add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/ibm/readclock.c

@@ -0,0 +1,140 @@
+/* readclock - read the AT real time clock	Authors: T. Holm & E. Froese */
+
+/************************************************************************/
+/*									*/
+/*   readclock.c							*/
+/*									*/
+/*		Read the AT real time clock, write the time to		*/
+/*		standard output in a form usable by date(1).		*/
+/*		If the system is an AT then the time is read		*/
+/*		from the built-in clock, and written to standard	*/
+/*		output in the form:					*/
+/*									*/
+/*			mmddyyhhmmss					*/
+/*									*/
+/*		If the system is not an AT then ``-q'' is written 	*/
+/*		to standard output. This is useful for placement in	*/
+/*		the ``/etc/rc'' script:					*/
+/*									*/
+/*	 	  /usr/bin/date `/usr/bin/readclock` </dev/tty  	*/
+/*									*/
+/************************************************************************/
+/*    origination          1987-Dec-29              efth                */
+/************************************************************************/
+
+
+
+#define CPU_TYPE_SEGMENT   0xFFFF	/* BIOS segment for CPU type 	 */
+#define CPU_TYPE_OFFSET    0x000E	/* BIOS offset for CPU type 	 */
+#define PC_AT              0xFC	/* IBM code for PC-AT (0xFFFFE) */
+#define PS_386		0xF8 /* IBM code for 386 PS/2's */	
+
+
+#define CLK_ELE 0x70		/* ptr corresponding to element of time to be*/
+#define CLK_IO 0x71		/* read or written is written to port clk_ele*/
+/* The element can then be read or written by */
+/* Reading or writing port clk_io.            */
+
+#define  YEAR             9	/* Clock register addresses	 */
+#define  MONTH            8
+#define  DAY              7
+#define  HOUR             4
+#define  MINUTE           2
+#define  SECOND           0
+#define  STATUS           0x0b
+
+#define  BCD_TO_DEC(x)	  ( (x>>4) * 10 + (x & 0x0f) )
+
+
+struct time {
+  unsigned year;
+  unsigned month;
+  unsigned day;
+  unsigned hour;
+  unsigned minute;
+  unsigned second;
+};
+
+
+
+main()
+{
+  struct time time1;
+  struct time time2;
+  int i;
+  int cpu_type;	
+
+  cpu_type = peek(CPU_TYPE_SEGMENT, CPU_TYPE_OFFSET);
+  if (cpu_type != PS_386 && cpu_type != PC_AT) {
+	printf("-q\n");
+	exit(1);
+  }
+  for (i = 0; i < 10; i++) {
+	get_time(&time1);
+	get_time(&time2);
+
+	if (time1.year == time2.year &&
+	    time1.month == time2.month &&
+	    time1.day == time2.day &&
+	    time1.hour == time2.hour &&
+	    time1.minute == time2.minute &&
+	    time1.second == time2.second) {
+		printf("%02d%02d%02d%02d%02d%02d\n",
+		       time1.month, time1.day, time1.year,
+		       time1.hour, time1.minute, time1.second);
+		exit(0);
+	}
+  }
+
+  printf("-q\n");
+  exit(1);
+}
+
+
+
+/***********************************************************************/
+/*                                                                     */
+/*    get_time( time )                                                 */
+/*                                                                     */
+/*    Update the structure pointed to by time with the current time    */
+/*    as read from the hardware real-time clock of the AT.             */
+/*    If necessary, the time is converted into a binary format before  */
+/*    being stored in the structure.                                   */
+/*                                                                     */
+/***********************************************************************/
+
+get_time(t)
+struct time *t;
+{
+  t->year = read_register(YEAR);
+  t->month = read_register(MONTH);
+  t->day = read_register(DAY);
+  t->hour = read_register(HOUR);
+  t->minute = read_register(MINUTE);
+  t->second = read_register(SECOND);
+
+
+
+  if ((read_register(STATUS) & 0x04) == 0) {
+	/* Convert BCD to binary if necessary */
+	t->year = BCD_TO_DEC(t->year);
+	t->month = BCD_TO_DEC(t->month);
+	t->day = BCD_TO_DEC(t->day);
+	t->hour = BCD_TO_DEC(t->hour);
+	t->minute = BCD_TO_DEC(t->minute);
+	t->second = BCD_TO_DEC(t->second);
+  }
+}
+
+
+read_register(reg_addr)
+char reg_addr;
+{
+  int val;
+
+  if (port_out(CLK_ELE, reg_addr) < 0 || port_in(CLK_IO, &val) < 0) {
+	printf("-q\n");
+	exit(1);
+  }
+  return(val);
+}