Re: [PATCH 2/2] Add support for > 2GiB MTD devices

[Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>]

On 27.08.2008 20:51, Jamie Lokier wrote:
> Bruce_Leonard@selinc.com wrote:
>   
>> I'm still reluctant to change size to a 64-bit value.  There's a vague 
>> recolection of early conversations on the list that there would be little 
>> acceptance for that.  And that probably has to do with the ongoing 
>> conversation about ABI changes.  What I could do to eliminate the 
>> multiplication is introduce the same concept that the NAND layer uses, 
>> shift values.  After all, erasesize should always be a power of 2, making 
>> that a power of 2 multiplication which can be done via shifts.  By 
>> changing erasesize to erasesize_shift, I'd get something like this:
>>
>> return a->num_eraseblocks == 0 ? a->size : a->num_eraseblocks << 
>> a->erasesize_shift
>>
>> How would that suit you?
>>     
>
> Are you sure it's always going to be a power of 2?
>
> What if someone targets a board with 3 chips wired to shared address
> and parallel data buses?
>
> Or if someone makes a weird chip?  Or if you can format it in
> different ways according to desired ECC level (like you can with CDs)?
>   

IIRC I saw a datasheet for such a chip (selectable erasesize with
non-power-of-2 default) some weeks ago and it had entered production a
few months ago. The erasesize was alwas a multiple of 16, though. Sorry
for not remembering more details.

Regards,
Carl-Daniel

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