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Annotation of qemu/hw/pcspk.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * QEMU PC speaker emulation
        !             3:  *
        !             4:  * Copyright (c) 2006 Joachim Henke
        !             5:  *
        !             6:  * Permission is hereby granted, free of charge, to any person obtaining a copy
        !             7:  * of this software and associated documentation files (the "Software"), to deal
        !             8:  * in the Software without restriction, including without limitation the rights
        !             9:  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
        !            10:  * copies of the Software, and to permit persons to whom the Software is
        !            11:  * furnished to do so, subject to the following conditions:
        !            12:  *
        !            13:  * The above copyright notice and this permission notice shall be included in
        !            14:  * all copies or substantial portions of the Software.
        !            15:  *
        !            16:  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
        !            17:  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
        !            19:  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
        !            20:  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
        !            21:  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
        !            22:  * THE SOFTWARE.
        !            23:  */
        !            24: 
        !            25: #include "vl.h"
        !            26: 
        !            27: #define PCSPK_BUF_LEN 1792
        !            28: #define PCSPK_SAMPLE_RATE 32000
        !            29: #define PCSPK_MAX_FREQ (PCSPK_SAMPLE_RATE >> 1)
        !            30: #define PCSPK_MIN_COUNT ((PIT_FREQ + PCSPK_MAX_FREQ - 1) / PCSPK_MAX_FREQ)
        !            31: 
        !            32: typedef struct {
        !            33:     uint8_t sample_buf[PCSPK_BUF_LEN];
        !            34:     QEMUSoundCard card;
        !            35:     SWVoiceOut *voice;
        !            36:     PITState *pit;
        !            37:     unsigned int pit_count;
        !            38:     unsigned int samples;
        !            39:     unsigned int play_pos;
        !            40:     int data_on;
        !            41:     int dummy_refresh_clock;
        !            42: } PCSpkState;
        !            43: 
        !            44: static const char *s_spk = "pcspk";
        !            45: static PCSpkState pcspk_state;
        !            46: 
        !            47: static inline void generate_samples(PCSpkState *s)
        !            48: {
        !            49:     unsigned int i;
        !            50: 
        !            51:     if (s->pit_count) {
        !            52:         const uint32_t m = PCSPK_SAMPLE_RATE * s->pit_count;
        !            53:         const uint32_t n = ((uint64_t)PIT_FREQ << 32) / m;
        !            54: 
        !            55:         /* multiple of wavelength for gapless looping */
        !            56:         s->samples = (PCSPK_BUF_LEN * PIT_FREQ / m * m / (PIT_FREQ >> 1) + 1) >> 1;
        !            57:         for (i = 0; i < s->samples; ++i)
        !            58:             s->sample_buf[i] = (64 & (n * i >> 25)) - 32;
        !            59:     } else {
        !            60:         s->samples = PCSPK_BUF_LEN;
        !            61:         for (i = 0; i < PCSPK_BUF_LEN; ++i)
        !            62:             s->sample_buf[i] = 128; /* silence */
        !            63:     }
        !            64: }
        !            65: 
        !            66: static void pcspk_callback(void *opaque, int free)
        !            67: {
        !            68:     PCSpkState *s = opaque;
        !            69:     unsigned int n;
        !            70: 
        !            71:     if (pit_get_mode(s->pit, 2) != 3)
        !            72:         return;
        !            73: 
        !            74:     n = pit_get_initial_count(s->pit, 2);
        !            75:     /* avoid frequencies that are not reproducible with sample rate */
        !            76:     if (n < PCSPK_MIN_COUNT)
        !            77:         n = 0;
        !            78: 
        !            79:     if (s->pit_count != n) {
        !            80:         s->pit_count = n;
        !            81:         s->play_pos = 0;
        !            82:         generate_samples(s);
        !            83:     }
        !            84: 
        !            85:     while (free > 0) {
        !            86:         n = audio_MIN(s->samples - s->play_pos, (unsigned int)free);
        !            87:         n = AUD_write(s->voice, &s->sample_buf[s->play_pos], n);
        !            88:         if (!n)
        !            89:             break;
        !            90:         s->play_pos = (s->play_pos + n) % s->samples;
        !            91:         free -= n;
        !            92:     }
        !            93: }
        !            94: 
        !            95: int pcspk_audio_init(AudioState *audio)
        !            96: {
        !            97:     PCSpkState *s = &pcspk_state;
        !            98:     audsettings_t as = {PCSPK_SAMPLE_RATE, 1, AUD_FMT_U8};
        !            99: 
        !           100:     if (!audio) {
        !           101:         AUD_log(s_spk, "No audio state\n");
        !           102:         return -1;
        !           103:     }
        !           104:     AUD_register_card(audio, s_spk, &s->card);
        !           105: 
        !           106:     s->voice = AUD_open_out(&s->card, s->voice, s_spk, s, pcspk_callback, &as, 0);
        !           107:     if (!s->voice) {
        !           108:         AUD_log(s_spk, "Could not open voice\n");
        !           109:         return -1;
        !           110:     }
        !           111: 
        !           112:     return 0;
        !           113: }
        !           114: 
        !           115: static uint32_t pcspk_ioport_read(void *opaque, uint32_t addr)
        !           116: {
        !           117:     PCSpkState *s = opaque;
        !           118:     int out;
        !           119: 
        !           120:     s->dummy_refresh_clock ^= (1 << 4);
        !           121:     out = pit_get_out(s->pit, 2, qemu_get_clock(vm_clock)) << 5;
        !           122: 
        !           123:     return pit_get_gate(s->pit, 2) | (s->data_on << 1) | s->dummy_refresh_clock | out;
        !           124: }
        !           125: 
        !           126: static void pcspk_ioport_write(void *opaque, uint32_t addr, uint32_t val)
        !           127: {
        !           128:     PCSpkState *s = opaque;
        !           129:     const int gate = val & 1;
        !           130: 
        !           131:     s->data_on = (val >> 1) & 1;
        !           132:     pit_set_gate(s->pit, 2, gate);
        !           133:     if (s->voice) {
        !           134:         if (gate) /* restart */
        !           135:             s->play_pos = 0;
        !           136:         AUD_set_active_out(s->voice, gate & s->data_on);
        !           137:     }
        !           138: }
        !           139: 
        !           140: void pcspk_init(PITState *pit)
        !           141: {
        !           142:     PCSpkState *s = &pcspk_state;
        !           143: 
        !           144:     s->pit = pit;
        !           145:     register_ioport_read(0x61, 1, 1, pcspk_ioport_read, s);
        !           146:     register_ioport_write(0x61, 1, 1, pcspk_ioport_write, s);
        !           147: }

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