some question about / adding commandline files from rootfs

[Werner Almesberger]

xiangfu wrote:
> how about let qi read a file like qi.conf in SD card first
> partition.(this file must in first partition)

Hmm, let's see what this could do. First the good features:

- it would give the command line(s) a place to live

- (kernel) file names no longer have to be hard-coded, e.g., one
  could make a kernel called "uImage-20080827", and point to it.
  This is a bit nicer than symlinks. (But see below for the downside.)

- it would provide a means for the user to alternate between kernels
  on the secondary partition (my list of primary/secondary choices
  and fallbacks couldn't do that)

- it would give more freedom for choosing which partition is second,
  e.g., it could be the third partition instead of the second one

- it would remove policy (i.e., the sequence of things to try) from
  qi

The not so good things:

- more complex failure mode, i.e., if qi.conf cannot be found or
  is syntactically incorrect, what would qi do ? What if a file
  listed in qi.conf doesn't exist ?

- there has to be a (small) configuration file parser

- it would create a shared configuration resource, i.e., first
  and second partition would share the same file, even though
  they are otherwise independent from each other. (LILO and GRUB
  have that issue as well and nobody seems to be overly bothered
  by it, so perhaps this isn't such a big problem.)

I would be mainly worried about the larger number of failure modes
and their complexity, particularly if qi tried to be smart about it.
I like the aspect of removing policy (= frozen configuration) from
qi.

- Werner