[KJ][RFC]NAME_OFFSET macro

[Milind Arun Choudhary <milindchoudhary@gmail.com>]

milind@arun:~/src/linux> egrep -rin "#define.*NAME_?OFFSET" .
./arch/alpha/kernel/osf_sys.c:95:#define NAME_OFFSET    offsetof (struct osf_dirent, d_name)
./arch/mips/kernel/sysirix.c:1738:#define NAME_OFFSET32(de) ((int) ((de)->d_name - (char *) (de)))
./arch/mips/kernel/sysirix.c:1840:#define NAME_OFFSET64(de) ((int) ((de)->d_name - (char *) (de)))
./arch/parisc/hpux/fs.c:72:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./arch/parisc/kernel/sys_parisc32.c:315:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./arch/powerpc/kernel/sys_ppc32.c:57:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./arch/sparc/kernel/sys_sunos.c:324:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./arch/sparc64/kernel/sys_sunos32.c:275:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./drivers/isdn/hardware/eicon/s_4bri.c:184:#define FPGA_NAME_OFFSET         0x10
./fs/compat.c:903:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./fs/readdir.c:54:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./include/linux/fuse.h:342:#define FUSE_NAME_OFFSET ((unsigned) ((struct fuse_dirent *) 0)->name)


just working out different options before putting it in kernel.h

as all the dirent structures have used the 
same name for the d_name member,so we can use

#define NAME_OFFSET(dirent) ((int) ((dirent)->d_name - (char __user *) (dirent)))

but then it becomes binding on the future users
 to maintain the same naming  convention.

#define NAME_OFFSET(dirent,d_name) ((int) ((dirent)->d_name - (char __user *) (dirent)))

#define NAME_OFFSET(dirent,d_name) offsetof(struct dirent,d_name)

though ..the first one seem to be just fine

thoughts

-- 
Milind Arun Choudhary