diff options
Diffstat (limited to 'io.c')
| -rw-r--r-- | io.c | 192 |
1 files changed, 192 insertions, 0 deletions
@@ -0,0 +1,192 @@ +/*
+ * IO functionality
+ * for MPX-OS
+ * Ben Burwell & Averill Morash
+ * CSI350 - Fall 2013
+ */
+
+#include <dos.h>
+#include <stdio.h>
+#include "mpx.h"
+
+#define DS_OFFSET 6 // was 3 before
+
+int count = 0;
+void IO_sup(pcb *p) {
+ char far *buffer;
+ int far *length;
+ unsigned *ds_add;
+ int con_w = 0;
+ int rc;
+
+ disable();
+
+ if (DEBUG_PRINTS) { printf("in io_sup \n");}
+
+ //make the far pointers (see page 107)
+ ds_add = p->stack_ptr + DS_OFFSET;
+ buffer = MK_FP(*ds_add, p->parm_add->buffer);
+ length = MK_FP(*ds_add, p->parm_add->length);
+
+ //call com_read or equivalent
+ switch (p->parm_add->op_number){
+ case COM:
+ // IO_sched should have validated input
+ // Assume that op_type is either read or write
+ if (p->parm_add->op_type == READ) {
+ if (DEBUG_PRINTS){printf("com read req \n");}
+ com_eflag = 0;
+ rc = com_read(buffer, length);
+ } else {
+ if (DEBUG_PRINTS) {printf("com write req \n");}
+ com_eflag = 0;
+ rc = com_write(buffer, length);
+ }
+ break;
+ case CON:
+ if (p->parm_add->op_type == READ) {
+ if (DEBUG_PRINTS){printf("con read req\n");}
+ con_eflag = 0;
+ con.current_op = READ_OP;
+ rc = con_read(buffer, length);
+ } else {
+ if (DEBUG_PRINTS){printf("con_write req\n");}
+ con_w = 1;
+ rc = con_write(buffer, length);
+ }
+ break;
+ case PRT:
+ if (DEBUG_PRINTS){printf("prt write req\n");}
+ prt_eflag = 0;
+ rc = prt_write(buffer, length);
+ break;
+ }
+
+ if (rc < 0) {
+ printf("Somthing went wrong in io_sup\n");
+ }
+
+ // put the pcb back in the ready queue, if it was a con_write
+ if (con_w == 1) {
+ insert_pcb(&ready_queue_locked, p,0);
+ }
+ enable();
+ return;
+}
+
+// Handle completion of an IO request
+int IO_complete(int device, int *stk_ptr) {
+
+ pcb *current;
+ dcb *d;
+
+ disable();
+ switch (device){
+ case CON:
+ d = &con;
+ d->current_op = NO_OP;
+ break;
+ case COM:
+ d = &com;
+ break;
+ case PRT:
+ d = &prt;
+ break;
+ }
+
+ if (DEBUG_PRINTS){printf("in io complete\n");}
+
+ // save interrupted process's stack pointer
+ cop->stack_ptr = stk_ptr;
+
+ // insert running process into ready queue
+ insert_pcb(&ready_queue_locked, cop, 0);
+
+ // set running process to ready state
+ cop->state = READY;
+
+ // get address of PCB whose IO just completed
+ current = d->current_pcb;
+
+ // insert into ready queue
+ insert_pcb(&ready_queue_locked, current, 0);
+
+ // set its state to ready
+ current->state = READY;
+
+ if (strcmp(d->current_pcb->name, "iocom2")==0) {
+ count++;
+ if (count > 20) {
+ d = &com;
+ }
+ }
+ if (d->pcb_head != NULL) {
+ // if there are pending IO requests for this device
+ //schedule them (IO_sched)
+ remove_pcb(&(d->pcb_head), d->pcb_head);
+ IO_sched(d->pcb_head);
+ }
+
+ outportb(0x20,0x20); // EOI signal
+ enable();
+ dispatch();
+
+ return 0;
+}
+
+// Service an IO request
+// Returns:
+// 0 for success
+// -1 for invalid operation
+// -2 for invalid device
+int IO_sched(pcb *p) {
+
+ dcb *d;
+ int op_num;
+ int op_type;
+
+ if (DEBUG_PRINTS) {printf("in io sched\n");}
+
+ // determine which device is requested
+ op_num = p->parm_add->op_number;
+ op_type = p->parm_add->op_type;
+
+ switch (op_num) {
+ case CON:
+ if (op_type != READ
+ && op_type != WRITE) {
+ return -1;
+ }
+ d = &con;
+ break;
+ case COM:
+ if (op_type != READ
+ && op_type != WRITE) {
+ return -1;
+ }
+ d = &com;
+ break;
+ case PRT:
+ if (op_type != WRITE) {
+ return -1;
+ }
+ d = &prt;
+ break;
+ default:
+ return -2;
+ }
+
+ if (d->current_op != NO_OP) {
+ disable();
+ // put pcb in IO queue
+ insert_pcb(&(d->pcb_head), p, 1);
+ // take pcb out of ready q
+ remove_pcb(&ready_queue_locked, p);
+ enable();
+ } else {
+ d->current_pcb = p;
+ IO_sup(p);
+ }
+
+ return 0;
+}
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