Re: Proposal: Eliminate GFP_DMA

[Eli Carter <eli.carter@inet.com>]

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
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