# Re: \[RFC/PATCH 1/3\] powerpc: add ioremap\_bat() function for setting up BAT translated IO regions.

- From: Kumar Gala \<hidden\>
- Date: 2008-08-07 18:22:23 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2008/08/9444314
- Thread: https://ratatoskr.run/linuxppc-dev/2008/08/9444193/t.md

```text

On Aug 7, 2008, at 11:45 AM, Scott Wood wrote:

> On Wed, Aug 06, 2008 at 05:11:08PM -0600, Grant Likely wrote:
>> I do this particular test to make absolute sure that the caller
>> absolutely understands the limitations of the block mapping.  If they
>> call this with something that isn't 128k aligned, then I make it fail
>> immediately so the coder is forced to go and understand what they are
>> allowed to do.  Basically, I'm reinforcing the fact that this is not
>> the same as ioremap().
>>
>> I haven't decided yet if I should test size in the same way.  Thoughts?
>
> I'd prefer it round up the size as needed to cover the requested mapping
> and needed alignment.
>
> The minimum size is going to be different on Book E, for example, and I
> can think of at least one user that will be shared between Book E and
> classic (CPM2 early console).

Which is how ioremap works today.  We ask for a size of 3 bytes and it rounds up to a 4k page.  The same should be true of the new interface (and round up to whatever the smallest size the HW we are using can handle).

- k
```