In message 11273166.post@talk.nabble.com you wrote:
Let me elaborate a bit: We're thinking of having a kind of a "Disk on key" device as our primary non volatile storage. The Linux software image will be on this device, so we'll need to boot from it as well. As this is an MPC85xx based board, having no embedded USB controller, we'll also need an external PCI to USB 2.0 host controller. Writing may be needed as in our current boot process the boot application writes some temporary files on the HD (and it's also needed at development stage, when there is no image on the disk).
It is not needed. Boot Linux over Ethernet, and use the running Linux system to write the files.
I basically would like to know how painful it is to have all this ticking with the current u-boot support.
It *is* painful, as you would have to add write support both to the USB drivers (including re-testing on a lot of boards) *plus* to the file system drivers (including re-testing on a lot of boards).
It's simply not worth the effort. U-Boot is a boot loader, and if you need the services of a typical OS (like full file system support) then you should just boot an OS - that's what U-Bootis really good in.
Best regards,
Wolfgang Denk