[U-Boot-Users] how to program a bootloader

[U-Boot-Users] how to program a bootloader

[Mildred Frisco]

Hi,
This might not be the exact list for this but hope some here would be
able to help me.  Is there a step-by-step guide on how to program a
bootloader?  The u-boot bootloader (or other linux bootloader) is a
very big program to study. I would like to know how to program the
basics and concepts.
Thanks.

Mildred

[U-Boot-Users] how to program a bootloader

[Shakthi Kannan]

Hi Mildred:

Mildred Frisco <mildred.frisco@gmail.com> wrote:
<quote>
Is there a step-by-step guide on how to program a
bootloader? The u-boot bootloader (or other linux
bootloader) is a
very big program to study.
</quote>
?
I think we are in the same boat :)

I was looking for a bootloader that can be
reprogrammed/extended for target ARM. U-boot allows us
to do the same, although, most of the commands have
already been implemented. Check in the doc/ directory
for README.commands file. It tells you how to add new
commands. 

I haven't written and tested any new commands yet,
but, was able to compile u-boot for the target
at91rm9200 ARM.

Regards,

K Shakthi


		
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[U-Boot-Users] how to program a bootloader

[Detlev Zundel]

Hi Mildred,

> This might not be the exact list for this but hope some here would be
> able to help me.  Is there a step-by-step guide on how to program a
> bootloader?  The u-boot bootloader (or other linux bootloader) is a
> very big program to study. I would like to know how to program the
> basics and concepts.
> Thanks.

Well look at it this way - what does a bootloader do?

- Initialize the hardware
- Setup everything so the booted program finds what it needs
- What abilities are needed to do this in a comfortable way?

Well there's your requirements ;)  Now find the relevant hardware and
software documentation to write a program doing just that.

The complexity of U-Boot is due to supporting many different
platforms.  Try studing the code relevant for _one single_ board and
you have an excellent object to study.

For a somewhat more detailed specification read the docs about the
available U-Boot commands in the DULG documentation.  Most commands
are there because they serve a purpose necessary for a comfortable
working of a bootloader.  Read the README in the toplevel directory to
read more about the "invisible parts" of U-Boot.

But remember that studying a working fully fledged boot loader can be
somewhat irritating if you just want to see clearly the basic
concepts.  On the other hand there is _nothing better_ to study than
such a Free Software project that has features needed and added by a
community much larger than most closed software development teams.

Cheers
  Detlev

-- 
"It's amazing I won. I was running against peace, prosperity, and
incumbency."
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      minister Goran Perrson, unaware that a live tv camera was still on