Re: [PATCH] MTD: fix dataflash 64-bit divisions

[David Brownell <david-b@pacbell.net>]

On Wednesday 17 December 2008, Artem Bityutskiy wrote:
> > Would this be part of a set of patches making 4 GByte
> > (and eventually, larger) NAND chips behave?
> 
> Well, this patch does only part of the job - it changes
> in-kernel API. Yes, makes >4GiB NANDs behave, and we tested
> it with NAND simulator (nandsim).

Good.  Larger parts seem to be easy to find nowadays,
and that particular limit seemed quite significant.


> However, all the user-space interfaces are still 32-bit.
> And the interfaces are not extendible, so someone should
> invent completely new MTD interfaces.
> 
> And to support 4KiB-page NANDs, which have 128bytes OOB,
> one needs to change user-space interfaces (ioctls), because
> they support 64-bit OOBs at max. On the other hand, I
> personally do not care about OOB support, because it is
> in general better to avoid any use of OOB.

This case was 2 GByte NAND chips with 4KiB pages.  The
important goal was being able to use them to hold much
filesystem data -- with 80 bytes hardware ECC data for
each 4KiB page -- and if the ioctls were also an issue,
I wouldn't have heard.

- Dave