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SubjectRe: DMA API issues
James Bottomley wrote:

>On Fri, 2004-06-18 at 19:14, Ian Molton wrote:
>
>
>>On 18 Jun 2004 19:04:11 -0500
>>James Bottomley <James.Bottomley@SteelEye.com> wrote:
>>
>>
>>
>>>Because the piece of memory you wish to access is bus remote.
>>>
>>>
>>No, its *not*
>>
>>my CPU can write there directly.
>>
>>no strings attached.
>>
>>the DMA API just only understands how to map from RAM, not anything
>>else.
>>
>>
>
>I think you'll actually find that it is. OHCI is a device (representing
>a USB hub), it's attached to the system by some interface that
>constitutes a bus (the bus interface transforming the CPU access cycles
>to device access cycles, translating interrupts etc.).
>
>
>
Bus remote is a red herring in this case. The only difference between
this case and the ones supported by the coherent_dma_mask is that the
constraint on placement of the allocated memory cannot be encoded as a
bitmask.

Jamey

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