[Q] comedi: vmap of the async->prealloc_buf

H Hartley Sweeten hartleys at visionengravers.com
Thu Dec 20 23:38:38 UTC 2012


On Thursday, December 20, 2012 3:37 PM, Ian Abbott wrote:
> On 20/12/12 17:09, H Hartley Sweeten wrote:
>> In the comedi core, the asynchronous 'prealloc_buf' is vmap'ed after
>> the page list has been allocated. The code in question looks like this:
>>
>> 			async->prealloc_buf =
>> #ifdef PAGE_KERNEL_NOCACHE
>> 				vmap(pages, n_pages, VM_MAP, PAGE_KERNEL_NOCACHE);
>> #else
>> 				vmap(pages, n_pages, VM_MAP, PAGE_KERNEL);
>> #endif
>>
>> Is the #ifdef something left over from an older kernel?
>>
>> Isn't PAGE_KERNEL_NOCACHE always defined?
>
> Unfortunately not; it's arch dependent.  Neither ARM nor PowerPC define 
> it, for example.

Well that's annoying...

Hmph...

Hartley





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