[U-Boot-Users] Special u-boot format for Kernels
wd at denx.de
Wed Nov 13 20:28:49 CET 2002
in message <200211131007.24226.h.schurig at mn-logistik.de> you wrote:
> For booting a Linux zImage, you simply jump to it's location (after setting up
> the registers). And you have to set up registers and jump to some extracted
> code anyway, no matter if you if the zImage is already there or if it just
> got extracted out of some mkimage-made image. Setting up the rigth registers
> with the right info is OS dependend anyway.
> What is the reason for this, why do you think the image approach is better ---
> or even necessary?
This approach is the result of recurring customer requirements. Our
* How can I identify an image I have stored in flash? Which version
is it? ==> Approach: Name String
* How can I find out when the image was built? ==> Approach: Time
* How can I make sure an image is OK, i. e. that it was neither
corrupted during download or by erasing / overwriting parts of the
flash where I stroed it? ==> Approach: CRC32 checksum
* How can I make sure I don't try booting a valid image, which is in
fact not a Linux kernel but something else (ramdisk, xxxOS image,
...)? ==> Approach: Tags for OS, type, architecture, etc.
All these issues are required byu many embedded projects where
reliability, software updates etc. play a role. That's why we wrap
the images (Linux kernel, ramdisk, multi-file images, scripts,
firmware, ...) with a special header containing all the required
metadata and checksums.
> Don't read this as a critique, I really don't understand the motivation behind
There is no technical need for the header if all you want to do is
booting a Linux kernel. But if you have to organize production of
sortware and hardware and set up all the processes for software
updates you will appreciate such mechanisms.
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
See us @ electronica 2002 in Munich, Nov 12-15, Hall A3, Booth A3.325
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