA drivers) in userspace, in
> similar way how you did aliases? https://github.com/systemd/systemd/pull/24265
> 

Hi Pali,

No, I have no plans to do that.

--Sean