Re: OF compatible MTD platform RAM driver ?

Laurent Pinchart
2008-03-25T17:23:35Z

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On Tuesday 25 March 2008 18:02, Sergei Shtylyov wrote:
> Laurent Pinchart wrote:
>
> > > Heh, there was a whole company against mentioning "mtd" when we started
> > > working on this (of course, the first idea was to call the flash device
> > > type "mtd"). I don't think "mtd" looks good here -- I'd suggest
> > > "flash-ram" (if this is just a linearly mapped NVRAM).
>
> > I'm fine with "flash-ram" (even thought it looks a bit weird). I'll
> > prepare a patch.
>
> Yeah. I forgeot that "flash" means EEPROM. Actually, the main facts about
> the NVRAM that I'd want to be stated in the "compatible" property is that
> it's non-volatile and directly/lineraly mapped... Just "nvram" doesn't seem
> enopugh, maybe "linear-nvram" is.

Direct mapping is a hard requirement for the nvram if we want to use it with
the MTD subsystem. Regarding non-volatility nothing prevents a user from
using a volatile RAM as an MTD device, but there's little point in doing so.
Would it be acceptable for the "linear-nvram" specification not to include
volatile RAM ? ROM chips would be excluded too. Is that an issue ?

> And we can specify "device_type" of "nvram" indeed (and #size).

I suppose you meant #bytes.

What about sub-partitions support ? Nothing prevents RAM-based MTD devices
from being partioned. Would it be acceptable to reference the CFI/JEDEC flash
section in Documentation/powerpc/booting-without-of.txt in the description of
the nvram node ?

Best regards,

--
Laurent Pinchart
CSE Semaphore Belgium

Chaussée de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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