Bootloader

[Felipe Balbi]

On Wed, Mar 19, 2008 at 09:33:22PM +0000, Andy Green wrote:
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> Somebody in the thread at some point said:
> 
> > I think JFFS2 is fine with just the bad block information already
> > stored in NAND, i.e., it doesn't actually need the bad block table.
> > This needs verifying, also from a performance aspect.
> 
> Well that will be simpler.
> 
> > For basic sequential read/write operations, we can skip over bad
> > blocks easily enough.
> 
> OK.
> 
> > For issue 2), I'd attack from two angles: a) reduce the number of
> > partitions and make them larger. b) don't try to have "exact" sizes
> > but just add some spare blocks (and use statistical assurances, see
> > below)
> 
> Hum.  Since we can't parse ext2 at the moment we will need at least
> these partitions if I understood the intention for NAND
> 
>  - bootloader
>  - kernel commandline string
>  - backup kernel
>  - backup rootfs
> 
> and additionally if we accept to use NAND for the main rootfs
> 
>  - main kernel
>  - main rootfs (biggest)
> 
> Burning a few MB of 256MB in padding sounds OK.
> 
> >>  - What about an environment?
> > 
> > Radical approach: hard-code anything that's environment (which would
> > be basically the boot parameter line - everything else is just the
> > partition table, internal u-boot housekeeping, or boot menu). Users
> > pick the kboot kernel if they want to pass their own parameters. (*)
> 
> I agree that if we define the bootloader as just a kernel loader, then
> the only legitimate settings in there would be directly to do with how
> to run the kernel.  But isn't it a serious problem that we need a
> different kernel image to run from SD (root=mmcblk<n>p<m>...) in that
> case than from NAND?  And then the kernels will only function when
> coming from a specific partition index on their specific media?

In the worse case, we keep u-boot for development purposes, but devices
will ship with a minimal bootloader.

-- 
Best Regards,

Felipe Balbi
me at felipebalbi.com
http://blog.felipebalbi.com