Am 11.09.2013 12:37, schrieb Dirk Müller:
> Hi Stefan,
>
> thanks a lot for wrapping your head around it..
I'm still trying :-)
>> The script searches zImage in the second partition, which should be ext2
>> or ext4. It searches first in /boot, if this fails it tries /, so that a
>> setup with 3 partitions, first FAT, second ext2 /boot, third for rootfs
>> will also work.
>
> Right. what we usually did though is the patch the bootloader to load
> the SPL from extX, if possible, so that we can avoid the FAT
> partition.
On the raspi, there is no way around the FAT partition, since the chip
loads its bootloader ("bootcode.bin") from it. This bootcode.bin reads a
file "config.txt" from the FAT partition and applies settings in there.
Additionally, the contents of "cmdline.txt" are used for the kernel
command line.
One of these settings is
kernel=foo.xxx
which decides which "kernel" to load. Normally, a "kernel.img" is
loaded. But if we copy u-boot.bin to kernel.img (or change the config to
kernel=u-boot.bin), then U-Boot is used. U-Boot needs a patch, because
it needs to retrieve the "kernel cmdline" and later pass it on to the
linux kernel.
> Other than that I think there is a magic "use UEFI
> partition layout" flag in kiwi to create the extra fat partition..
I'll have to look into that.
>>>> * who creates boot.scr.img?
>>> It is you in the u-boot rpm build.
>
> No, actually it is uboot-image-setup.in in openSUSE:Factory:ARM JeOS
Yes, that was the information I was missing. I'll do further experiments.
I'm not even 100% sure I will go with U-Boot, since I had massive
problems with its limited (function wise) drivers. It simply could not
read one of my SD-Cards (a Transcend Class 10 16GB SDHC which works very
well once linux is booted). I might use a linux kernel as "bootloader"
and then kexec into the final kernel. This option would also allow me to
use a very sophisticated script language for the boot configuration file :-)
--
Stefan Seyfried
"If your lighter runs out of fluid or flint and stops making
fire, and you can't be bothered to figure out about lighter
fluid or flint, that is not Zippo's fault." -- bkw
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