Initial contribution

4 files changed, 808 insertions, 0 deletions

diff --git a/Android.mk b/Android.mk
new file mode 100644
index 0000000..3266b93
--- /dev/null
+++ b/Android.mk
@@ -0,0 +1,10 @@
+LOCAL_PATH:= $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_C_INCLUDES:= external/tinyalsa/include
+LOCAL_SRC_FILES:= mixer.c pcm.c
+LOCAL_MODULE := libtinyalsa
+LOCAL_SHARED_LIBRARIES:= libcutils libutils
+LOCAL_MODULE_TAGS := optional
+
+include $(BUILD_SHARED_LIBRARY)
diff --git a/include/tinyalsa/asoundlib.h b/include/tinyalsa/asoundlib.h
new file mode 100644
index 0000000..38d3af1
--- /dev/null
+++ b/include/tinyalsa/asoundlib.h
@@ -0,0 +1,115 @@
+/* asoundlib.h
+**
+** Copyright 2011, The Android Open Source Project
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of The Android Open Source Project nor the names of
+**       its contributors may be used to endorse or promote products derived
+**       from this software without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED BY The Android Open Source Project ``AS IS'' AND
+** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+** ARE DISCLAIMED. IN NO EVENT SHALL The Android Open Source Project BE LIABLE
+** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+** DAMAGE.
+*/
+
+#ifndef ASOUNDLIB_H
+#define ASOUNDLIB_H
+
+
+/*
+ * PCM API
+ */
+
+struct pcm;
+
+#define PCM_OUT        0x00000000
+#define PCM_IN         0x10000000
+
+/* Bit formats */
+enum pcm_format {
+    PCM_FORMAT_S16_LE = 0,
+    PCM_FORMAT_S32_LE,
+
+    PCM_FORMAT_MAX,
+};
+
+/* Configuration for a stream */
+struct pcm_config {
+    unsigned int channels;
+    unsigned int rate;
+    unsigned int period_size;
+    unsigned int period_count;
+    enum pcm_format format;
+};
+
+/* Open and close a stream */
+struct pcm *pcm_open(unsigned int device, unsigned int flags, struct pcm_config *config);
+int pcm_close(struct pcm *pcm);
+int pcm_is_ready(struct pcm *pcm);
+
+/* Set and get config */
+int pcm_get_config(struct pcm *pcm, struct pcm_config *config);
+int pcm_set_config(struct pcm *pcm, struct pcm_config *config);
+
+/* Returns a human readable reason for the last error */
+const char *pcm_get_error(struct pcm *pcm);
+
+/* Returns the buffer size (int bytes) that should be used for pcm_write.
+ * This will be 1/2 of the actual fifo size.
+ */
+unsigned int pcm_get_buffer_size(struct pcm *pcm);
+
+/* Returns the pcm latency in ms */
+unsigned int pcm_get_latency(struct pcm *pcm);
+
+/* Write data to the fifo.
+ * Will start playback on the first write or on a write that
+ * occurs after a fifo underrun.
+ */
+int pcm_write(struct pcm *pcm, void *data, unsigned int count);
+int pcm_read(struct pcm *pcm, void *data, unsigned int count);
+
+
+/*
+ * MIXER API
+ */
+
+struct mixer;
+struct mixer_ctl;
+
+/* Open and close a mixer */
+struct mixer *mixer_open(unsigned int device);
+void mixer_close(struct mixer *mixer);
+
+/* Obtain mixer controls */
+int mixer_get_num_ctls(struct mixer *mixer);
+struct mixer_ctl *mixer_get_ctl(struct mixer *mixer, unsigned int id);
+struct mixer_ctl *mixer_get_ctl_by_name(struct mixer *mixer, const char *name);
+
+/* Set and get mixer controls */
+int mixer_ctl_get_percent(struct mixer_ctl *ctl);
+int mixer_ctl_set_percent(struct mixer_ctl *ctl, int percent);
+
+int mixer_ctl_get_int(struct mixer_ctl *ctl);
+int mixer_ctl_set_int(struct mixer_ctl *ctl, int);
+int mixer_ctl_get_step(struct mixer_ctl *ctl);
+
+int mixer_ctl_get_enum(struct mixer_ctl *ctl, const char *string, unsigned int size);
+int mixer_ctl_set_enum(struct mixer_ctl *ctl, unsigned int id);
+int mixer_ctl_set_enum_by_name(struct mixer_ctl *ctl, const char *string);
+
+#endif
diff --git a/mixer.c b/mixer.c
new file mode 100644
index 0000000..9c7e3b5
--- /dev/null
+++ b/mixer.c
@@ -0,0 +1,332 @@
+/* mixer.c
+**
+** Copyright 2011, The Android Open Source Project
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of The Android Open Source Project nor the names of
+**       its contributors may be used to endorse or promote products derived
+**       from this software without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED BY The Android Open Source Project ``AS IS'' AND
+** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+** ARE DISCLAIMED. IN NO EVENT SHALL The Android Open Source Project BE LIABLE
+** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+** DAMAGE.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <ctype.h>
+
+#include <linux/ioctl.h>
+#define __force
+#define __bitwise
+#define __user
+#include <sound/asound.h>
+
+#include <tinyalsa/asoundlib.h>
+
+static const char *elem_iface_name(snd_ctl_elem_iface_t n)
+{
+    switch (n) {
+    case SNDRV_CTL_ELEM_IFACE_CARD: return "CARD";
+    case SNDRV_CTL_ELEM_IFACE_HWDEP: return "HWDEP";
+    case SNDRV_CTL_ELEM_IFACE_MIXER: return "MIXER";
+    case SNDRV_CTL_ELEM_IFACE_PCM: return "PCM";
+    case SNDRV_CTL_ELEM_IFACE_RAWMIDI: return "MIDI";
+    case SNDRV_CTL_ELEM_IFACE_TIMER: return "TIMER";
+    case SNDRV_CTL_ELEM_IFACE_SEQUENCER: return "SEQ";
+    default: return "???";
+    }
+}
+
+static const char *elem_type_name(snd_ctl_elem_type_t n)
+{
+    switch (n) {
+    case SNDRV_CTL_ELEM_TYPE_NONE: return "NONE";
+    case SNDRV_CTL_ELEM_TYPE_BOOLEAN: return "BOOL";
+    case SNDRV_CTL_ELEM_TYPE_INTEGER: return "INT32";
+    case SNDRV_CTL_ELEM_TYPE_ENUMERATED: return "ENUM";
+    case SNDRV_CTL_ELEM_TYPE_BYTES: return "BYTES";
+    case SNDRV_CTL_ELEM_TYPE_IEC958: return "IEC958";
+    case SNDRV_CTL_ELEM_TYPE_INTEGER64: return "INT64";
+    default: return "???";
+    }
+}
+
+
+struct mixer_ctl {
+    struct mixer *mixer;
+    struct snd_ctl_elem_info *info;
+    char **ename;
+};
+
+struct mixer {
+    int fd;
+    struct snd_ctl_elem_info *info;
+    struct mixer_ctl *ctl;
+    unsigned int count;
+};
+
+void mixer_close(struct mixer *mixer)
+{
+    unsigned int n,m;
+
+    if (mixer->fd >= 0)
+        close(mixer->fd);
+
+    if (mixer->ctl) {
+        for (n = 0; n < mixer->count; n++) {
+            if (mixer->ctl[n].ename) {
+                unsigned int max = mixer->ctl[n].info->value.enumerated.items;
+                for (m = 0; m < max; m++)
+                    free(mixer->ctl[n].ename[m]);
+                free(mixer->ctl[n].ename);
+            }
+        }
+        free(mixer->ctl);
+    }
+
+    if (mixer->info)
+        free(mixer->info);
+
+    free(mixer);
+
+    /* TODO: verify frees */
+}
+
+struct mixer *mixer_open(unsigned int device)
+{
+    struct snd_ctl_elem_list elist;
+    struct snd_ctl_elem_info tmp;
+    struct snd_ctl_elem_id *eid = NULL;
+    struct mixer *mixer = NULL;
+    unsigned int n, m;
+    int fd;
+
+    fd = open("/dev/snd/controlC0", O_RDWR);
+    if (fd < 0)
+        return 0;
+
+    memset(&elist, 0, sizeof(elist));
+    if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_LIST, &elist) < 0)
+        goto fail;
+
+    mixer = calloc(1, sizeof(*mixer));
+    if (!mixer)
+        goto fail;
+
+    mixer->ctl = calloc(elist.count, sizeof(struct mixer_ctl));
+    mixer->info = calloc(elist.count, sizeof(struct snd_ctl_elem_info));
+    if (!mixer->ctl || !mixer->info)
+        goto fail;
+
+    eid = calloc(elist.count, sizeof(struct snd_ctl_elem_id));
+    if (!eid)
+        goto fail;
+
+    mixer->count = elist.count;
+    mixer->fd = fd;
+    elist.space = mixer->count;
+    elist.pids = eid;
+    if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_LIST, &elist) < 0)
+        goto fail;
+
+    for (n = 0; n < mixer->count; n++) {
+        struct snd_ctl_elem_info *ei = mixer->info + n;
+        ei->id.numid = eid[n].numid;
+        if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_INFO, ei) < 0)
+            goto fail;
+        mixer->ctl[n].info = ei;
+        mixer->ctl[n].mixer = mixer;
+        if (ei->type == SNDRV_CTL_ELEM_TYPE_ENUMERATED) {
+            char **enames = calloc(ei->value.enumerated.items, sizeof(char*));
+            if (!enames)
+                goto fail;
+            mixer->ctl[n].ename = enames;
+            for (m = 0; m < ei->value.enumerated.items; m++) {
+                memset(&tmp, 0, sizeof(tmp));
+                tmp.id.numid = ei->id.numid;
+                tmp.value.enumerated.item = m;
+                if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_INFO, &tmp) < 0)
+                    goto fail;
+                enames[m] = strdup(tmp.value.enumerated.name);
+                if (!enames[m])
+                    goto fail;
+            }
+        }
+    }
+
+    free(eid);
+    return mixer;
+
+fail:
+    /* TODO: verify frees in failure case */
+    if (eid)
+        free(eid);
+    if (mixer)
+        mixer_close(mixer);
+    else if (fd >= 0)
+        close(fd);
+    return 0;
+}
+
+int mixer_get_num_ctls(struct mixer *mixer)
+{
+    return mixer->count;
+}
+
+struct mixer_ctl *mixer_get_ctl(struct mixer *mixer, unsigned int id)
+{
+    if (id < mixer->count)
+        return mixer->ctl + id;
+
+    return NULL;
+}
+
+struct mixer_ctl *mixer_get_ctl_by_name(struct mixer *mixer, const char *name)
+{
+    unsigned int n;
+    for (n = 0; n < mixer->count; n++)
+        if (!strcmp(name, (char*) mixer->info[n].id.name))
+            return mixer->ctl + n;
+
+    return NULL;
+}
+
+static int percent_to_int(struct snd_ctl_elem_info *ei, int percent)
+{
+    int range;
+    
+    if (percent > 100)
+        percent = 100;
+    else if (percent < 0)
+        percent = 0;
+    
+    range = (ei->value.integer.max - ei->value.integer.min);
+    
+    return ei->value.integer.min + (range * percent) / 100;
+}
+
+static int int_to_percent(struct snd_ctl_elem_info *ei, int value)
+{
+    int range = (ei->value.integer.max - ei->value.integer.min);
+    
+    if (range == 0)
+        return 0;
+    
+    return ((value - ei->value.integer.min) / range) * 100;
+}
+
+int mixer_ctl_get_percent(struct mixer_ctl *ctl)
+{
+    struct snd_ctl_elem_value ev;
+
+    memset(&ev, 0, sizeof(ev));
+    ev.id.numid = ctl->info->id.numid;
+    if (ioctl(ctl->mixer->fd, SNDRV_CTL_IOCTL_ELEM_READ, &ev))
+        return -1;
+
+    switch (ctl->info->type) {
+    case SNDRV_CTL_ELEM_TYPE_BOOLEAN:
+        return !!ev.value.integer.value[0]; /* TODO: handle multiple return values */
+        break;
+    case SNDRV_CTL_ELEM_TYPE_INTEGER: {
+        return int_to_percent(ctl->info, ev.value.integer.value[0]);
+        break;
+    }
+    default:
+        errno = EINVAL;
+        return -1;
+    }
+
+    return 0;
+}
+
+int mixer_ctl_set_percent(struct mixer_ctl *ctl, int percent)
+{
+    struct snd_ctl_elem_value ev;
+    unsigned int n;
+
+    memset(&ev, 0, sizeof(ev));
+    ev.id.numid = ctl->info->id.numid;
+    switch (ctl->info->type) {
+    case SNDRV_CTL_ELEM_TYPE_BOOLEAN:
+        for (n = 0; n < ctl->info->count; n++)
+            ev.value.integer.value[n] = !!percent; /* TODO: handle multiple set values */
+        break;
+
+    case SNDRV_CTL_ELEM_TYPE_INTEGER: {
+        int value = percent_to_int(ctl->info, percent);
+        for (n = 0; n < ctl->info->count; n++)
+            ev.value.integer.value[n] = value;
+        break;
+    }
+
+    default:
+        errno = EINVAL;
+        return -1;
+    }
+    
+    return ioctl(ctl->mixer->fd, SNDRV_CTL_IOCTL_ELEM_WRITE, &ev);
+}
+
+int mixer_ctl_set_enum(struct mixer_ctl *ctl, unsigned int id)
+{
+    struct snd_ctl_elem_value ev;
+
+    if ((ctl->info->type != SNDRV_CTL_ELEM_TYPE_ENUMERATED) ||
+        (id >= ctl->info->value.enumerated.items)) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    memset(&ev, 0, sizeof(ev));
+    ev.value.enumerated.item[0] = id;
+    ev.id.numid = ctl->info->id.numid;
+    if (ioctl(ctl->mixer->fd, SNDRV_CTL_IOCTL_ELEM_WRITE, &ev) < 0)
+        return -1;
+    return 0;
+}
+
+int mixer_ctl_set_enum_by_name(struct mixer_ctl *ctl, const char *string)
+{
+    unsigned int n, max;
+    struct snd_ctl_elem_value ev;
+    
+    if (ctl->info->type != SNDRV_CTL_ELEM_TYPE_ENUMERATED) {
+        errno = EINVAL;
+        return -1;
+    }
+    
+    max = ctl->info->value.enumerated.items;
+    for (n = 0; n < max; n++) {
+        if (!strcmp(string, ctl->ename[n])) {
+            memset(&ev, 0, sizeof(ev));
+            ev.value.enumerated.item[0] = n;
+            ev.id.numid = ctl->info->id.numid;
+            if (ioctl(ctl->mixer->fd, SNDRV_CTL_IOCTL_ELEM_WRITE, &ev) < 0)
+                return -1;
+            return 0;
+        }
+    }
+    
+    errno = EINVAL;
+    return -1;
+}
diff --git a/pcm.c b/pcm.c
new file mode 100644
index 0000000..71849a7
--- /dev/null
+++ b/pcm.c
@@ -0,0 +1,351 @@
+/* pcm.c
+**
+** Copyright 2011, The Android Open Source Project
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of The Android Open Source Project nor the names of
+**       its contributors may be used to endorse or promote products derived
+**       from this software without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED BY The Android Open Source Project ``AS IS'' AND
+** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+** ARE DISCLAIMED. IN NO EVENT SHALL The Android Open Source Project BE LIABLE
+** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+** DAMAGE.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+
+#include <linux/ioctl.h>
+#define __force
+#define __bitwise
+#define __user
+#include <sound/asound.h>
+
+#include <tinyalsa/asoundlib.h>
+
+#define PARAM_MAX SNDRV_PCM_HW_PARAM_LAST_INTERVAL
+
+static inline int param_is_mask(int p)
+{
+    return (p >= SNDRV_PCM_HW_PARAM_FIRST_MASK) &&
+        (p <= SNDRV_PCM_HW_PARAM_LAST_MASK);
+}
+
+static inline int param_is_interval(int p)
+{
+    return (p >= SNDRV_PCM_HW_PARAM_FIRST_INTERVAL) &&
+        (p <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL);
+}
+
+static inline struct snd_interval *param_to_interval(struct snd_pcm_hw_params *p, int n)
+{
+    return &(p->intervals[n - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL]);
+}
+
+static inline struct snd_mask *param_to_mask(struct snd_pcm_hw_params *p, int n)
+{
+    return &(p->masks[n - SNDRV_PCM_HW_PARAM_FIRST_MASK]);
+}
+
+static void param_set_mask(struct snd_pcm_hw_params *p, int n, unsigned int bit)
+{
+    if (bit >= SNDRV_MASK_MAX)
+        return;
+    if (param_is_mask(n)) {
+        struct snd_mask *m = param_to_mask(p, n);
+        m->bits[0] = 0;
+        m->bits[1] = 0;
+        m->bits[bit >> 5] |= (1 << (bit & 31));
+    }
+}
+
+static void param_set_min(struct snd_pcm_hw_params *p, int n, unsigned int val)
+{
+    if (param_is_interval(n)) {
+        struct snd_interval *i = param_to_interval(p, n);
+        i->min = val;
+    }
+}
+
+static void param_set_max(struct snd_pcm_hw_params *p, int n, unsigned int val)
+{
+    if (param_is_interval(n)) {
+        struct snd_interval *i = param_to_interval(p, n);
+        i->max = val;
+    }
+}
+
+static void param_set_int(struct snd_pcm_hw_params *p, int n, unsigned int val)
+{
+    if (param_is_interval(n)) {
+        struct snd_interval *i = param_to_interval(p, n);
+        i->min = val;
+        i->max = val;
+        i->integer = 1;
+    }
+}
+
+static void param_init(struct snd_pcm_hw_params *p)
+{
+    int n;
+    memset(p, 0, sizeof(*p));
+    for (n = SNDRV_PCM_HW_PARAM_FIRST_MASK;
+         n <= SNDRV_PCM_HW_PARAM_LAST_MASK; n++) {
+            struct snd_mask *m = param_to_mask(p, n);
+            m->bits[0] = ~0;
+            m->bits[1] = ~0;
+    }
+    for (n = SNDRV_PCM_HW_PARAM_FIRST_INTERVAL;
+         n <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL; n++) {
+            struct snd_interval *i = param_to_interval(p, n);
+            i->min = 0;
+            i->max = ~0;
+    }
+}
+
+#define PCM_ERROR_MAX 128
+
+struct pcm {
+    int fd;
+    unsigned int flags;
+    int running:1;
+    int underruns;
+    unsigned int buffer_size;
+    char error[PCM_ERROR_MAX];
+    struct pcm_config config;
+};
+
+unsigned int pcm_buffer_size(struct pcm *pcm)
+{
+    return pcm->buffer_size;
+}
+
+const char* pcm_get_error(struct pcm *pcm)
+{
+    return pcm->error;
+}
+
+static int oops(struct pcm *pcm, int e, const char *fmt, ...)
+{
+    va_list ap;
+    int sz;
+
+    va_start(ap, fmt);
+    vsnprintf(pcm->error, PCM_ERROR_MAX, fmt, ap);
+    va_end(ap);
+    sz = strlen(pcm->error);
+
+    if (errno)
+        snprintf(pcm->error + sz, PCM_ERROR_MAX - sz,
+                 ": %s", strerror(e));
+    return -1;
+}
+
+int pcm_write(struct pcm *pcm, void *data, unsigned int count)
+{
+    struct snd_xferi x;
+
+    if (pcm->flags & PCM_IN)
+        return -EINVAL;
+
+    x.buf = data;
+    x.frames = count / (pcm->config.channels * 2); /* TODO: handle 32bit */
+
+    for (;;) {
+        if (!pcm->running) {
+            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_PREPARE))
+                return oops(pcm, errno, "cannot prepare channel");
+            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &x))
+                return oops(pcm, errno, "cannot write initial data");
+            pcm->running = 1;
+            return 0;
+        }
+        if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &x)) {
+            pcm->running = 0;
+            if (errno == EPIPE) {
+                    /* we failed to make our window -- try to restart */
+                pcm->underruns++;
+                continue;
+            }
+            return oops(pcm, errno, "cannot write stream data");
+        }
+        return 0;
+    }
+}
+
+int pcm_read(struct pcm *pcm, void *data, unsigned int count)
+{
+    struct snd_xferi x;
+
+    if (!(pcm->flags & PCM_IN))
+        return -EINVAL;
+
+    x.buf = data;
+    x.frames = count / (pcm->config.channels * 2); /* TODO: handle 32bit */
+
+    for (;;) {
+        if (!pcm->running) {
+            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_PREPARE))
+                return oops(pcm, errno, "cannot prepare channel");
+            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_START))
+                return oops(pcm, errno, "cannot start channel");
+            pcm->running = 1;
+        }
+        if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_READI_FRAMES, &x)) {
+            pcm->running = 0;
+            if (errno == EPIPE) {
+                    /* we failed to make our window -- try to restart */
+                pcm->underruns++;
+                continue;
+            }
+            return oops(pcm, errno, "cannot read stream data");
+        }
+        return 0;
+    }
+}
+
+static struct pcm bad_pcm = {
+    .fd = -1,
+};
+
+int pcm_close(struct pcm *pcm)
+{
+    if (pcm == &bad_pcm)
+        return 0;
+
+    if (pcm->fd >= 0)
+        close(pcm->fd);
+    pcm->running = 0;
+    pcm->buffer_size = 0;
+    pcm->fd = -1;
+    return 0;
+}
+
+static unsigned int pcm_format_to_alsa(enum pcm_format format)
+{
+    switch (format) {
+    case PCM_FORMAT_S32_LE:
+        return SNDRV_PCM_FORMAT_S32_LE;
+    default:
+    case PCM_FORMAT_S16_LE:
+        return SNDRV_PCM_FORMAT_S16_LE;
+    };
+}
+
+static unsigned int pcm_format_to_bits(enum pcm_format format)
+{
+    switch (format) {
+    case PCM_FORMAT_S32_LE:
+        return 32;
+    default:
+    case PCM_FORMAT_S16_LE:
+        return 16;
+    };
+}
+
+struct pcm *pcm_open(unsigned int device, unsigned int flags, struct pcm_config *config)
+{
+    const char *dname;
+    struct pcm *pcm;
+    struct snd_pcm_info info;
+    struct snd_pcm_hw_params params;
+    struct snd_pcm_sw_params sparams;
+
+    pcm = calloc(1, sizeof(struct pcm));
+    if (!pcm || !config)
+        return &bad_pcm; /* TODO: could support default config here */
+
+    pcm->config = *config;
+
+    if (flags & PCM_IN) {
+        dname = "/dev/snd/pcmC0D0c";
+    } else {
+        dname = "/dev/snd/pcmC0D0p";
+    }
+
+    pcm->flags = flags;
+    pcm->fd = open(dname, O_RDWR);
+    if (pcm->fd < 0) {
+        oops(pcm, errno, "cannot open device '%s'");
+        return pcm;
+    }
+
+    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_INFO, &info)) {
+        oops(pcm, errno, "cannot get info - %s");
+        goto fail;
+    }
+
+    param_init(&params);
+    param_set_mask(&params, SNDRV_PCM_HW_PARAM_ACCESS,
+                   SNDRV_PCM_ACCESS_RW_INTERLEAVED);
+    param_set_mask(&params, SNDRV_PCM_HW_PARAM_FORMAT,
+                   pcm_format_to_alsa(config->format));
+    param_set_mask(&params, SNDRV_PCM_HW_PARAM_SUBFORMAT,
+                   SNDRV_PCM_SUBFORMAT_STD);
+    param_set_min(&params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, config->period_size);
+    param_set_int(&params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS,
+                  pcm_format_to_bits(config->format));
+    param_set_int(&params, SNDRV_PCM_HW_PARAM_FRAME_BITS,
+                  pcm_format_to_bits(config->format) * config->channels);
+    param_set_int(&params, SNDRV_PCM_HW_PARAM_CHANNELS,
+                  config->channels);
+    param_set_int(&params, SNDRV_PCM_HW_PARAM_PERIODS, config->period_count);
+    param_set_int(&params, SNDRV_PCM_HW_PARAM_RATE, config->rate);
+
+    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_HW_PARAMS, &params)) {
+        oops(pcm, errno, "cannot set hw params");
+        goto fail;
+    }
+
+    memset(&sparams, 0, sizeof(sparams));
+    sparams.tstamp_mode = SNDRV_PCM_TSTAMP_NONE;
+    sparams.period_step = 1;
+    sparams.avail_min = 1;
+    sparams.start_threshold = config->period_count * config->period_size;
+    sparams.stop_threshold = config->period_count * config->period_size;
+    sparams.xfer_align = config->period_size / 2; /* needed for old kernels */
+    sparams.silence_size = 0;
+    sparams.silence_threshold = 0;
+
+    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_SW_PARAMS, &sparams)) {
+        oops(pcm, errno, "cannot set sw params");
+        goto fail;
+    }
+
+    pcm->buffer_size = config->period_count * config->period_size;
+    pcm->underruns = 0;
+    return pcm;
+
+fail:
+    close(pcm->fd);
+    pcm->fd = -1;
+    return pcm;
+}
+
+int pcm_is_ready(struct pcm *pcm)
+{
+    return pcm->fd >= 0;
+}