/* linux-3.08/include/linux/const.h */

/* const.h: Macros for dealing with constants.  */

#ifndef _LINUX_CONST_H

#define _LINUX_CONST_H

/* Some constant macros are used in both assembler and

 * C code.  Therefore we cannot annotate them always with

 * 'UL' and other type specifiers unilaterally.  We

 * use the following macros to deal with this.

 *

 * Similarly, _AT() will cast an expression with a type in C, but

 * leave it unchanged in asm.

 */


/* 
 * 上边的注释说：一些常量宏同时在汇编和C中使用，然而，我们不能像注释C的常量宏那样加一个“UL”或其他后缀。所以我们需要使用以下的宏解决这个问题。
 *            例如调用：#define DEMO_MACRO _AT(1， UL)：在C中会被解释为 #define DEMO_MACRO 1UL； 而在汇编中什么都不做，就是: #define DEMO_MACRO 1
 */

#ifdef __ASSEMBLY__

#define _AC(X,Y)    X

#define _AT(T,X)    X

#else

#define __AC(X,Y)    (X##Y)

#define _AC(X,Y)    __AC(X,Y)

#define _AT(T,X)    ((T)(X))

#endif

#endif /* !(_LINUX_CONST_H) */