Re: [PATCH v3 1/3] dt-bindings: net: add Realtek r8169 family PCIe Ethernet

[Ricardo Pardini <ricardo@pardini.net>]

On 06/06/2026 22:50, Heiner Kallweit wrote:
> On 06.06.2026 07:03, Ricardo Pardini wrote:
>> On 05/06/2026 17:48, Heiner Kallweit wrote:
>>> On 05.06.2026 13:49, Ricardo Pardini via B4 Relay wrote:
>>>> From: Ricardo Pardini <ricardo@pardini.net>
>>>>
>>>> Add a binding for fixed/soldered Realtek PCIe Ethernet controllers
>>>> driven by the r8169 driver (RTL8125/8126/8127/8168 and variants).
>>>>
>>>> The "pciVVVV,DDDD" compatibles are the Open Firmware PCI Bus Binding
>>>> spelling, auto-derived from PCI-SIG vendor/device IDs, but they still
>>>> need a binding when used in a board DT - analogous to "usbVVVV,PPPP"
>>>> compatibles documented in their own bindings (e.g. microchip,lan95xx)
>>>> so board DTs attaching properties (fixed MAC, nvmem cell, ...) to
>>>> these PCI function nodes can be validated.
>>>
>>> The of node seems to be created by of_pci_make_dev_node(). But this
>>> function is called for bridges only in pci_bus_add_device().
>>> So where is the node created in your case? Did you test node creation?
>>
>> Seems to me of_pci_make_dev_node() is not at play here - that's the DT-synthesis path. For nodes already present in DT, the of_node is bound earlier, during pci_setup_device() -> pci_set_of_node() -> of_pci_find_child_device() via the 5-cell reg.
>>
> I see, thanks. If the matching is done based on the reg property, then I just wonder
> if and where the compatible string is used. Or would the logic also work with a
> random compatible string?

Thanks, Heiner. It seems the compatible is not involved in the kernel 
runtime matching at all (and u-boot simply patches DT via the ethernetN 
alias).

I guess DT-wise, specifying compatible (although not strictly required) 
makes sense since DT describes the hardware; "there's an RTL8125 at 
0x410000" sounds better than "there's a PCIe device that needs a MAC 
address at 0x410000", and having the binding opens up usages of 
non-generic properties, although that would be future-looking.

At this stage I've to ask the devicetree folks: should I simply drop the 
compatible from the DT patches (and the whole binding)? dtbs_check 
passes without it, and it also avoids the checkpatch.pl 
vendor-prefix-undocumented warning. There's precedent: at least on some 
Apple Silicon (2022, t600x-j375) and NVIDIA (2019, tegra210-p3450-0000). 
On Rockchip there's quite a few (10?) boards using the same RTL chip we 
might want to describe.

> [...]
>>> This list reflects just some of the PCI id's handled by r8169.
>>> Any specific reason for this exact selection?
>> I went for "chips likely to be soldered down on an SBC", but that was indeed speculative.
>>
>> I guess I should trim to pci10ec,8125, which is all this series describes? (further IDs can be added by the patches that introduce boards using them)
>>
> Yes, I'd prefer this approach. Considering that RTL8168 has been supported for
> about 20yrs now, your use case seems to be exotic. Otherwise I would have
> such a patch much earlier.
The Tegra Jetson Nano has an RTL8111 described in DT for this exact use 
case (without compatible) for about 7 years now -- I just couldn't find 
it until now.

I'll wait for people to chime in, and later send a v4 either dropping 
the binding, or trimming it to only the 8125. Sashiko seems to have nice 
suggestions [1] on the YAML too, in case we decide to keep the binding.

--
Regards,
Ricardo

[1] 
https://sashiko.dev/#/patchset/20260605-rk3588-dts-rtl-eth-describe-dt-alias-v3-0-8a8857b39daf%40pardini.net