- This variable can be used to run specific code before the normal startup (i.e. CONFIG_BOOTDELAY loop, autostart or interactive mode) begins. This is especially useful when its contents are generated automatically, i.e. by checking for keypresses, etc.
- [todo: explain update procedures using U-Boot]
- Loading Compressed Images
- Sometimes you may want to store
some data in compressed format (for example to save flash memory), while
your application needs the data in uncompressed form. You can trick U-Boot
to do this uncompressing like this:
Generate a compressed U-Boot image of type "standalone" (="mkimage ... -T standalone -C gzip ..."=) and make sure that the envrionment variable
autostartis set to
no(i. e. enter
"setenv autostart no;saveenv"). If you then use "bootm" for such an image, U-Boot will uncompress the contents of the image and store it at the "load address" (
"-a"option for mkimage), but not attempt to start it yet. If the image contains executable code, you can omit the setting of "autostart", and U-Boot will automagically start the image by jumping to the entry point address ("-e" option for mkimage).
|11. The powerful U-Boot command line interface||1. Embedded Linux Training course||12. Build, configuration of the Linux kernel, more details|