Re: Re: RomFS

Re: Re: RomFS

[Ruedi.Hofer]

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> Hi

Hi!

> That sounds good and it works. snip
>
> But how can I mount this rom/ramdisk from the kernel as its root disk?

Well, um, you can't.
I guess you have to write a simple read-only block device driver yourself...
I think i've seen a posting before by a guy alex@signum.se who has written
a flash file system, you might be able to steal some code from him.
Search the linuxppc-dev and linuxppc-embedded lists.

> What do I have to supply as boot parameter?
>
> I would like to store the entire application in the flash (kernel + application)

If you have enough ram, make an initrd and load with 8xxrom (I don't remember
the command, but i've done it.)

But be sure to check/fix the ramdisk, it might be broken.

I don't know your budget, but small ATA-Flash cards are cheap.
And really nice.

I've got a almost-working pcmcia driver waiting to be bugchecked
and released here...

And 8xxrom boots from ATA-Flash too.

Cheers /

Magnus

> \Ruedi
>
> damm@kieraypc01.p.y.ki.era.ericsson.se on 31.01.2000 16:23:22
> An: Ruedi.Hofer@ascom.ch @ MailGate
> Kopie:
> Thema: Re: RomFS
>
> > Hi,
>
> Hi!
>
> > My ADS board is happily running with a NFS mounted linux box.
>
> Great!
>
> > Now I have to put all the code into the flash memory to get a standalone
> > solution.
> >
> > I'm using the 8xxrom Bootloader. In a file called config.h I can configure
> > CONFIG_DISK_ROM.  As far as I can see, the bootloader assumes
> > then that a complete FAT filesystem is stored from the position
> > 0xFE020000 in flash.
> >
> > My question:
> > - Is my assumption right?
>
> Well, there is a file in the disk directory called rom.c.
> It is a simple read-only block driver for 8xxrom.
> It does not know anything about filesystems, so you can use any filesystem you want
> as long it is supported by 8xxrom.
>
> In rom.h can you find a define called ROM_DISKSTART which is the start address
> of the filesystem.
>
> > - How can I produce a FAT filesystem in a file, which I can download
> >   with MPC8BUG into the onboard flash?
>
> You have to look somewhere on the net.
> I usually create a ramdisk and make a filesystem and copy my things to it.
> Then I umount it and use dd to copy the data to a file which I burn to
> a flash.
>
> > - Does it have anything in common with the romfs driver which is supported
> >   by the kernel? (I think not)
>
> Nope.
> But it would sure be great if we could read one romfs image from the 8xxrom.
>
> Good luck /
>
> magnus

Re: RomFS

[Wolfgang Denk]

In message <0FP80082UOL8BN@pmdf-it.hasler.ascom.ch> you write:
>
> I think i've seen a posting before by a guy alex@signum.se who has written
> a flash file system, you might be able to steal some code from him.
> Search the linuxppc-dev and linuxppc-embedded lists.

Right, but he told me that he does not  maintain  this  code,  and  I
found  several  problems  with it. I fixed those for the systems I am
using (TQM8xxL modules). I  have  both  character  device  and  block
device  drivers  for  the FLASH memory on these systems. It works for
me, YMMV.

If my time permits I am willing to help if anybody is going  to  test
this  code  on  other  systems  as well - it will need a bit of work,
though.

You can find my current code as oatch  against  the  original  2.2.13
kernel  in  the  files  FLASH.patch  (for  the  character device) and
FTL.patch (for the block device) which are included in
ftp://ftp.denx.de/pub/LinuxPPC/usr/src/CDK.tar.gz

Not however, that this block device driver  re-uses  the  FTL  (Flash
Translation Layer) code from the PC-Card (PCMCIA) implementation. You
can  use  the charatcer device driver to put a new raw file (with any
filesystem image you like in it) into FLASH memory, but the FTL  code
is  probably  too difficult to include into 8xxrom - and you need it,
since it uses specal formatting of the erase  regions  used  for  the
block device.

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
Contrary to popular belief, thinking does not cause brain damage.

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