linux-kernel - Re: [PATCH 14/23] arm: introduce asm/swab.h

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Date:	Tue, 6 Jan 2009 23:12:35 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Harvey Harrison <harvey.harrison@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/23] arm: introduce asm/swab.h

Thanks for bypassing me.

We've had this patch in the kernel before, then it got reverted.

Application: ae82cbfc8beaa69007aa09966d3983ac938c3577
Reversion: b35de672e74ceea6482b4f690ad053aec8465c5d

    Revert "[ARM] use the new byteorder headers"
    
    This reverts commit ae82cbfc8beaa69007aa09966d3983ac938c3577. It
    needs the new byteorder headers to be exported to userspace, and
    they aren't yet -- and probably shouldn't be, at this point in the
    2.6.27 release cycle (or ever, for that matter).
    
    Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
    Acked-by: Russell King <rmk+kernel@....linux.org.uk>

Please explain what's changed to make this acceptable now.

On Tue, Jan 06, 2009 at 01:30:52PM -0800, Harvey Harrison wrote:
> Convert to the new-style arch overrides as well.
> 
> Signed-off-by: Harvey Harrison <harvey.harrison@...il.com>
> ---
>  arch/arm/include/asm/Kbuild      |    1 +
>  arch/arm/include/asm/byteorder.h |   33 +------------------------
>  arch/arm/include/asm/swab.h      |   50 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 52 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/arm/include/asm/Kbuild b/arch/arm/include/asm/Kbuild
> index 73237bd..43b0b2b 100644
> --- a/arch/arm/include/asm/Kbuild
> +++ b/arch/arm/include/asm/Kbuild
> @@ -1,3 +1,4 @@
>  include include/asm-generic/Kbuild.asm
>  
>  unifdef-y += hwcap.h
> +unifdef-y += swab.h
> diff --git a/arch/arm/include/asm/byteorder.h b/arch/arm/include/asm/byteorder.h
> index 4fbfb22..c02b6fc 100644
> --- a/arch/arm/include/asm/byteorder.h
> +++ b/arch/arm/include/asm/byteorder.h
> @@ -15,38 +15,7 @@
>  #ifndef __ASM_ARM_BYTEORDER_H
>  #define __ASM_ARM_BYTEORDER_H
>  
> -#include <linux/compiler.h>
> -#include <asm/types.h>
> -
> -static inline __attribute_const__ __u32 ___arch__swab32(__u32 x)
> -{
> -	__u32 t;
> -
> -#ifndef __thumb__
> -	if (!__builtin_constant_p(x)) {
> -		/*
> -		 * The compiler needs a bit of a hint here to always do the
> -		 * right thing and not screw it up to different degrees
> -		 * depending on the gcc version.
> -		 */
> -		asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
> -	} else
> -#endif
> -		t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
> -
> -	x = (x << 24) | (x >> 8);		/* mov r0,r0,ror #8      */
> -	t &= ~0x00FF0000;			/* bic r1,r1,#0x00FF0000 */
> -	x ^= (t >> 8);				/* eor r0,r0,r1,lsr #8   */
> -
> -	return x;
> -}
> -
> -#define __arch__swab32(x) ___arch__swab32(x)
> -
> -#if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
> -#  define __BYTEORDER_HAS_U64__
> -#  define __SWAB_64_THRU_32__
> -#endif
> +#include <asm/swab.h>
>  
>  #ifdef __ARMEB__
>  #include <linux/byteorder/big_endian.h>
> diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h
> new file mode 100644
> index 0000000..27a689b
> --- /dev/null
> +++ b/arch/arm/include/asm/swab.h
> @@ -0,0 +1,50 @@
> +/*
> + *  arch/arm/include/asm/byteorder.h
> + *
> + * ARM Endian-ness.  In little endian mode, the data bus is connected such
> + * that byte accesses appear as:
> + *  0 = d0...d7, 1 = d8...d15, 2 = d16...d23, 3 = d24...d31
> + * and word accesses (data or instruction) appear as:
> + *  d0...d31
> + *
> + * When in big endian mode, byte accesses appear as:
> + *  0 = d24...d31, 1 = d16...d23, 2 = d8...d15, 3 = d0...d7
> + * and word accesses (data or instruction) appear as:
> + *  d0...d31
> + */
> +#ifndef __ASM_ARM_SWAB_H
> +#define __ASM_ARM_SWAB_H
> +
> +#include <linux/compiler.h>
> +#include <asm/types.h>
> +
> +#if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
> +#  define __SWAB_64_THRU_32__
> +#endif
> +
> +static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
> +{
> +	__u32 t;
> +
> +#ifndef __thumb__
> +	if (!__builtin_constant_p(x)) {
> +		/*
> +		 * The compiler needs a bit of a hint here to always do the
> +		 * right thing and not screw it up to different degrees
> +		 * depending on the gcc version.
> +		 */
> +		asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
> +	} else
> +#endif
> +		t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
> +
> +	x = (x << 24) | (x >> 8);		/* mov r0,r0,ror #8      */
> +	t &= ~0x00FF0000;			/* bic r1,r1,#0x00FF0000 */
> +	x ^= (t >> 8);				/* eor r0,r0,r1,lsr #8   */
> +
> +	return x;
> +}
> +#define __arch_swab32 __arch_swab32
> +
> +#endif
> +
> -- 
> 1.6.1.94.g9388
> 
> 

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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