On Thu, Jun 27, 2013 at 12:13:55AM +0200, Arnd Bergmann wrote:
> > Sorry, I still don't get it. Are you saying that kmap_atomic is
> > available before kmap_init() (in paging_init())?
> >
> > If not, all of my mappings are discarded (well, abandoned to be more
> > correct), so I don't see how it affects kmap.
>
> Sorry, I was under the assumption that the mappings are meant to
> stay around.
Ok, just so I'm not completely lost :)
No, the purpose is just like for x86 - do early parsing of things like
the UEFI system and configuration tables, DMI and ACPI, in order to
populate global structs and stuff.
> > Indeed - almost immediately.
> >
> > x86 early_ioremap can coexist with kmap; the intent of my
> > implementation is to use the kmap region only before kmap is available.
>
> So if you never plan to use fixmap and early_ioremap at the same time,
> why even bother using the fixmap code? Wouldn't it be easier to just
> use the same memory area and ensure we never use fixmap before
> we're done with early_ioremap?
Well, I did have a crazy idea that much/most of the early_ioremap code
could be made generic and shared between x86 and arm (and any other
32-bit architecture). Using the fixmap macros would make that possible
with a minimum of ifdefs.
If we ever wanted early_ioremap() to work like on x86, beyond kmap_init()
(but not beyond the "booting" system state), using the same macros would
help there too. I had no need for that for my EFI patches.
/
Leif
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