linux-kernel - Re: [PATCH] UIO: only call pgprot

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Message-ID: <8bd0f97a0811050943n79a4ced9u23fc5ae6540d458@mail.gmail.com>
Date:	Wed, 5 Nov 2008 12:43:31 -0500
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	"Greg KH" <gregkh@...e.de>, "Mike Frysinger" <vapier@...too.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] UIO: only call pgprot_noncached if defined

On Wed, Nov 5, 2008 at 12:08, Hans J. Koch wrote:
> On Wed, Nov 05, 2008 at 08:33:34AM -0800, Greg KH wrote:
>> On Wed, Nov 05, 2008 at 12:36:11PM +0100, Hans J. Koch wrote:
>> > There seem to be archs that cannot easily implement a sensible
>> > pgprot_noncached() function, so we should merge this patch. UIO doesn't
>> > compile on these archs right now.
>>
>> No, we should fix those arches to have that function at least NULLed
>> out.  Isn't there only one, Blackfin?  Putting #ifdefs in .c files is
>> not something we really want to do if at all possible.
>
> Yep, 5 minutes after I sent the mail I regretted it. Blackfin could
> easily implement an "empty" macro that just returns its parameter.

just because it's easy to do doesnt mean it's correct.  i'm looking
for the correct answer here, not the quick & dirty & forget about it.

perhaps uio_mmap_physical() should look like:
static int uio_mmap_physical(struct vm_area_struct *vma)
{
#ifdef pgprot_noncached
    struct uio_device *idev = vma->vm_private_data;
    int mi = uio_find_mem_index(vma);
    if (mi < 0)
        return -EINVAL;

    vma->vm_flags |= VM_IO | VM_RESERVED;

    vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

    return remap_pfn_range(vma,
                   vma->vm_start,
                   idev->info->mem[mi].addr >> PAGE_SHIFT,
                   vma->vm_end - vma->vm_start,
                   vma->vm_page_prot);
#else
    return -EFAULT;
#endif
}
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