Re: can device drivers return non-ram via vm_ops->nopage?
From: Russell King (rmk+lkml_at_arm.linux.org.uk)
Date: 03/22/04
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Date: Mon, 22 Mar 2004 00:20:41 +0000 To: Jeff Garzik <jgarzik@pobox.com>
On Sun, Mar 21, 2004 at 07:10:53PM -0500, Jeff Garzik wrote:
> For the first kind, please read fb_mmap in drivers/video/fbmem.c. Look
> at the _horror_ of ifdefs in exporting the framebuffer. And that horror
> is what's often needed when letting userspace mmap(2) PCI memory IO regions.
Most of this:
#if defined(__mc68000__)
...
#elif defined(__mips__)
pgprot_val(vma->vm_page_prot) &= ~_CACHE_MASK;
pgprot_val(vma->vm_page_prot) |= _CACHE_UNCACHED;
#elif defined(__sh__)
pgprot_val(vma->vm_page_prot) &= ~_PAGE_CACHABLE;
#elif defined(__hppa__)
pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE;
#elif defined(__ia64__) || defined(__arm__)
vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
#else
#warning What do we have to do here??
#endif
exists because architectures haven't defined their private
pgprot_writecombine() implementations, preferring instead to add
to the preprocessor junk instead.
-- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/ 2.6 Serial core - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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