TCP-IP红宝书源代码

				/* control.c - control */
				
				#include 
				#include 
				#include 
				#include 
				
				/*------------------------------------------------------------------------
				 *  control  -  control a device (e.g., set the mode)
				 *------------------------------------------------------------------------
				 */
				SYSCALL
				control(int descrp, int func, ...)
				{
					va_list		ap;
					struct	devsw	*pdev;
					void		*arg1, *arg2;
					int		rv;
				
					va_start(ap, func);
					if (isbaddev(descrp) )
						return SYSERR;
					pdev = &devtab[descrp];
					arg1 = va_arg(ap, void *);
					arg2 = va_arg(ap, void *);
					rv = (*pdev->dvcntl)(pdev, func, arg1, arg2);
					va_end(ap);
					return rv;
				}