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

[Linus Torvalds <torvalds@osdl.org>]

On Fri, 23 Dec 2005, David S. Miller wrote:
>
> Something like this patch below.
> 
> Signed-off-by: David S. Miller <davem@davemloft.net>
> 
> 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.

		Linus
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