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SubjectRe: More info for DSM w/r/t sunffb on 2.6.15-rc6

On Fri, 23 Dec 2005, David S. Miller wrote:
> Something like this patch below.
> Signed-off-by: David S. Miller <>
> diff --git a/drivers/video/sbuslib.c b/drivers/video/sbuslib.c
> index 646c43f..ac937da 100644
> --- a/drivers/video/sbuslib.c
> +++ b/drivers/video/sbuslib.c
> @@ -46,6 +46,9 @@ int sbusfb_mmap_helper(struct sbus_mmap_
> unsigned long off;
> int i;
> + if (!(vma->vm_flags & VM_SHARED))
> + return -EINVAL;
> +

Side note - as I explained to Nick the other week, VM_SHARED really means
"shared _writable_" mapping, so you're now disallowing a shared read-only
open too.

Which may be fine, of course. Especially if sbusfb always ends up giving a
writable pfn-mapping. But I wanted to check that that was what you meant
to do.

To test for MAP_SHARED, either do the is_cow_mapping() thing, or check
the VM_MAYSHARE bit.

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