MTD with non-power-of-2 page size

Sascha Hauer s.hauer at
Wed Aug 19 07:20:20 PDT 2015

Hi Dave,

On Wed, Aug 12, 2015 at 12:21:00PM +0100, Dave Kitchen wrote:
> I have just started to work with barebox on an Atmel at91sam9g45 processor.
> The board has an Atmel AT45DB161 dataflash configured as 528-byte page size.
> I find that eg saveenv command does not run as the page erase fails
> with EINVAL. On tracing this is fired from the page size and offset
> correction code [mtd/core,c mtd_erase_align()] which uses bit
> masking to align the size and offset. Unfortunately bit-masking does
> not work with non-power-of-2 pages. Has anyone else addressed this
> problem?
> The 'trivial' exercise of replacing the bit masks by modulo [%]
> operator does not succeed as the compiler I am using (gcc!) does not
> support long-long divmod.

You could use do_div here which returns the remainder. Also see the
mtd_div_by_eb() and mtd_mod_by_eb() functions which may be what you are
looking for.


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