[RFC V6 2/3] arm:add bitrev.h file to support rbit instruction

-----Original Message-----
From: Russell King - ARM Linux [mailto:linux at arm.linux.org.uk]
Sent: Thursday, January 15, 2015 12:38 AM
To: Wang, Yalin
Cc: 'Ard Biesheuvel'; 'Will Deacon'; 'linux-kernel at vger.kernel.org';
'akinobu.mita at gmail.com'; 'linux-mm at kvack.org'; 'Joe Perches'; 'linux-arm-
kernel at lists.infradead.org'
Subject: Re: [RFC V6 2/3] arm:add bitrev.h file to support rbit instruction

On Fri, Jan 09, 2015 at 08:40:56PM +0800, Wang, Yalin wrote:

quoted

Oh, I see,
How about change like this:
+	select HAVE_ARCH_BITREVERSE if ((CPU_V7M || CPU_V7) && !CPU_V6 &&
+!CPU_V6K)
I am not sure if I also need add some older CPU types like !CPU_ARM9TDMI

&&?!CPU_ARM940T ?

quoted

Another solution is:
+	select HAVE_ARCH_BITREVERSE if ((CPU_32V7M || CPU_32V7) && !CPU_32V6
+&& !CPU_32V5 && !CPU_32V4 && !CPU_32V4T && !CPU_32V3)

By the way, I am not clear about the difference between CPU_V6 and
CPU_V6K, could you tell me? :)

I think

	select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6

is sufficient - we don't support mixing pre-v6 and v6+ CPU architectures
into a single kernel.

Ok, I will re-send a patch. 

Thanks