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Annotation of sys/dev/ic/pt2254a.c, Revision 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: }