Re: [Buildroot] [PATCH 3/5] configs/rock5b: enable eudev to enable automatic module loading

[Niklas Cassel via buildroot <buildroot@buildroot.org>]

On Tue, Sep 03, 2024 at 09:26:11PM +0200, Thomas Petazzoni wrote:
> On Mon,  2 Sep 2024 12:44:31 +0200
> Niklas Cassel via buildroot <buildroot@buildroot.org> wrote:
> 
> > From: Niklas Cassel <cassel@kernel.org>
> > 
> > The arm64 defconfig enables both the R8169 Ethernet driver and the
> > PHY_ROCKCHIP_NANENG_COMBO_PHY PHY driver as modules.
> > 
> > Enable udev so that these modules will get automatically loaded by udev
> > after the rootfs is mounted from the SD card.
> > 
> > This way, we do not need to build these modules as built-in, and we also
> > get the benefit that any device plugged in to the PCIe slot will get
> > automatically loaded.
> > 
> > Signed-off-by: Niklas Cassel <cassel@kernel.org>
> 
> I'm not sure what we want to do here, especially when this ends up
> needing net.ifnames=0 that you add in PATCH 4/5.
> 
> We do have already a small number of defconfigs that enable eudev. So
> far we only use net.ifnames=0 in 4 configurations.
> 
> Basically, I'm trying to make sure we remain consistent and have a
> policy that applies to all defconfigs rather than ad-hoc solutions that
> are different for each and every defconfig. That's why I'm a bit
> reluctant with applying your patches as-is because they only solve the
> specific case of this defconfig, in a specific way, without creating a
> clear rule that all defconfigs meeting a specific situation should
> follow.

(Replying with the email that I have subscribed to the list this time.)


An alternative to specify net.ifnames=0 on the kernel command line
(to disable udev predictable NIC names), is to create an empty file:
/etc/udev/rules.d/80-net-name-slot.rules

See:
https://wiki.gentoo.org/wiki/Udev#Optional:_Disable_or_override_predictable_network_interface_naming

I guess we could modify package/eudev/eudev.mk and package/eudev/Config.in
to create a new BR2_PACKAGE_EUDEV_PREDICTABLE_NIC_NAMES Kconfig which we
default to "not set".

If BR2_PACKAGE_EUDEV_PREDICTABLE_NIC_NAMES is "not set", we install/touch
/etc/udev/rules.d/80-net-name-slot.rules in the target rootfs.

That would avoid the need for net.ifnames=0. We could also remove it for
the existing boards that have it set.

Any board that actually wants predictable NIC names can set the new
BR2_PACKAGE_EUDEV_PREDICTABLE_NIC_NAMES Kconfig.

Thoughts?


Kind regards,
Niklas
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