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Annotation of sys/dev/ic/pt2254a.c, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: pt2254a.c,v 1.1 2002/04/25 04:56:59 mickey Exp $      */
                      2: /*
                      3:  * Copyright (c) 2002 Vladimir Popov <jumbo@narod.ru>.
                      4:  *
                      5:  * Redistribution and use in source and binary forms, with or without
                      6:  * modification, are permitted provided that the following conditions
                      7:  * are met:
                      8:  * 1. Redistributions of source code must retain the above copyright
                      9:  *    notice, this list of conditions and the following disclaimer.
                     10:  * 2. Redistributions in binary form must reproduce the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer in the
                     12:  *    documentation and/or other materials provided with the distribution.
                     13:  *
                     14:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
                     15:  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
                     16:  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
                     17:  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
                     18:  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
                     19:  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
                     20:  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
                     21:  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
                     22:  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
                     23:  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
                     24:  */
                     25: /*
                     26:  * Princeton Technology Corp.'s Electronic Volume Controller IC PT2254A
                     27:  *  http://www.princeton.com.tw
                     28:  *
                     29:  *  PT2254A is an electronic volume controller IC utilizing CMOS Technology
                     30:  *  specially designed for use in audio equipment. It has two built-in
                     31:  *  channels making it highly suitable for mono and stereo sound applications.
                     32:  *  Through the specially designated signals that are applied externally to
                     33:  *  the data, clock and strobe input pins, PT2254A can control attenuation
                     34:  *  and channel balance.
                     35:  */
                     36:
                     37: #include <sys/param.h>
                     38:
                     39: #include <dev/ic/pt2254a.h>
                     40:
                     41: u_int32_t
                     42: pt2254a_encode_volume(u_int8_t *current, u_int8_t max) {
                     43:        u_int32_t ret = 0ul;
                     44:        u_int8_t vol, tens, ones;
                     45:        int steps;
                     46:
                     47:        /*
                     48:         * Volume management is done nonlinear.
                     49:         *
                     50:         * Approximate the curve with three lines:
                     51:         * low volume:          y = - (48 /(max/3)) * x + 68
                     52:         * middle volume:       y = - (14 /(max/3)) * x + 34
                     53:         * high volume:         y = - (6 /(max/3)) * x + 18
                     54:         */
                     55:        if (*current > 0 && *current <= max / 3) {
                     56:                vol = PT2254A_MAX_ATTENUATION - (144 * (int)(*current) / max);
                     57:        } else if (*current > max / 3 && *current <= 2 * max / 3) {
                     58:                vol = 34 - (42 * (int)(*current) / max);
                     59:        } else if (*current > 2 * max / 3) {
                     60:                vol = 18 - (18 * (int)(*current) / max);
                     61:        } else vol = PT2254A_MAX_ATTENUATION;
                     62:
                     63:        /* Report adjusted volume */
                     64:        /* *current = max - (vol * max / PT2254A_MAX_ATTENUATION); */
                     65:        steps = *current * PT2254A_MAX_ATTENUATION / max;
                     66:        *current = steps * max / PT2254A_MAX_ATTENUATION;
                     67:
                     68:        tens = vol / 10;
                     69:        ones = vol - tens * 10;
                     70:
                     71:        ret = PT2254A_ATTENUATION_MAJOR(tens) | PT2254A_ATTENUATION_MINOR(ones);
                     72:
                     73:        return ret;
                     74: }
                     75:
                     76: u_int32_t
                     77: pt2254a_compose_register(u_int32_t lvol, u_int32_t rvol, int left, int right) {
                     78:        u_int32_t ret = 0ul;
                     79:
                     80:        if (left == USE_CHANNEL) {
                     81:                ret |= PT2254A_LEFT_CHANNEL;
                     82:                ret |= lvol;
                     83:        }
                     84:        if (right == USE_CHANNEL) {
                     85:                ret |= PT2254A_RIGHT_CHANNEL;
                     86:                ret |= rvol;
                     87:        }
                     88:
                     89:        ret |= PT2254A_ZERO_PADDING;
                     90:        ret |= PT2254A_EMPTY_BIT;
                     91:
                     92:        return ret;
                     93: }