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Annotation of coherent/f/usr/man/KERNEL/altclk_in, revision 1.1

1.1     ! root        1: aallttccllkk_iinn() -- Accessible Kernel Routine
        !             2: 
        !             3: iinntt
        !             4: aallttccllkk_iinn(_h_z, _f_n)
        !             5: iinntt _h_z, (*_f_n)();
        !             6: 
        !             7: aallttccllkk_iinn() increases the system clock  rate from the value set by manifest
        !             8: constant HHZZ (at present, 100 Hertz) to _h_z. Function _f_n will be called every
        !             9: time the  clock interrupt occurs.  _h_z  must be an integral  multiple of HHZZ;
        !            10: therefore, the  rate of clock interrupts  will be increased by  a factor of
        !            11: _h_z/HHZZ.  _f_n is an iinntt-valued function that must return 0 every _h_z/HHZZ'th time
        !            12: it is called,  nonzero the rest of the time.   The zero value returned from
        !            13: _f_n tells the COHERENT system's clock routine to do its usual processing.
        !            14: 
        !            15: aallttccllkk_iinn() returns 0 if it completes normally; if argument _h_z is less than
        !            16: HHZZ  or not  an integral  multiple  of HHZZ,  this function  does nothing  and
        !            17: returns -1.
        !            18: 
        !            19: _E_x_a_m_p_l_e
        !            20: The following gives a partial example of how to use aallttccllkk_iinn() in a device
        !            21: driver.
        !            22: 
        !            23: #include <sys/const.h>  /* #define's HZ */
        !            24: ...
        !            25: 
        !            26: static int scale_factor;
        !            27: static int poll_fn();
        !            28: ...
        !            29: 
        !            30:     /* install high-speed polling of I/O device */
        !            31:     poll_rate = ...;
        !            32:     scale_factor = poll_rate/HZ;
        !            33:     altclk_out();
        !            34:     altclk_in(poll_rate, poll_fn);
        !            35: ...
        !            36: 
        !            37: /* polling function */
        !            38: int poll_fn()
        !            39: {
        !            40:     static int count;
        !            41: 
        !            42:     ...do device polling...
        !            43: 
        !            44:     count++;
        !            45:     if (count >= scale_factor)
        !            46:         count = 0;
        !            47:     return count;
        !            48: }
        !            49: 
        !            50: _S_e_e _A_l_s_o
        !            51: aacccceessssiibbllee kkeerrnneell rroouuttiinneess, aallttccllkk_oouutt()
        !            52: 
        !            53: _N_o_t_e_s
        !            54: Avoid  naming the  polling  function aallttccllkk():  there is  already a  kernel
        !            55: symbol with this name.

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