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Annotation of xinu/sys/slu6850.c, revision 1.1

1.1     ! root        1: #include "slu6850.h"
        !             2: /* Package to turn the write-only control register of each of up to MAXSLU
        !             3:    MC6850 SLUs into effectively read-write registers, and also initialize
        !             4:    the SLU for 8 bits, no parity, 1 stop bit, no interrupts.  To be
        !             5:    effective, all references to the control registers need to go
        !             6:    through this package. */
        !             7: 
        !             8: /* space for 3 saved regs-- */
        !             9: #define MAXSLU 3
        !            10: 
        !            11: static struct {
        !            12:   struct csr *csrptr;          /* which SLU this is */
        !            13:   char csrval;                 /* its current control reg val */
        !            14: }soft_control_reg[MAXSLU] = {0};
        !            15: 
        !            16: slu_init6850(csrptr)
        !            17: struct csr *csrptr;    /* ptr to device csr */
        !            18: {
        !            19:   int i;
        !            20: 
        !            21:   csrptr->cstat = SLURESET;    /* initialize the device */
        !            22:   for (i=0;i<10;i++) ;         /* wait a bit */
        !            23:   csrptr->cstat = SLUDEFAULT;
        !            24: 
        !            25:   /* lookup csr or set up new spot in array-- */
        !            26:   for (i=0;i<MAXSLU;i++) {
        !            27:     if (soft_control_reg[i].csrptr == (struct csr *)0) {
        !            28:       soft_control_reg[i].csrptr = csrptr; /* new spot */
        !            29:       break;
        !            30:     } else if (soft_control_reg[i].csrptr == csrptr)
        !            31:       break;
        !            32:   }
        !            33:   if (i<MAXSLU)
        !            34:     soft_control_reg[i].csrval = SLUDEFAULT;
        !            35:   else
        !            36:     panic("Too many SLU devs for soft_control_reg table");
        !            37: }
        !            38: 
        !            39: get_control_reg6850(csrptr)
        !            40: struct csr *csrptr;    /* ptr to device csr */
        !            41: {
        !            42:   int i;
        !            43: 
        !            44:   for (i=0;i<MAXSLU;i++)
        !            45:     if (soft_control_reg[i].csrptr == csrptr)
        !            46:       return soft_control_reg[i].csrval;
        !            47:   panic("Bad csrptr or uninitialized SLU");
        !            48: }
        !            49: 
        !            50: /* must be called to change control reg, so that software var is maintained */
        !            51: set_control_reg6850(csrptr,new_control)
        !            52: struct csr *csrptr;
        !            53: char new_control;
        !            54: {
        !            55:   int i;
        !            56: 
        !            57:   for (i=0;i<MAXSLU;i++)
        !            58:     if (soft_control_reg[i].csrptr == csrptr) {
        !            59:       soft_control_reg[i].csrval = new_control;
        !            60:       break;
        !            61:     }
        !            62:   if (i==MAXSLU)
        !            63:     panic("Bad csrptr or uninitialized SLU");
        !            64: 
        !            65:   csrptr->cstat = new_control; /* 6850--just one reg */
        !            66:   return 0;
        !            67: }
        !            68: 

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