Subject: Re: MTD devices in NetBSD
To: Garrett D'Amore <email@example.com>
From: Jachym Holecek <firstname.lastname@example.org>
Date: 03/23/2006 22:05:21
> >> I've been thinking about this as well. I think this idea implies that
> >> the "block" size of these things would match that native sector size.
> > Yes & no. We can look at how cd9660 handles this, as it has the same
> > issue (2k sectors != 512 byte sectors).
> Thanks for the reference. But of course, 2k/512 is a *lot* different
> ratio than 64k/512. Especially since the media size for cd9660 is
> usually hundreds of MB, and for flash it is likely to be ~10MB.
Expect much greater capacity for NAND chips (Micron is selling upto 8Gb
parts, for instance).
> >> Hence, I think 1:1 block/sector mapping is a poor (even unworkable) choice.
> > Can you read less than a block in these things?
> For NOR, absolutely. Many NOR systems are actually mapped *directly*
> into system memory. I presume this to be true (that you can read less
> than a sector, not the mapping bit) for NAND, but I confess I'm still
> largely ignorant of NAND.
You can read/write in units of pages but you can only erase in units
of blocks (N * pages).