[U-Boot-Users] crc32 checksum header in bootvars section of flash

[U-Boot-Users] crc32 checksum header in bootvars section of flash

[u-boot user]

Hello all,

Can anybody tell me where in u-boot source code and how is the crc32
checksum generated for the bootvars  
section in flash? I edited the bootvars and have saved it to a file. The
crc32 checksum header needs to be appended at the beginning of bootvars. I
need to load the bootvars file and change it according for different board
configurations. I put printf statements in env_common.c in u-boot source
code in function env_crc_update() to print the crc32 checksum it calculates.
But the values in the bootvars section in flash do not match with the printf
values? There is a crc32 command in the u-boot bootloader as well. Is that
used to calculate the checksum in the bootvars section? If yes, then what
option is it used with and can we replicate the same code in user space so
we can edit our own files and append checksums to it at the beginning?

I look forward to your replies.

Thanks and Regards
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[U-Boot-Users] crc32 checksum header in bootvars section of flash

[Wolfgang Denk]

In message <14702144.post@talk.nabble.com> you wrote:
> 
> Can anybody tell me where in u-boot source code and how is the crc32
> checksum generated for the bootvars  

This should be trivial to find in the source code, shouldn't it?

> But the values in the bootvars section in flash do not match with the printf
> values? There is a crc32 command in the u-boot bootloader as well. Is that
> used to calculate the checksum in the bootvars section? If yes, then what
> option is it used with and can we replicate the same code in user space so
> we can edit our own files and append checksums to it at the beginning?

I think what you're trying to do is  broken  by  design.  Instead  of
trying  to  rely on internal information of U-Boot (how it stores the
environment  variables)  you  should  instead   use   the   official,
documented interfaces to do what you want to do.

Instead of crafting some  binary  blob  that  holds  the  environment
variables  in  some  undocumented  internal format, you should simply
write a text file which sontains the wanted variable settings in form
of "setenv" commands, then convert  this  text  file  into  a  script
image,  and  finally  use the U-Boot "autoscr" command to apply these
settings.

Thius way you can be sure that U-Boot will compute the correct
checksum itself.

Also, you have simple text files which are much easier to maintain
than binary blobs.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
He had quite a powerful intellect, but it  was  as  powerful  like  a
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steer.                          - Terry Pratchett, _Lords and Ladies_