--- /dev/null
+/*
+ * This file is part of DisOrder
+ * Copyright (C) 2007 Richard Kettlewell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+/** @file lib/mixer-alsa.c
+ * @brief ALSA mixer support
+ *
+ * The documentation for ALSA's mixer support is completely hopeless,
+ * which is a particular nuisnace given it's got an incredibly verbose
+ * API. Much of this code is cribbed from
+ * alsa-utils-1.0.13/amixer/amixer.c.
+ *
+ * Mono output devices are supported, but the support is not tested
+ * (as I don't one).
+ */
+
+#include <config.h>
+
+#if HAVE_ALSA_ASOUNDLIB_H
+
+#include "types.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stddef.h>
+#include <ctype.h>
+#include <sys/ioctl.h>
+#include <alsa/asoundlib.h>
+
+#include "configuration.h"
+#include "mixer.h"
+#include "log.h"
+#include "syscalls.h"
+
+/** @brief Shared state for ALSA mixer support */
+struct alsa_mixer_state {
+ /** @brief Mixer handle */
+ snd_mixer_t *handle;
+
+ /** @brief Mixer control */
+ snd_mixer_elem_t *elem;
+
+ /** @brief Left channel */
+ snd_mixer_selem_channel_id_t left;
+
+ /** @brief Right channel */
+ snd_mixer_selem_channel_id_t right;
+
+ /** @brief Minimum level */
+ long min;
+
+ /** @brief Maximum level */
+ long max;
+};
+
+/** @brief Destroy a @ref alsa_mixer_state */
+static void alsa_close(struct alsa_mixer_state *h) {
+ /* TODO h->elem */
+ if(h->handle)
+ snd_mixer_close(h->handle);
+}
+
+/** @brief Initialize a @ref alsa_mixer_state */
+static int alsa_open(struct alsa_mixer_state *h) {
+ int err;
+ snd_mixer_selem_id_t *id;
+
+ snd_mixer_selem_id_alloca(&id);
+ memset(h, 0, sizeof h);
+ if((err = snd_mixer_open(&h->handle, 0))) {
+ error(0, "snd_mixer_open: %s", snd_strerror(err));
+ return -1;
+ }
+ if((err = snd_mixer_attach(h->handle, config->device))) {
+ error(0, "snd_mixer_attach %s: %s",
+ config->device, snd_strerror(err));
+ goto error;
+ }
+ if((err = snd_mixer_selem_register(h->handle, 0/*options*/, 0/*classp*/))) {
+ error(0, "snd_mixer_selem_register %s: %s",
+ config->device, snd_strerror(err));
+ goto error;
+ }
+ if((err = snd_mixer_load(h->handle))) {
+ error(0, "snd_mixer_load %s: %s",
+ config->device, snd_strerror(err));
+ goto error;
+ }
+ snd_mixer_selem_id_set_name(id, config->channel);
+ snd_mixer_selem_id_set_index(id, atoi(config->mixer));
+ if(!(h->elem = snd_mixer_find_selem(h->handle, id))) {
+ error(0, "snd_mixer_find_selem returned NULL");
+ goto error;
+ }
+ if(!snd_mixer_selem_has_playback_volume(h->elem)) {
+ error(0, "configured mixer control has no playback volume");
+ goto error;
+ }
+ if(snd_mixer_selem_is_playback_mono(h->elem)) {
+ h->left = h->right = SND_MIXER_SCHN_MONO;
+ } else {
+ h->left = SND_MIXER_SCHN_FRONT_LEFT;
+ h->right = SND_MIXER_SCHN_FRONT_RIGHT;
+ }
+ if(!snd_mixer_selem_has_playback_channel(h->elem, h->left)
+ || !snd_mixer_selem_has_playback_channel(h->elem, h->right)) {
+ error(0, "configured mixer control lacks required playback channels");
+ goto error;
+ }
+ snd_mixer_selem_get_playback_volume_range(h->elem, &h->min, &h->max);
+ return 0;
+error:
+ alsa_close(h);
+ return -1;
+}
+
+/** @brief Convert a level to a percentage */
+static int to_percent(const struct alsa_mixer_state *h, long n) {
+ return (n - h->min) * 100 / (h->max - h->min);
+}
+
+/** @brief Get ALSA volume */
+static int alsa_get(int *left, int *right) {
+ struct alsa_mixer_state h[1];
+ long l, r;
+ int err;
+
+ if(alsa_open(h))
+ return -1;
+ if((err = snd_mixer_selem_get_playback_volume(h->elem, h->left, &l))
+ || (err = snd_mixer_selem_get_playback_volume(h->elem, h->right, &r))) {
+ error(0, "snd_mixer_selem_get_playback_volume: %s", snd_strerror(err));
+ goto error;
+ }
+ *left = to_percent(h, l);
+ *right = to_percent(h, r);
+ alsa_close(h);
+ return 0;
+error:
+ alsa_close(h);
+ return -1;
+}
+
+/** @brief Convert a percentage to a level */
+static int from_percent(const struct alsa_mixer_state *h, int n) {
+ return h->min + n * (h->max - h->min) / 100;
+}
+
+/** @brief Set ALSA volume */
+static int alsa_set(int *left, int *right) {
+ struct alsa_mixer_state h[1];
+ long l, r;
+ int err;
+
+ if(alsa_open(h))
+ return -1;
+ /* Set the volume */
+ if(h->left == h->right) {
+ /* Mono output - just use the loudest */
+ if((err = snd_mixer_selem_set_playback_volume
+ (h->elem, h->left,
+ from_percent(h, *left > *right ? *left : *right)))) {
+ error(0, "snd_mixer_selem_set_playback_volume: %s", snd_strerror(err));
+ goto error;
+ }
+ } else {
+ /* Stereo output */
+ if((err = snd_mixer_selem_set_playback_volume
+ (h->elem, h->left, from_percent(h, *left)))
+ || (err = snd_mixer_selem_set_playback_volume
+ (h->elem, h->right, from_percent(h, *right)))) {
+ error(0, "snd_mixer_selem_set_playback_volume: %s", snd_strerror(err));
+ goto error;
+ }
+ }
+ /* Read it back to see what we ended up at */
+ if((err = snd_mixer_selem_get_playback_volume(h->elem, h->left, &l))
+ || (err = snd_mixer_selem_get_playback_volume(h->elem, h->right, &r))) {
+ error(0, "snd_mixer_selem_get_playback_volume: %s", snd_strerror(err));
+ goto error;
+ }
+ *left = to_percent(h, l);
+ *right = to_percent(h, r);
+ alsa_close(h);
+ return 0;
+error:
+ alsa_close(h);
+ return -1;
+}
+
+/** @brief ALSA mixer vtable */
+const struct mixer mixer_alsa = {
+ BACKEND_ALSA,
+ alsa_get,
+ alsa_set,
+ "0",
+ "PCM"
+};
+#endif
+
+/*
+Local Variables:
+c-basic-offset:2
+comment-column:40
+End:
+*/
~mdw / disorder / blobdiff