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.
I thought we're currently talking about a driver controlling the directly
mapped NVRAM. The "compatible" property wouldn't allow us to specify the
compatibility to *any* NVRAM since there could be no "least common
denominator" driver anyway.
Regarding non-volatility nothing prevents a user from
using a volatile RAM as an MTD device, but there's little point in doing so.
Indeed, if just for testing... we could specify non-volatility as the
device's prop, though...
Would it be acceptable for the "linear-nvram" specification not to include
volatile RAM ? ROM chips would be excluded too. Is that an issue ?
Well, I think we need a separate "compatible" prop for ROMs. Or we'll end
up with the "compatible" being just "memory" with the memory "attributes"
(R/O, N/V) being described by other "properties"... :-)
And we can specify "device_type" of "nvram" indeed (and #size).
I suppose you meant #bytes.
Of course. :-)
What about sub-partitions support ? Nothing prevents RAM-based MTD devices
Hm... I remember that the knowledge of MTD partitions turned me away from
"nvram" device type when I started spec'ing the flash binding -- it's not
uncommon to have a flash partition devoted to and labelled as "nvram".
Therefore, that sole partition would have been a "nvram" device for OF...
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 ?
I don't see why not.
Best regards,
WBR, Sergei
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