Re: OF compatible MTD platform RAM driver ?

[Laurent Pinchart <laurentp@cse-semaphore.com>]

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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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