[U-Boot] strcmp UBoot command

[Michal Schulz]

Hello. let me introduce myself.

I'm low-level developer working on AROS (AROS Research Operating
System, http://www.aros.org/). Currently I'm working for Genesi
company where I'm responsible for e.g. UBoot port for the EfikaMX
Smarttop and smartbook ARM-based machines. See
http://www.genesi-usa.com/products for more details.

Working on the UBoot for EfikaMX I found out, that the minimalistic
shell is not able to compare two strings. Therefore I have added a new
uboot command, strcmp, which takes three arguments - two strings to
compare and the compare operator. The function can be used in
combination with "if" command as follows:

if strcmp foo <= bar; then .......; fi

The allowed operators are ==, !=, <, <=, >, >=. The two strings are
compared up to the length of shorter one, different size does not
count to the comparison. This feature is used in script which performs
automatic update of uboot only if there is a newer version available.
In order to do that I have defined a timestamp variable:

$(TIMESTAMP_FILE):
                @date +'#define U_BOOT_DATE "%b %d %C%y"' > $@
                @date +'#define U_BOOT_TIME "%T"' >> $@
                @date +'#define U_BOOT_TIMESTAMP "%Y%m%d%H%M%S"' >> $@

where U_BOOT_TIMESTAMP is available as environment variable
$firmware_version. Thanks to the partial comparison, I can use
following statement in my script:

if strcmp ${firmware_version} < 20101001; then .....; fi;

Here, commands will be executed if firmware timestamp is older than
October, 1st, 2010.


Could this strcmp command be useful for anyone else? If so, I would be
pleased to add it to the main uboot repository.

With best regards,
Michal Schulz.

--
Michal Schulz