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SubjectRe: IrDA driver fails on PXA255
On Sun, 29 May 2011, Russell King - ARM Linux wrote:

> We might as well enable CONFIG_ZONE_DMA for everything if that's what
> you're proposing, because it's not just this driver which will be affected.

I'd certainly suggest at least defaulting it to on for arm if you're going
to be using GFP_DMA in drivers.

> And as soon as we do that, we completely lose the warnings that stuff
> needs fixing.
>

That's because nothing needs fixing at that point, the page allocator is
guaranteed to return lowmem if GFP_DMA is passed and CONFIG_ZONE_DMA is
enabled, or NULL. Whether GFP_DMA is correct in the memory allocator is a
different subject, but those types of audits can easily be done on the
source code. In my opinion, we should be doing "select ZONE_DMA" on any
Kconfig option that builds a driver that unconditionally uses GFP_DMA.

The current behavior exists so that the admin reports the error here so it
can get fixed up (either by finding that GFP_DMA is unnecessary, selective
depending on the particular hardware, or modifying the Kconfig) and can
workaround the problem by forcing CONFIG_ZONE_DMA.


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