Re: NAND & YAFFS

[Ross Younger <wry@ecoscentric.com>]

Hi Andrew,

> Im having trouble getting my head around partitions. 
> 
> If i understand the documentation correctly, the only thing the
> concept does it prevent a buggy filesystem or application reading data
> from a different partition than it "opened" with
> cyg_nand_get_partition(). The partition has zero affect on addressing.
> 
> Am i missing something? What else are partitions good for?

Partitions may be a bit of a misleading term for it, but it's the best I 
could come up with. It seems quite common for boards (both dev boards, and 
deployed products) to have a single NAND device or array, carved up into two 
(or more) separate filesystems. As you observe, addressing is completely 
unaffected, and this is based on my observations of other devices; I added 
in the boundary enforcement purely out of paranoia.

To take the example of the embedded Linux world, typically the primary boot 
loader uses the filesystem on the first partition (think of it as "/boot") 
to get a kernel or application image, which then uses the second (much 
larger) partition as its root filesystem. These two partitions could be the 
same filesystem, or the boot partition could be something simpler to 
simplify the boot loader.

Also, having the partition information in one place means that filesystems 
can read out their limits from it, rather than having to be configured 
separately.


Ross

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