Re: [PATCH 3/4] mtd: mchp23k256: add partitioning support

Chris Packham
2017-06-01T23:08:15Z

On 02/06/17 10:23, Brian Norris wrote:
> On Thu, Jun 01, 2017 at 09:30:07PM +0000, Chris Packham wrote:
>> On 02/06/17 06:43, Brian Norris wrote:
>>> On Wed, May 17, 2017 at 05:29:11PM +0200, Boris Brezillon wrote:
>>>> Can we fix allocate_partition() to properly handle the
>>>> master->erasesize == 0 case instead of doing that?
>>>
>>> Is everything actually ready for the eraseblock size to be 0?
>>
>> That was my initial motivation for faking it.
>
> Understood. I think it's probably better to avoid hacking drivers like
> you were about to, but I was also curious if anyone had thought through
> the implications of *not* forcing a non-zero size.
>
>>> That would
>>> seem surprising to many applications, I would think. Can you, for
>>> instance, even use UBI on such a device?
>>
>> I've tried ext2 and I believe Andrew has tried minix fs. We're talking
>> SRAM so UBI/UBIFS doesn't really provide much benefit for this use-case.
>
> Right. But that's not necessarily true for all NO_ERASE devices, so we'd
> probably want to think about that before allowing it.

Do we need a flag to indicate SRAM-like properties? I assume there is a
difference between NO_ERASE on ROM devices where there is just no way of
erasing the data. For {S,F,M}RAM there is no block erase operation but
you can overwrite data to destroy it (which is actually my use-case with
this SPI SRAM). I was tempted to set erase_size = 1 at one point which
in my mind was technically accurate but would probably upset the mtd
layer just as much as 0.