On Thu, Dec 20, 2012 at 10:36:39PM +0000, Ian Abbott wrote: > 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. Power PC has _PAGE_NO_CACHE and the DRM subsystem uses that like PAGE_KERNEL_NOCACHE. For example PAGE_AGP is define in one of these ways: #define PAGE_AGP PAGE_KERNEL_NOCACHE #define PAGE_AGP __pgprot(_PAGE_KERNEL | _PAGE_NO_CACHE) <- only on powerpc #define PAGE_AGP PAGE_KERNEL I don't really know what's going on here though... comedia and AGP are the only drivers which use PAGE_KERNEL_NOCACHE. regards, dan carpenter _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
