[U-Boot-Users] ROMFS & Uboot.

Wolfgang Denk wd at denx.de
Tue Jun 10 17:16:46 CEST 2003

In message <D96E2AFA0DF3D211B139009027454948034CBDF4 at helios.gnv.tcc.thomson-csf.com> you wrote:
> Well, my problem is that I am really short of ram.

Easy to fix: add more RAM. RAM is very cheap these days.

> So I would like to have my filesystem in flash and keep it in flash.
> So I would like to have my root filesytem in flash ( possible ?? ).
> romfs seems to be a way to do it.

Of course this is possible. And there  are  many  ways  to  implement
this: romfs, cramfs, jffs2, ...

> It think the way to do it it to declare my romfs as initrd ( maybe I am
> wrong because initrd is init ram disk and it means that it MUST be a RW
> filesystem in RAM ??? )

Right. An initrd is a RAM disk. And a RAM disk is in RAM by definition.

> After reading sources of U Boot it seems that if I put a second parameter at
> bootm, it is going to copy the initrd into RAM ( right ? ).

Not really. Current versions of U-Boot allow to avoid the extra  copy
of  the  ramdisk  image. But the LInux kernel will load the initrd to
RAM in any case.

> whereas I would like to keep my romfs in flash.

Then use a flash filesystem.

> maybe I misunderstand and misuse completly the initrd... Help and hints
> welcome...

Have a look at the MTD layer. You have to enable MTD support  in  the
Linux kernel. Then you can define partitions on your flash memory and
create  block  devices  on  these. And on these block devices you can
uses filesystems - whichever you like.

But all of this is actually completely unrelated to U-Boot  and  thus
off topic here.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
"What if" is a trademark of Hewlett Packard, so stop using it in your
sentences without permission, or risk being sued.

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