[OE-core] using wic and extlinux together

[Trevor Woerner]

Hi Maciej,

I'm working on an OE BSP layer and was hoping you could help direct
me somewhat. Ultimately what I'd like to do is add the string " debug
earlyprintk" to the kernel cmdline (for U-Boot). The BSP I'm working on uses
wic, and has a "--source bootimg-partition" configuration in its wic file.
This invokes scripts/lib/wic/plugins/source/bootimg-partition.py.

In theory there are two ways I could reach my goal:

1) tweak scripts/lib/wic/plugins/source/bootimg-partition.py to include the
   extra options
2) generate my own extlinux.conf file

Generating my own extlinux.conf file involves defining a bunch of
UBOOT_EXTLINUX_* variables. When I do this, the extlinux.conf file is created,
but it gets ignored/clobbered by the stuff wic does. It looks like the wic
code has an option to look for an extlinux.conf file, but for some reason it's
not finding the one OE is generating. Any idea where it is looking?

	configfile = cr.ks.bootloader.configfile
	...
	    custom_cfg = get_custom_config(configfile)

In any case, there is no apparent way to tweak what wic generates. Either wic
generates its own extlinux.conf file, or it uses the one it finds (wherever it
is looking).

Would it make sense for me (or you, if you want) to tweak
scripts/lib/wic/plugins/source/bootimg-partition.py to make use of any
UBOOT_EXTLINUX_* variables it might find when generating the extlinux.conf
file?

Best regards,
	Trevor