# \[RFC V6 3/3\] arm64:add bitrev.h file to support rbit instruction

- From: Will Deacon \<hidden\>
- Date: 2014-10-31 10:43:13 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2014/10/4363789
- Thread: https://ratatoskr.run/linux-mm/2014/10/4357965/t.md

```text
On Fri, Oct 31, 2014 at 05:41:48AM +0000, Wang, Yalin wrote:
> This patch add bitrev.h file to support rbit instruction,
> so that we can do bitrev operation by hardware.
> Signed-off-by: Yalin Wang <redacted>
> ---
>  arch/arm64/Kconfig              |  1 +
>  arch/arm64/include/asm/bitrev.h | 21 +++++++++++++++++++++
>  2 files changed, 22 insertions(+)
>  create mode 100644 arch/arm64/include/asm/bitrev.h
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 9532f8d..b1ec1dd 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -35,6 +35,7 @@ config ARM64
>  	select HANDLE_DOMAIN_IRQ
>  	select HARDIRQS_SW_RESEND
>  	select HAVE_ARCH_AUDITSYSCALL
> +	select HAVE_ARCH_BITREVERSE
>  	select HAVE_ARCH_JUMP_LABEL
>  	select HAVE_ARCH_KGDB
>  	select HAVE_ARCH_TRACEHOOK
> diff --git a/arch/arm64/include/asm/bitrev.h b/arch/arm64/include/asm/bitrev.h
> new file mode 100644
> index 0000000..706a209
> --- /dev/null
> +++ b/arch/arm64/include/asm/bitrev.h
> @@ -0,0 +1,21 @@
> +#ifndef __ASM_ARM64_BITREV_H
> +#define __ASM_ARM64_BITREV_H

Really minor nit, but we don't tend to include 'ARM64' in our header guards,
so this should just be __ASM_BITREV_H.

With that change,

  Acked-by: Will Deacon [ref]

Will
```