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: }
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