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

Russell King
2009-01-06T23:13:46Z

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@intel.com>
Acked-by: Russell King <rmk+kernel@arm.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@gmail.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/