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

> > That would return memory that is not guaranteed to be within the first
> > 16MB of address space, so a GFP_DMA allocation would succeed with memory
> > not from ZONE_DMA.
>
> Err, no. GFP_DMA returns memory in a zone which the platform has setup.
> There's nothing specific about it being "16MB" or any other size; the
> arch can chose what size that is.
>

Sorry, was talking from the x86 perspective, which probably doesn't make
much sense since we're talking about an arm driver :)

> > That's an invalid configuration, so users, including
> > you, should at least edit their .config by hand to enable CONFIG_ZONE_DMA
> > as a workaround.
>
> Again, no. This change has caused a load of previously working drivers
> to suddenly start failing without _any_ explanation why or even warning
> about the change. It needs to start off as a WARN_ON() so that stuff
> can be fixed, and then changed to a hard error.
>

I haven't seen a "load" of error reports where this is causing an issue,
maybe it is much more popular on arm?

This also isn't a hard error, admins should be able to enable
CONFIG_ZONE_DMA and rebuild so that the driver being loaded can get the
type of memory it is requesting. Just putting a WARN_ON() doesn't provide
any incentive to ever get this stuff fixed.


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