Help me understand this function title. Code from FreeBSD 8 source code UFS part

 /*
  180  * Create a regular file
  181  */
  182 static int
  183 ufs_create(ap)
  184 开发者_运维知识库        struct vop_create_args /* {
  185                 struct vnode *a_dvp;
  186                 struct vnode **a_vpp;
  187                 struct componentname *a_cnp;
  188                 struct vattr *a_vap;
  189         } */ *ap;
  190 {
  191         int error;
  192 
  193         error =
  194             ufs_makeinode(MAKEIMODE(ap->a_vap->va_type, ap->a_vap->va_mode),
  195             ap->a_dvp, ap->a_vpp, ap->a_cnp);
  196         if (error)
  197                 return (error);
  198         return (0);
  199 }

Please help me to get information from line 182-189...this is strange for me.. What is this function title means? (I mean, what is return value, what is input parameter?) Thank you all.

The return type is int and it takes one argument, a struct vop_create_args* named ap. This is K&R notation.

It's an old-style (pre-prototype) function declaration. The function is local to the current translation unit, returns an int, ap is the parameter it accepts and it's of the type:

struct vop_create_args *

All that other stuff is just comments, presumably echoing the actual definition of the structure so that the information is held locally as well (so a lazy coder doesn't have to go looking for it, a somewhat dangerous practice if the actual and local definitions get out of step).

It's equivalent to:

static int ufs_create (struct vop_create_args *ap) { ...