Re: [PATCH] radeon: Do not directly dereference pointers to BIOS area.

From: Alex Deucher
Date: Fri Mar 20 2015 - 09:50:21 EST

On Fri, Mar 20, 2015 at 5:38 AM, Christian KÃnig
<christian.koenig@xxxxxxx> wrote:
> On 19.03.2015 17:29, David Miller wrote:
>> From: Christian KÃnig <christian.koenig@xxxxxxx>
>> Date: Thu, 19 Mar 2015 09:50:58 +0100
>>> In general I would say yes, but for this particular hardware it's a
>>> bit questionable to do so.
>>> For radeon hardware to work correctly the CPU access to the PCIE BARs
>>> should work even without using the specialized IO macros/functions,
>>> otherwise mapping VRAM CPU accessible isn't really possible.
>>> What's the background of the change? Some problems on a certain CPU
>>> platform? or just general cleanups?
>> It's an _iomem_ pointer, it's not a virtual address.
>> Therefore it is illegal to dereference the pointer.
>> The value is opaque and has values that only make sense when used
>> with the readb() et al. interfaces.
>> This code is relying upon the fact that on x86 it happens to be
>> a virtual address, but this won't work on many other architectures.
> In this case I'm perfectly fine with it and the patch is Reviewed-by:
> Christian KÃnig <christian.koenig@xxxxxxx>
> Just wanted to make sure that you're not trying to get Radeon working on a
> platform which will never really support the necessary hardware features.

Applied to my tree. Thanks!

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