Ask for some guidance...

[David Woodhouse]

On Tue, 24 Jul 2001, Vipin Malik wrote:

> It's not trivial to do FTL inside some "prom's". Depending on how large 
> (rather small) they are, they may be doing just chip decoding.

lapdancer /home/dwmw2/working/mtd/drivers/mtd $ size ftl.o
   text	   data	    bss	    dec	    hex	filename
  12947	    128	   9216	  22291	   5713	ftl.o

Not too hard to put it in prom. The DiskOnChip 1000 did.

> Most of the times IDE disk's are emulated under a "special" BIOS that 
> translate the BIOS IDE int (int 13?) into read/writes of the Flash sectors.

<pedant> INT 13h is generic block device. Not IDE-specific. </pedant>

> What BIOS is it using? I know that General Software's Embedded BIOS 
> supports that functionality.

Do you know the format used?

> There is not much that you can do re. accessing this disk under Linux as 
> Linux does not use the BIOS for IDE disk access.

There are patches for the 1.1 kernel to do that :)

> Simple (!), use "Debug" under DOS, to trace into the BIOS IDE interrupt and 
> see that it does.

This works, although it tends to make my head hurt. Guess how we got 
DiskOnChip working? :)

> >         - Do you think we could access to the flash disk using MTD?
> 
> That's probably the most sensible approach in my mind- though you would not 
> access the flash _disk_, rather just the flash under MTD, which would show 
> up as a char and block device on which you could then mount JFFS2 and then 
> access it like a regular file system through Linux, including booting from it.

For booting, compatibility with the existing BIOS extension is useful. 
Until someone provides MTD and JFFS2 support for Grub, that is - I have 
Grub booting from prom (actually from DiskOnChip) quite happily.

-- 
dwmw2