Re: [PATCH 28/74] Incrementing the ecc_pos array to contain 128 char

[Brian Norris <computersforpeace@gmail.com>]

On 9/1/2010 3:21 PM, Ryan Mallon wrote:
> On 09/02/2010 09:54 AM, Kevin Cernekee wrote:
>> On Wed, Sep 1, 2010 at 2:23 PM, Ryan Mallon <ryan@bluewatersys.com> wrote:
>> http://git.infradead.org/users/dedekind/l2-mtd-2.6.git/commitdiff/b6d6ae730be2750fac166ed9df11ee6ea54d9160
> 
> That patch still breaks the ABI by renaming struct nand_ecclayout to
> nand_ecclayout_user. Any application using the old names will have to be
> rewritten to compile against a new kernel.

I don't know how exactly all user-space apps deal with this, but isn't
that what the following typedef is for? (include/mtd/mtd-user.h)
	typedef struct nand_ecclayout nand_ecclayout_t;
changed to:
	typedef struct nand_ecclayout_user nand_ecclayout_t;

So any app that properly used nand_ecclayout_t would not need changes
even when using the new headers. Again, I don't know who has been using
what in user-space.

> The old interface should remain unchanged in that include/mtd/mtd-abi.h.
> If an application using the old interface calls any of the ecc ioctls
> for a nand chip with > 64 bytes ecc it should return an error.
> 
> I still think the eccpos field should be a pointer, so that it can
> allocate as much space as is needed for the ecc. This also means that
> the kernel doesn't need to be changed every time a new NAND chips
> appears with a bigger ecc size.

Yes, dynamic allocation would probably make more sense in the future.
However, it seems difficult (or impossible?) to create an
arbitrary-sized ioctl; the size is hard-coded into the ioctl definition.

I'm curious how many applications actually need to have the ecclayout.
nandwrite doesn't actually use it, just oobinfo.