On Sat, 30 Mar 2013 18:01:32 +0800, RS said:
>
> Now I think this will spend more time than the kernel code when executed.
Have you actually examined the generated code on several popular
architectures to see what gcc actually does?
(hint - many things can constant-folded at compile time. So if
Think you !
Oh , I was wrong . How careless I was.
I have fixed it :
#define _IOC_NRMASK (((1 << _IOC_NRBITS)-1) << _IOC_NRSHIFT) // if the
_IOC_NRBITS is 8 ,then the result is 0XFF
#define _IOC_DIR(nr)((nr & _IOC_DIRMASK) >> _IOC_DIRSHIFT) // when
decode , keep the same.
Now I th
On Sat, 30 Mar 2013, RS wrote:
> it defines in the kernel: #define _IOC_NRMASK((1 << _IOC_NRBITS)-1)
> //define ... #define _IOC_NRSHIFT0 ... #define _IOC_DIR(nr)
> (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK) //when decode
>
> why not define it like this:
> #define
it defines in the kernel: #define _IOC_NRMASK ((1 << _IOC_NRBITS)-1)
//define ... #define _IOC_NRSHIFT0 ... #define _IOC_DIR(nr)
(((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK) //when decode
why not define it like this:
#define _IOC_NRSHIFT 0
...
#define _IOC_NRMASK ((_IO
