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Annotation of 42BSD/sys/vax/clock.c, revision 1.1

1.1     ! root        1: /*     clock.c 6.1     83/07/29        */
        !             2: 
        !             3: #include "../h/param.h"
        !             4: #include "../h/time.h"
        !             5: #include "../h/kernel.h"
        !             6: 
        !             7: #include "../vax/mtpr.h"
        !             8: #include "../vax/clock.h"
        !             9: 
        !            10: /*
        !            11:  * Machine-dependent clock routines.
        !            12:  *
        !            13:  * Startrtclock restarts the real-time clock, which provides
        !            14:  * hardclock interrupts to kern_clock.c.
        !            15:  *
        !            16:  * Inittodr initializes the time of day hardware which provides
        !            17:  * date functions.  Its primary function is to use some file
        !            18:  * system information in case the hardare clock lost state.
        !            19:  *
        !            20:  * Resettodr restores the time of day hardware after a time change.
        !            21:  */
        !            22: 
        !            23: /*
        !            24:  * Start the real-time clock.
        !            25:  */
        !            26: startrtclock()
        !            27: {
        !            28: 
        !            29:        mtpr(NICR, -1000000/hz);
        !            30:        mtpr(ICCS, ICCS_RUN+ICCS_IE+ICCS_TRANS+ICCS_INT+ICCS_ERR);
        !            31: }
        !            32: 
        !            33: /*
        !            34:  * Initialze the time of day register, based on the time base which is, e.g.
        !            35:  * from a filesystem.  Base provides the time to within six months,
        !            36:  * and the time of year clock provides the rest.
        !            37:  */
        !            38: inittodr(base)
        !            39:        time_t base;
        !            40: {
        !            41:        register u_int todr = mfpr(TODR);
        !            42:        long deltat;
        !            43:        int year = YRREF;
        !            44: 
        !            45:        if (base < 5*SECYR) {
        !            46:                printf("WARNING: preposterous time in file system");
        !            47:                time.tv_sec = 6*SECYR + 186*SECDAY + SECDAY/2;
        !            48:                resettodr();
        !            49:                goto check;
        !            50:        }
        !            51:        /*
        !            52:         * TODRZERO is base used by VMS, which runs on local time.
        !            53:         */
        !            54:        if (todr < TODRZERO) {
        !            55:                printf("WARNING: todr too small");
        !            56:                time.tv_sec = base;
        !            57:                /*
        !            58:                 * Believe the time in the file system for lack of
        !            59:                 * anything better, resetting the TODR.
        !            60:                 */
        !            61:                resettodr();
        !            62:                goto check;
        !            63:        }
        !            64: 
        !            65:        /*
        !            66:         * Sneak to within 6 month of the time in the filesystem,
        !            67:         * by starting with the time of the year suggested by the TODR,
        !            68:         * and advancing through succesive years.  Adding the number of
        !            69:         * seconds in the current year takes us to the end of the current year
        !            70:         * and then around into the next year to the same position.
        !            71:         */
        !            72:        time.tv_sec = (todr-TODRZERO)/100;
        !            73:        while (time.tv_sec < base-SECYR/2) {
        !            74:                if (LEAPYEAR(year))
        !            75:                        time.tv_sec += SECDAY;
        !            76:                year++;
        !            77:                time.tv_sec += SECYR;
        !            78:        }
        !            79: 
        !            80:        /*
        !            81:         * See if we gained/lost two or more days;
        !            82:         * if so, assume something is amiss.
        !            83:         */
        !            84:        deltat = time.tv_sec - base;
        !            85:        if (deltat < 0)
        !            86:                deltat = -deltat;
        !            87:        if (deltat < 2*SECDAY)
        !            88:                return;
        !            89:        printf("WARNING: clock %s %d days",
        !            90:            time.tv_sec < base ? "lost" : "gained", deltat / SECDAY);
        !            91: check:
        !            92:        printf(" -- CHECK AND RESET THE DATE!\n");
        !            93: }
        !            94: 
        !            95: /*
        !            96:  * Reset the TODR based on the time value; used when the TODR
        !            97:  * has a preposterous value and also when the time is reset
        !            98:  * by the stime system call.  Also called when the TODR goes past
        !            99:  * TODRZERO + 100*(SECYEAR+2*SECDAY) (e.g. on Jan 2 just after midnight)
        !           100:  * to wrap the TODR around.
        !           101:  */
        !           102: resettodr()
        !           103: {
        !           104:        int year = YRREF;
        !           105:        u_int secyr;
        !           106:        u_int yrtime = time.tv_sec;
        !           107: 
        !           108:        /*
        !           109:         * Whittle the time down to an offset in the current year,
        !           110:         * by subtracting off whole years as long as possible.
        !           111:         */
        !           112:        for (;;) {
        !           113:                secyr = SECYR;
        !           114:                if (LEAPYEAR(year))
        !           115:                        secyr += SECDAY;
        !           116:                if (yrtime < secyr)
        !           117:                        break;
        !           118:                yrtime -= secyr;
        !           119:                year++;
        !           120:        }
        !           121:        mtpr(TODR, TODRZERO + yrtime*100);
        !           122: }

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