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Subject: Re: HugeTLB vs. SH3 cpu
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>,
       Nish Aravamudan <nish.aravamudan@gmail.com>,
       Adrian Bunk <bunk@kernel.org>, wli@holomorphy.com,
       linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org
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Date: Wed, 02 Apr 2008 17:06:09 -0700
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On Wed, 2008-04-02 at 15:55 -0700, Nishanth Aravamudan wrote:
> On 02.04.2008 [17:04:48 +0900], Paul Mundt wrote:
> > On Tue, Apr 01, 2008 at 04:26:14PM -0700, Nish Aravamudan wrote:
> > Sorting out the mess noted by Adrian is pretty trivial with a
> > HAVE_HUGETLB_PAGE. How about this?
> 
> I'm confused, isn't the following simpler fix equivalent?
> 
> Fix sh3 build with HUGETLBFS=y. Only SH4 and SH5 actually support
> HUGETLB_PAGE (which HUGETLBFS depends on).
> 
> Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index d731282..1981f8e 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -978,7 +978,7 @@ config TMPFS_POSIX_ACL
>  
>  config HUGETLBFS
>  	bool "HugeTLB file system support"
> -	depends on X86 || IA64 || PPC64 || SPARC64 || (SUPERH && MMU) || BROKEN
> +	depends on X86 || IA64 || PPC64 || SPARC64 || ((CPU_SH4 || CPU_SH5) && MMU) || BROKEN

Yeah, that's equivalent.  But, you have to draw the line at some point
on how complex that "depends on" is going to get.  I think you each have
unique pain tolerances. :)

Personally, I kinda prefer to break it out per-arch, because that SUPERH
logic is getting a bit screwy.

You could also do something like this:

>  config HUGETLBFS
>  	bool "HugeTLB file system support"
> -	depends on X86 || IA64 || PPC64 || SPARC64 || (SUPERH && MMU) || BROKEN
> +	depends on X86 || IA64 || PPC64 || SPARC64 || SUPERH_HUGETLBFS || BROKEN

And then:

config SUPERH_HUGETLBFS
	def_bool y
	depends on (CPU_SH4 || CPU_SH5) && MMU

on the arch-specific side.  

-- Dave