Tibor Polgar wrote:
The original poster wanted a setup where the initrd was NOT part of the
kernel, which begs the question of how/where it would be put into flash so
something could load/uncompress it.
I regularly do this with compressed kernels (zImage) on PowerPC, ARM, and Alchemy MIPS processors. I attach the compressed ramdisk to the zImage, usually with "cat" and some shell scripts. The zImage uncompressor code will relocate the ramdisk (and potentially ask for additional kernel command line parameters) and will tell the kernel where the ramdisk is located. I don't have to recompile the kernel to do this, and best of all it doesn't require any special boot rom knowledge of the image. It works with all boot roms that can load a binary image into a memory location (not everyone uses RedBoot) :-) Another advantage is exactly the same image that you repeatedly test by loading over tftp or with a debugger can be written into flash memory without modification. It removes the need to actually have to write to flash to test the image that will be eventually written to flash. You just jump to the start of the image to uncompress/relocate/initialize/jump to kernel regardless of where it is located. When using ramdisks from flash, you must relocate them to RAM because the kernel thinks it can add the pages used by the compressed ramdisk into the free pool once the ramdisk is uncompressed into the file system cache. The uncompressor code I mentioned above will test the start address of the image and copy it to ram if necessary. There are a couple of things keeping me from making a patch for the MIPS kernel. This method is in conflict with the "compiled in" ramdisk method, and reserving the "bootmem" pages to ensure the kernel doesn't allocate the compressed ramdisk pages before they are freed doesn't work well compared to other architectures. I'm still running on luck with this latter problem, but I think I can fix it. I don't know yet what to do about the conflicts and assumptions made about the compiled-in ramdisk. Thanks. -- Dan
