Re: [PATCH net-next 3/3] net: dsa: connect a late-arriving PHY at ifup

[Aleksei Sviridkin <f@lex.la>]

> How about making the DSA driver depend on the PHY. That would be much
> simpler.

I worked through both halves of that for OpenWrt, where one kernel
image serves every board of a target, so every kilobyte lands on all of
them.

Built-in: the PHY driver itself is cheap, under 8k of text and data on
arm64. The firmware still lives on the rootfs though, and a built-in
driver probes from an initcall, before mount_root(), so blocking in
config_init() until the firmware shows up deadlocks the boot. Putting
the firmware in the kernel image costs 144k on every board of the
target, and almost none of them have this PHY.

Modules: that works, and the kernel gets smaller. OpenWrt already does
it elsewhere, kmod-dsa-mv88e6xxx depends on kmod-phy-marvell. What
stops me is that it moves the switch driver out of the kernel for every
board of the target, and NFS root goes with it. That is a bigger change
than I want to push on my own, and it gives up the case you asked
about.

Do you see a third option, or is the module direction the one you would
take, with NFS root treated as acceptable to lose on boards like these?
MODULE_SOFTDEP looks useful where dracut builds the initramfs, OpenWrt
builds its own, so I am not sure it applies here.