On 02/28/2011 06:32 AM, Somebody in the thread at some point said:
Hi -
Many powerful features can be implemented this way - install and
update scripts, booting alternative kernels, root file systems or
system configurations, enablign IP autoconfiguration using the same
network settings as already used by the boot loader, providing an
elegant method for dynamic configuration of the MTD partitions, etc.
etc.
Actually all that stuff is better done by Linux no matter how hard the
bootloader tries, I think we can agree.
Being able to provide a kernel command line in the DT (or in the
static kernel configuration) is only really useful with stupid boot
loaders that cannot pass boot arguments.
Qi builds up a kernel commandline from static and filesystem data like this:
[arch specific part]
[board specific part]
[board revision part]
[kernel source part]
[append file from kernel source part]
The first is static and decided by the arch, eg, OMAP3; the second is
decided by the board type that was probed; the third allows override by
board revision which is also probed (so you can deal with console UART
moving between revisions); the fourth part is defined by the source of
the kernel you are trying to boot, so it can set, eg,
root=/dev/mmcblk0p2 reflecting where the associated filesystem for that
kernel can be found; and the last part comes from a file in the same
filesystem as the kernel bring booted to allow arbitrary user additions.
Typically, the probing approach narrows down the correct commandline
that you don't need the user file, but if you do want to override stuff,
you can do it there.
-Andy
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