On 2015-05-30 19:16, Gordan Bobic wrote:
This never bit me before, but since there was a question about it here
recently, I thought I'd mention it.
Due to systemd, EL7 _may_ require a kernel with the option
CONFIG_FW_LOADER=y
udev used to be able to use a userspace firmware loader helper to load
a firmware for the driver to use. Udev has since been sucked into
systemd, and the feature to use a helper has been dropped and now the
kernel is expected to handle the whole process on it's own.
That means that if you have hardware that requires a firmware blob
(typical example would be a WiFi module), it will stop working when
you upgrade to systemd if your kernel doesn't have the above feature
built in.
Finally figured this out on the Chromebook. The only fully working
kernel version for the Samsung Chromebook is the heavily patched
ChromeOS 3.4.0 kernel. Unfortunately, it looks like the kernel firmware
loading without userspace assistance only seems to work properly from
around 3.9 onward.
But there is a backup plan if you have the kernel source - you can build
the firmware blobs into the kernel. That's how I finally got WiFi
working on the Chromebook with EL7. There may be a way to alter a
pre-existing binary kernel blob (in case no usable source code is
available - gross violation of GPL, but it does happen), but I have not
looked into that (and I hope I won't have to).
Either way, it may have eaten my whole day, but I got it working in the
end. And I guess the clue factor on the subject of systemd, kernel and
firmware requirement obscurities has increased somewhat.
Gordan
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