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SubjectRe: Proposal: Eliminate GFP_DMA
Martin J. Bligh wrote:
>>>>>umm. are you volunteering to convert drivers/net/macmace.c to the pci_*
>>>>>API then? also, GFP_DMA is used on, eg, s390 to get memory below 2GB and
>>>>>on ia64 to get memory below 4GB.
>>>>
>>>>The ia64 is a fine example of how broken it is. People have to hack around
>>>>with GFP_DMA meaning different things on ia64 to everything else. It needs
>>>>to die.
>>>
>>>At least on x86-64 it is still needed when you need have some hardware
>>>with address limits < 4GB (e.g. an 24bit soundcard)
>>>
>>>pci_* on K8 only allows address mask 0xffffffff or unlimited.
>>
>>That's a bit broken... I have an ALS4000 PCI soundcard that is a 24-bit
>>soundcard. pci_set_dma_mask should support 24-bits accordingly,
>>otherwise it's a bug in your platform implementation... Nobody will be
>>able to use certain properly-written drivers on your platform otherwise.
>
>
> If we're going to really sort this out, would be nice to just pass an upper
> bound for an address to __alloc_pages, instead of a simple bitmask ;-)

To do it properly, I think you'd need to give a range, not just an upper
bound. On some ARM / XScale systems, you can specify a window of your
RAM that is visible on the PCI bus. That may be a case too odd to care
about, but I'm going to have to at some point in the future....

Eli
--------------------. "If it ain't broke now,
Eli Carter \ it will be soon." -- crypto-gram
eli.carter(a)inet.com `-------------------------------------------------

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