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

Ian Abbott abbotti at mev.co.uk
Thu Dec 20 22:36:39 UTC 2012


On 20/12/12 17:09, H Hartley Sweeten wrote:
> Hello all,
>
> I have a question...
>
> 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.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti at mev.co.uk>        )=-
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