++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
				src/kernel/driver.h	 	 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

09000	/* Types and constants shared between the generic and device dependent
09001	 * device driver code.
09002	 */

09009	/* Info about and entry points into the device dependent code. */
09010	struct driver {
09011	  _PROTOTYPE( char *(*dr_name), (void) );
09012	  _PROTOTYPE( int (*dr_open), (struct driver *dp, message *m_ptr) );
09013	  _PROTOTYPE( int (*dr_close), (struct driver *dp, message *m_ptr) );
09014	  _PROTOTYPE( int (*dr_ioctl), (struct driver *dp, message *m_ptr) );
09015	  _PROTOTYPE( struct device *(*dr_prepare), (int device) );
09016	  _PROTOTYPE( int (*dr_schedule), (int proc_nr, struct iorequest_s *request) );
09017	  _PROTOTYPE( int (*dr_finish), (void) );
09018	  _PROTOTYPE( void (*dr_cleanup), (void) );
09019	  _PROTOTYPE( void (*dr_geometry), (struct partition *entry) );
09020	};

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
				src/kernel/driver.c	 	 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

09141	/*===========================================================================*
09142	 *                              driver_task                                  *
09143	 *===========================================================================*/
09144	PUBLIC void driver_task(dp)
09145	struct driver *dp;      /* Device dependent entry points. */
09146	{
09147	/* Main program of any device driver task. */
09148	
09149	  int r, caller, proc_nr;
09150	  message mess;
09151	
09152	  init_buffer();        /* Get a DMA buffer. */
09153	
09154	  /* Here is the main loop of the disk task.  It waits for a message, carries
09155	   * it out, and sends a reply.
09156	   */
09157	
09158	  while (TRUE) {
09159	        /* First wait for a request to read or write a disk block. */
09160	        receive(ANY, &mess);
09161	
09162	        caller = mess.m_source;
09163	        proc_nr = mess.PROC_NR;
09164	
09165	        switch (caller) {
09166	        case HARDWARE:
09167	                /* Leftover interrupt. */
09168	                continue;
09169	        case FS_PROC_NR:
09170	                /* The only legitimate caller. */
09171	                break;
09172	        default:
09173	                printf("%s: got message from %d\n", (*dp->dr_name)(), caller);
09174	                continue;
09175	        }
09176	
09177	        /* Now carry out the work. */
09178	        switch(mess.m_type) {
09179	            case DEV_OPEN:      r = (*dp->dr_open)(dp, &mess);  break;
09180	            case DEV_CLOSE:     r = (*dp->dr_close)(dp, &mess); break;
09181	            case DEV_IOCTL:     r = (*dp->dr_ioctl)(dp, &mess); break;
09182	
09183	            case DEV_READ:
09184	            case DEV_WRITE:     r = do_rdwt(dp, &mess);         break;
09185	
09186	            case SCATTERED_IO:  r = do_vrdwt(dp, &mess);        break;
09187	            default:            r = EINVAL;                     break;
09188	        }
09189	
09190	        /* Clean up leftover state. */
09191	        (*dp->dr_cleanup)();
09192	
09193	        /* Finally, prepare and send the reply message. */
09194	        mess.m_type = TASK_REPLY;
09195	        mess.REP_PROC_NR = proc_nr;
09196	
09197	        mess.REP_STATUS = r;    /* # of bytes transferred or error code */
09198	        send(caller, &mess);    /* send reply to caller */
09199	  }
09200	}