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SubjectRe: [patch 2.6.26-mmotm] rtc: BCD codeshrink
On Tue, 1 Jul 2008 23:41:01 -0700 David Brownell <david-b@pacbell.net> wrote:

> This updates <linux/bcd.h> to define the key routines as constant
> functions, which the macros will then call. Newer code can now
> call bcd2bin() instead of SCREAMING BCD2BIN() TO THE FOUR WINDS.
>
> This lets each driver shrink their codespace by using N function
> calls to a single (global) copy of those routines, instead of N
> inlined copies of these functions per driver.
>
> These routines aren't used in speed-critical code. Almost all
> callers are in the RTC framework. Typical per-driver savings is
> near 300 bytes.
>
> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
> Acked-by: Adrian Bunk <bunk@kernel.org>
> ---
> include/linux/bcd.h | 9 +++++++--
> lib/Makefile | 2 +-
> lib/bcd.c | 14 ++++++++++++++
> 3 files changed, 22 insertions(+), 3 deletions(-)
>
> --- a/include/linux/bcd.h 2008-06-30 16:44:26.000000000 -0700
> +++ b/include/linux/bcd.h 2008-06-30 21:38:24.000000000 -0700
> @@ -10,8 +10,13 @@
> #ifndef _BCD_H
> #define _BCD_H
>
> -#define BCD2BIN(val) (((val) & 0x0f) + ((val)>>4)*10)
> -#define BIN2BCD(val) ((((val)/10)<<4) + (val)%10)
> +#include <linux/compiler.h>
> +
> +unsigned bcd2bin(unsigned char val) __attribute_const__;
> +unsigned char bin2bcd(unsigned val) __attribute_const__;
> +
> +#define BCD2BIN(val) bcd2bin(val)
> +#define BIN2BCD(val) bin2bcd(val)

It'd be good to nuke these things now.

Unfortunately you didn't cc the list where nukers lurk. Please do cc
linux-kernel on kernel-wide patches.

> /* backwards compat */
> #define BCD_TO_BIN(val) ((val)=BCD2BIN(val))
> --- a/lib/Makefile 2008-06-30 16:44:26.000000000 -0700
> +++ b/lib/Makefile 2008-06-30 21:38:24.000000000 -0700
> @@ -13,7 +13,7 @@ lib-$(CONFIG_SMP) += cpumask.o
>
> lib-y += kobject.o kref.o klist.o
>
> -obj-y += div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
> +obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
> bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o
>
> ifeq ($(CONFIG_DEBUG_KOBJECT),y)
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ b/lib/bcd.c 2008-06-30 21:38:24.000000000 -0700
> @@ -0,0 +1,14 @@
> +#include <linux/bcd.h>
> +#include <linux/module.h>
> +
> +unsigned bcd2bin(unsigned char val)
> +{
> + return (val & 0x0f) + (val >> 4) * 10;
> +}
> +EXPORT_SYMBOL(bcd2bin);
> +
> +unsigned char bin2bcd(unsigned val)
> +{
> + return ((val / 10) << 4) + val % 10;
> +}
> +EXPORT_SYMBOL(bin2bcd);


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