Introduce the operators required for the operation of substreams.
Signed-off-by: Anton Yakovlev <anton.yakovlev at opensynergy.com>
---
sound/virtio/Makefile | 3 +-
sound/virtio/virtio_pcm.c | 5 +-
sound/virtio/virtio_pcm.h | 2 +
sound/virtio/virtio_pcm_ops.c | 513 ++++++++++++++++++++++++++++++++++
4 files changed, 521 insertions(+), 2 deletions(-)
create mode 100644 sound/virtio/virtio_pcm_ops.c
diff --git a/sound/virtio/Makefile b/sound/virtio/Makefile
index 626af3cc3ed7..34493226793f 100644
--- a/sound/virtio/Makefile
+++ b/sound/virtio/Makefile
@@ -6,5 +6,6 @@ virtio_snd-objs := \
virtio_card.o \
virtio_ctl_msg.o \
virtio_pcm.o \
- virtio_pcm_msg.o
+ virtio_pcm_msg.o \
+ virtio_pcm_ops.o
diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c
index 1ab50dcc88c8..6a1ca6b2c3ca 100644
--- a/sound/virtio/virtio_pcm.c
+++ b/sound/virtio/virtio_pcm.c
@@ -121,7 +121,8 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream
*substream,
SNDRV_PCM_INFO_MMAP_VALID |
SNDRV_PCM_INFO_BATCH |
SNDRV_PCM_INFO_BLOCK_TRANSFER |
- SNDRV_PCM_INFO_INTERLEAVED;
+ SNDRV_PCM_INFO_INTERLEAVED |
+ SNDRV_PCM_INFO_PAUSE;
if (!info->channels_min || info->channels_min >
info->channels_max) {
dev_err(&vdev->dev,
@@ -503,6 +504,8 @@ int virtsnd_pcm_build_devs(struct virtio_snd *snd)
if (rc)
return rc;
}
+
+ snd_pcm_set_ops(pcm->pcm, i, &virtsnd_pcm_ops);
}
return 0;
diff --git a/sound/virtio/virtio_pcm.h b/sound/virtio/virtio_pcm.h
index d011b7e1d18d..fe467bc05d8b 100644
--- a/sound/virtio/virtio_pcm.h
+++ b/sound/virtio/virtio_pcm.h
@@ -90,6 +90,8 @@ struct virtio_pcm {
struct virtio_pcm_stream streams[SNDRV_PCM_STREAM_LAST + 1];
};
+extern const struct snd_pcm_ops virtsnd_pcm_ops;
+
int virtsnd_pcm_validate(struct virtio_device *vdev);
int virtsnd_pcm_parse_cfg(struct virtio_snd *snd);
diff --git a/sound/virtio/virtio_pcm_ops.c b/sound/virtio/virtio_pcm_ops.c
new file mode 100644
index 000000000000..19882777fcd6
--- /dev/null
+++ b/sound/virtio/virtio_pcm_ops.c
@@ -0,0 +1,513 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Sound card driver for virtio
+ * Copyright (C) 2020 OpenSynergy GmbH
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+#include <sound/pcm_params.h>
+
+#include "virtio_card.h"
+
+/*
+ * Our main concern here is maintaining the correct state of the underlying I/O
+ * virtqueues. Thus, operators are implemented to support all of the following
+ * possible control paths (excluding all trivial ones):
+ *
+ * +---------+
+ * | open() |<------------------+
+ * +----+----+ |
+ * v |
+ * +------+------+ |
+ * +------------->| hw_params() |<-------------+ |
+ * | +-------------+ | |
+ * | v | |
+ * | +-----------+ | |
+ * | | prepare() |<-----------+ | |
+ * | +-----------+ | | |
+ * | v | | |
+ * | +-------------------------+ | | |
+ * +-----------+ | trigger(START/ | | | |
+ * | restore() | | PAUSE_RELEASE/ |<-+ | | |
+ * +-----------+ | RESUME) | | | | |
+ * ^ +-------------------------+ | | | |
+ * | v | | | |
+ * | +-----------+ | | | |
+ * | | pointer() | | | | |
+ * | +-----------+ | | | |
+ * | v | | | |
+ * | +---------------------+ | | | |
+ * +-----------+ | trigger(STOP/ |----+ | | |
+ * | freeze() |<---| PAUSE_PUSH/ |-------+ | |
+ * +-----------+ | SUSPEND) | | |
+ * +---------------------+ | |
+ * v | |
+ * +-----------+ | |
+ * | hw_free() |---------------+ |
+ * +-----------+ |
+ * v |
+ * +---------+ |
+ * | close() |-------------------+
+ * +---------+
+ */
+
+/* Map for converting ALSA format to VirtIO format. */
+struct virtsnd_a2v_format {
+ unsigned int alsa_bit;
+ unsigned int vio_bit;
+};
+
+static const struct virtsnd_a2v_format g_a2v_format_map[] = {
+ { SNDRV_PCM_FORMAT_IMA_ADPCM, VIRTIO_SND_PCM_FMT_IMA_ADPCM },
+ { SNDRV_PCM_FORMAT_MU_LAW, VIRTIO_SND_PCM_FMT_MU_LAW },
+ { SNDRV_PCM_FORMAT_A_LAW, VIRTIO_SND_PCM_FMT_A_LAW },
+ { SNDRV_PCM_FORMAT_S8, VIRTIO_SND_PCM_FMT_S8 },
+ { SNDRV_PCM_FORMAT_U8, VIRTIO_SND_PCM_FMT_U8 },
+ { SNDRV_PCM_FORMAT_S16_LE, VIRTIO_SND_PCM_FMT_S16 },
+ { SNDRV_PCM_FORMAT_U16_LE, VIRTIO_SND_PCM_FMT_U16 },
+ { SNDRV_PCM_FORMAT_S18_3LE, VIRTIO_SND_PCM_FMT_S18_3 },
+ { SNDRV_PCM_FORMAT_U18_3LE, VIRTIO_SND_PCM_FMT_U18_3 },
+ { SNDRV_PCM_FORMAT_S20_3LE, VIRTIO_SND_PCM_FMT_S20_3 },
+ { SNDRV_PCM_FORMAT_U20_3LE, VIRTIO_SND_PCM_FMT_U20_3 },
+ { SNDRV_PCM_FORMAT_S24_3LE, VIRTIO_SND_PCM_FMT_S24_3 },
+ { SNDRV_PCM_FORMAT_U24_3LE, VIRTIO_SND_PCM_FMT_U24_3 },
+ { SNDRV_PCM_FORMAT_S20_LE, VIRTIO_SND_PCM_FMT_S20 },
+ { SNDRV_PCM_FORMAT_U20_LE, VIRTIO_SND_PCM_FMT_U20 },
+ { SNDRV_PCM_FORMAT_S24_LE, VIRTIO_SND_PCM_FMT_S24 },
+ { SNDRV_PCM_FORMAT_U24_LE, VIRTIO_SND_PCM_FMT_U24 },
+ { SNDRV_PCM_FORMAT_S32_LE, VIRTIO_SND_PCM_FMT_S32 },
+ { SNDRV_PCM_FORMAT_U32_LE, VIRTIO_SND_PCM_FMT_U32 },
+ { SNDRV_PCM_FORMAT_FLOAT_LE, VIRTIO_SND_PCM_FMT_FLOAT },
+ { SNDRV_PCM_FORMAT_FLOAT64_LE, VIRTIO_SND_PCM_FMT_FLOAT64 },
+ { SNDRV_PCM_FORMAT_DSD_U8, VIRTIO_SND_PCM_FMT_DSD_U8 },
+ { SNDRV_PCM_FORMAT_DSD_U16_LE, VIRTIO_SND_PCM_FMT_DSD_U16 },
+ { SNDRV_PCM_FORMAT_DSD_U32_LE, VIRTIO_SND_PCM_FMT_DSD_U32 },
+ { SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE,
+ VIRTIO_SND_PCM_FMT_IEC958_SUBFRAME }
+};
+
+/* Map for converting ALSA frame rate to VirtIO frame rate. */
+struct virtsnd_a2v_rate {
+ unsigned int rate;
+ unsigned int vio_bit;
+};
+
+static const struct virtsnd_a2v_rate g_a2v_rate_map[] = {
+ { 5512, VIRTIO_SND_PCM_RATE_5512 },
+ { 8000, VIRTIO_SND_PCM_RATE_8000 },
+ { 11025, VIRTIO_SND_PCM_RATE_11025 },
+ { 16000, VIRTIO_SND_PCM_RATE_16000 },
+ { 22050, VIRTIO_SND_PCM_RATE_22050 },
+ { 32000, VIRTIO_SND_PCM_RATE_32000 },
+ { 44100, VIRTIO_SND_PCM_RATE_44100 },
+ { 48000, VIRTIO_SND_PCM_RATE_48000 },
+ { 64000, VIRTIO_SND_PCM_RATE_64000 },
+ { 88200, VIRTIO_SND_PCM_RATE_88200 },
+ { 96000, VIRTIO_SND_PCM_RATE_96000 },
+ { 176400, VIRTIO_SND_PCM_RATE_176400 },
+ { 192000, VIRTIO_SND_PCM_RATE_192000 }
+};
+
+/**
+ * virtsnd_pcm_release() - Release the PCM substream on the device side.
+ * @substream: VirtIO substream.
+ *
+ * Context: Any context that permits to sleep.
+ * Return: 0 on success, -errno on failure.
+ */
+static inline bool virtsnd_pcm_released(struct virtio_pcm_substream *substream)
+{
+ /*
+ * The spec states that upon receipt of the RELEASE command "the device
+ * MUST complete all pending I/O messages for the specified stream ID".
+ * Thus, we consider the absence of I/O messages in the queue as an
+ * indication that the substream has been released.
+ */
+ return atomic_read(&substream->msg_count) == 0;
+}
+
+static int virtsnd_pcm_release(struct virtio_pcm_substream *substream)
+{
+ struct virtio_snd *snd = substream->snd;
+ struct virtio_snd_msg *msg;
+ unsigned int js = msecs_to_jiffies(msg_timeout_ms);
+ int rc;
+
+ msg = virtsnd_pcm_ctl_msg_alloc(substream, VIRTIO_SND_R_PCM_RELEASE,
+ GFP_KERNEL);
+ if (IS_ERR(msg))
+ return PTR_ERR(msg);
+
+ rc = virtsnd_ctl_msg_send_sync(snd, msg);
+ if (rc)
+ return rc;
+
+ return wait_event_interruptible_timeout(substream->msg_empty,
+ virtsnd_pcm_released(substream),
+ js);
+}
+
+/**
+ * virtsnd_pcm_open() - Open the PCM substream.
+ * @substream: Kernel ALSA substream.
+ *
+ * Context: Any context.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_pcm_open(struct snd_pcm_substream *substream)
+{
+ struct virtio_pcm *pcm = snd_pcm_substream_chip(substream);
+ struct virtio_pcm_substream *ss = NULL;
+
+ if (pcm) {
+ switch (substream->stream) {
+ case SNDRV_PCM_STREAM_PLAYBACK:
+ case SNDRV_PCM_STREAM_CAPTURE: {
+ struct virtio_pcm_stream *stream +
&pcm->streams[substream->stream];
+
+ if (substream->number < stream->nsubstreams)
+ ss = stream->substreams[substream->number];
+ break;
+ }
+ }
+ }
+
+ if (!ss)
+ return -EBADFD;
+
+ substream->runtime->hw = ss->hw;
+ substream->private_data = ss;
+
+ return 0;
+}
+
+/**
+ * virtsnd_pcm_close() - Close the PCM substream.
+ * @substream: Kernel ALSA substream.
+ *
+ * Context: Any context.
+ * Return: 0.
+ */
+static int virtsnd_pcm_close(struct snd_pcm_substream *substream)
+{
+ return 0;
+}
+
+/**
+ * virtsnd_pcm_hw_params() - Set the parameters of the PCM substream.
+ * @substream: Kernel ALSA substream.
+ * @hw_params: Hardware parameters (can be NULL).
+ *
+ * The function can be called both from the upper level (in this case,
+ * @hw_params is not NULL) or from the driver itself (in this case, @hw_params
+ * is NULL, and the parameter values are taken from the runtime structure).
+ *
+ * In all cases, the function:
+ * 1. checks the state of the virtqueue and, if necessary, tries to fix it,
+ * 2. sets the parameters on the device side,
+ * 3. allocates a hardware buffer and I/O messages.
+ *
+ * Context: Any context that permits to sleep.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_pcm_hw_params(struct snd_pcm_substream *substream,
+ struct snd_pcm_hw_params *hw_params)
+{
+ struct snd_pcm_runtime *runtime = substream->runtime;
+ struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream);
+ struct virtio_device *vdev = ss->snd->vdev;
+ struct virtio_snd_msg *msg;
+ struct virtio_snd_pcm_set_params *request;
+ snd_pcm_format_t format;
+ unsigned int channels;
+ unsigned int rate;
+ unsigned int buffer_bytes;
+ unsigned int period_bytes;
+ unsigned int periods;
+ unsigned int i;
+ int vformat = -1;
+ int vrate = -1;
+ int rc;
+
+ /*
+ * If we got here after ops->trigger() was called, the queue may
+ * still contain messages. In this case, we need to release the
+ * substream first.
+ */
+ if (atomic_read(&ss->msg_count)) {
+ rc = virtsnd_pcm_release(ss);
+ if (rc) {
+ dev_err(&vdev->dev,
+ "SID %u: invalid I/O queue state\n",
+ ss->sid);
+ return rc;
+ }
+ }
+
+ /* Set hardware parameters in device */
+ if (hw_params) {
+ format = params_format(hw_params);
+ channels = params_channels(hw_params);
+ rate = params_rate(hw_params);
+ buffer_bytes = params_buffer_bytes(hw_params);
+ period_bytes = params_period_bytes(hw_params);
+ periods = params_periods(hw_params);
+ } else {
+ format = runtime->format;
+ channels = runtime->channels;
+ rate = runtime->rate;
+ buffer_bytes = frames_to_bytes(runtime, runtime->buffer_size);
+ period_bytes = frames_to_bytes(runtime, runtime->period_size);
+ periods = runtime->periods;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(g_a2v_format_map); ++i)
+ if (g_a2v_format_map[i].alsa_bit == format) {
+ vformat = g_a2v_format_map[i].vio_bit;
+
+ break;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(g_a2v_rate_map); ++i)
+ if (g_a2v_rate_map[i].rate == rate) {
+ vrate = g_a2v_rate_map[i].vio_bit;
+
+ break;
+ }
+
+ if (vformat == -1 || vrate == -1)
+ return -EINVAL;
+
+ msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_SET_PARAMS,
+ GFP_KERNEL);
+ if (IS_ERR(msg))
+ return PTR_ERR(msg);
+
+ request = sg_virt(&msg->sg_request);
+
+ request->buffer_bytes = cpu_to_virtio32(vdev, buffer_bytes);
+ request->period_bytes = cpu_to_virtio32(vdev, period_bytes);
+ request->channels = channels;
+ request->format = vformat;
+ request->rate = vrate;
+
+ if (ss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING))
+ request->features |+ cpu_to_virtio32(vdev,
+ 1U << VIRTIO_SND_PCM_F_MSG_POLLING);
+
+ if (ss->features & (1U << VIRTIO_SND_PCM_F_EVT_XRUNS))
+ request->features |+ cpu_to_virtio32(vdev,
+ 1U << VIRTIO_SND_PCM_F_EVT_XRUNS);
+
+ rc = virtsnd_ctl_msg_send_sync(ss->snd, msg);
+ if (rc)
+ return rc;
+
+ /* If the buffer was already allocated earlier, do nothing. */
+ if (runtime->dma_area)
+ return 0;
+
+ /* Allocate hardware buffer */
+ rc = snd_pcm_lib_malloc_pages(substream, buffer_bytes);
+ if (rc < 0)
+ return rc;
+
+ /* Allocate and initialize I/O messages */
+ rc = virtsnd_pcm_msg_alloc(ss, periods, runtime->dma_area,
+ period_bytes);
+ if (rc)
+ snd_pcm_lib_free_pages(substream);
+
+ return rc;
+}
+
+/**
+ * virtsnd_pcm_hw_free() - Reset the parameters of the PCM substream.
+ * @substream: Kernel ALSA substream.
+ *
+ * The function does the following:
+ * 1. tries to release the PCM substream on the device side,
+ * 2. frees the hardware buffer.
+ *
+ * Context: Any context that permits to sleep.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_pcm_hw_free(struct snd_pcm_substream *substream)
+{
+ struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream);
+ int rc;
+
+ rc = virtsnd_pcm_release(ss);
+
+ /*
+ * Even if we failed to send the RELEASE message or wait for the queue
+ * flush to complete, we can safely delete the buffer. Because after
+ * receiving the STOP command, the device must stop all I/O message
+ * processing. If there are still pending messages in the queue, the
+ * next ops->hw_params() call should deal with this.
+ */
+ snd_pcm_lib_free_pages(substream);
+
+ return rc;
+}
+
+/**
+ * virtsnd_pcm_hw_params() - Prepare the PCM substream.
+ * @substream: Kernel ALSA substream.
+ *
+ * The function can be called both from the upper level or from the driver
+ * itself.
+ *
+ * In all cases, the function:
+ * 1. checks the state of the virtqueue and, if necessary, tries to fix it,
+ * 2. prepares the substream on the device side.
+ *
+ * Context: Any context that permits to sleep. May take and release the tx/rx
+ * queue spinlock.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream)
+{
+ struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream);
+ struct virtio_snd_queue *queue = virtsnd_pcm_queue(ss);
+ struct virtio_snd_msg *msg;
+ unsigned long flags;
+ int rc;
+
+ /*
+ * If we got here after ops->trigger() was called, the queue may
+ * still contain messages. In this case, we need to reset the
+ * substream first.
+ */
+ if (atomic_read(&ss->msg_count)) {
+ rc = virtsnd_pcm_hw_params(substream, NULL);
+ if (rc)
+ return rc;
+ }
+
+ spin_lock_irqsave(&queue->lock, flags);
+ ss->msg_last_enqueued = -1;
+ spin_unlock_irqrestore(&queue->lock, flags);
+
+ /*
+ * Since I/O messages are asynchronous, they can be completed
+ * when the runtime structure no longer exists. Since each
+ * completion implies incrementing the hw_ptr, we cache all the
+ * current values needed to compute the new hw_ptr value.
+ */
+ ss->frame_bytes = substream->runtime->frame_bits >> 3;
+ ss->period_size = substream->runtime->period_size;
+ ss->buffer_size = substream->runtime->buffer_size;
+
+ atomic_set(&ss->hw_ptr, 0);
+ atomic_set(&ss->xfer_xrun, 0);
+ atomic_set(&ss->msg_count, 0);
+
+ msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_PREPARE,
+ GFP_KERNEL);
+ if (IS_ERR(msg))
+ return PTR_ERR(msg);
+
+ return virtsnd_ctl_msg_send_sync(ss->snd, msg);
+}
+
+/**
+ * virtsnd_pcm_trigger() - Process command for the PCM substream.
+ * @substream: Kernel ALSA substream.
+ * @command: Substream command (SNDRV_PCM_TRIGGER_XXX).
+ *
+ * Depending on the command, the function does the following:
+ * 1. enables/disables data transmission,
+ * 2. starts/stops the substream on the device side.
+ *
+ * Context: Atomic context. May take and release the tx/rx queue spinlock.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int
command)
+{
+ struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream);
+ struct virtio_snd *snd = ss->snd;
+ struct virtio_snd_queue *queue = virtsnd_pcm_queue(ss);
+ struct virtio_snd_msg *msg;
+
+ switch (command) {
+ case SNDRV_PCM_TRIGGER_START:
+ case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: {
+ int rc;
+
+ spin_lock(&queue->lock);
+ rc = virtsnd_pcm_msg_send(ss);
+ spin_unlock(&queue->lock);
+ if (rc)
+ return rc;
+
+ atomic_set(&ss->xfer_enabled, 1);
+
+ msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_START,
+ GFP_ATOMIC);
+ if (IS_ERR(msg))
+ return PTR_ERR(msg);
+
+ return virtsnd_ctl_msg_send(snd, msg);
+ }
+ case SNDRV_PCM_TRIGGER_STOP:
+ case SNDRV_PCM_TRIGGER_PAUSE_PUSH: {
+ atomic_set(&ss->xfer_enabled, 0);
+
+ msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_STOP,
+ GFP_ATOMIC);
+ if (IS_ERR(msg))
+ return PTR_ERR(msg);
+
+ return virtsnd_ctl_msg_send(snd, msg);
+ }
+ default: {
+ return -EINVAL;
+ }
+ }
+}
+
+/**
+ * virtsnd_pcm_pointer() - Get the current hardware position for the PCM
+ * substream.
+ * @substream: Kernel ALSA substream.
+ *
+ * Context: Atomic context.
+ * Return: Hardware position in frames inside [0 ... buffer_size) range.
+ */
+static snd_pcm_uframes_t
+virtsnd_pcm_pointer(struct snd_pcm_substream *substream)
+{
+ struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream);
+
+ if (atomic_read(&ss->xfer_xrun))
+ return SNDRV_PCM_POS_XRUN;
+
+ return (snd_pcm_uframes_t)atomic_read(&ss->hw_ptr);
+}
+
+/* PCM substream operators map. */
+const struct snd_pcm_ops virtsnd_pcm_ops = {
+ .open = virtsnd_pcm_open,
+ .close = virtsnd_pcm_close,
+ .ioctl = snd_pcm_lib_ioctl,
+ .hw_params = virtsnd_pcm_hw_params,
+ .hw_free = virtsnd_pcm_hw_free,
+ .prepare = virtsnd_pcm_prepare,
+ .trigger = virtsnd_pcm_trigger,
+ .pointer = virtsnd_pcm_pointer,
+};
--
2.30.0
Guennadi Liakhovetski
2021-Jan-25 16:59 UTC
[PATCH v2 6/9] ALSA: virtio: PCM substream operators
On Sun, 24 Jan 2021, Anton Yakovlev wrote:> Introduce the operators required for the operation of substreams. > > Signed-off-by: Anton Yakovlev <anton.yakovlev at opensynergy.com> > --- > sound/virtio/Makefile | 3 +- > sound/virtio/virtio_pcm.c | 5 +- > sound/virtio/virtio_pcm.h | 2 + > sound/virtio/virtio_pcm_ops.c | 513 ++++++++++++++++++++++++++++++++++ > 4 files changed, 521 insertions(+), 2 deletions(-) > create mode 100644 sound/virtio/virtio_pcm_ops.c[snip]> diff --git a/sound/virtio/virtio_pcm_ops.c b/sound/virtio/virtio_pcm_ops.c > new file mode 100644 > index 000000000000..19882777fcd6 > --- /dev/null > +++ b/sound/virtio/virtio_pcm_ops.c > @@ -0,0 +1,513 @@[snip]> +/** > + * virtsnd_pcm_release() - Release the PCM substream on the device side. > + * @substream: VirtIO substream. > + * > + * Context: Any context that permits to sleep. > + * Return: 0 on success, -errno on failure. > + */ > +static inline bool virtsnd_pcm_released(struct virtio_pcm_substream *substream) > +{ > + /* > + * The spec states that upon receipt of the RELEASE command "the device > + * MUST complete all pending I/O messages for the specified stream ID". > + * Thus, we consider the absence of I/O messages in the queue as an > + * indication that the substream has been released. > + */ > + return atomic_read(&substream->msg_count) == 0;Also here having it atomic doesn't really seem to help. This just means, that at some point of time it was == 0.> +} > + > +static int virtsnd_pcm_release(struct virtio_pcm_substream *substream)kernel-doc missing> +{ > + struct virtio_snd *snd = substream->snd; > + struct virtio_snd_msg *msg; > + unsigned int js = msecs_to_jiffies(msg_timeout_ms); > + int rc; > + > + msg = virtsnd_pcm_ctl_msg_alloc(substream, VIRTIO_SND_R_PCM_RELEASE, > + GFP_KERNEL); > + if (IS_ERR(msg)) > + return PTR_ERR(msg); > + > + rc = virtsnd_ctl_msg_send_sync(snd, msg); > + if (rc) > + return rc; > + > + return wait_event_interruptible_timeout(substream->msg_empty, > + virtsnd_pcm_released(substream), > + js); > +} > + > +/** > + * virtsnd_pcm_open() - Open the PCM substream. > + * @substream: Kernel ALSA substream. > + * > + * Context: Any context. > + * Return: 0 on success, -errno on failure. > + */ > +static int virtsnd_pcm_open(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm *pcm = snd_pcm_substream_chip(substream); > + struct virtio_pcm_substream *ss = NULL; > + > + if (pcm) { > + switch (substream->stream) { > + case SNDRV_PCM_STREAM_PLAYBACK: > + case SNDRV_PCM_STREAM_CAPTURE: { > + struct virtio_pcm_stream *stream > + &pcm->streams[substream->stream]; > + > + if (substream->number < stream->nsubstreams)Can this condition ever be false?> + ss = stream->substreams[substream->number]; > + break; > + } > + } > + } > + > + if (!ss) > + return -EBADFD; > + > + substream->runtime->hw = ss->hw; > + substream->private_data = ss; > + > + return 0; > +} > + > +/** > + * virtsnd_pcm_close() - Close the PCM substream. > + * @substream: Kernel ALSA substream. > + * > + * Context: Any context. > + * Return: 0. > + */ > +static int virtsnd_pcm_close(struct snd_pcm_substream *substream) > +{ > + return 0; > +} > + > +/** > + * virtsnd_pcm_hw_params() - Set the parameters of the PCM substream. > + * @substream: Kernel ALSA substream. > + * @hw_params: Hardware parameters (can be NULL). > + * > + * The function can be called both from the upper level (in this case, > + * @hw_params is not NULL) or from the driver itself (in this case, @hw_params > + * is NULL, and the parameter values are taken from the runtime structure). > + * > + * In all cases, the function: > + * 1. checks the state of the virtqueue and, if necessary, tries to fix it, > + * 2. sets the parameters on the device side, > + * 3. allocates a hardware buffer and I/O messages. > + * > + * Context: Any context that permits to sleep. > + * Return: 0 on success, -errno on failure. > + */ > +static int virtsnd_pcm_hw_params(struct snd_pcm_substream *substream, > + struct snd_pcm_hw_params *hw_params) > +{ > + struct snd_pcm_runtime *runtime = substream->runtime; > + struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream); > + struct virtio_device *vdev = ss->snd->vdev; > + struct virtio_snd_msg *msg; > + struct virtio_snd_pcm_set_params *request; > + snd_pcm_format_t format; > + unsigned int channels; > + unsigned int rate; > + unsigned int buffer_bytes; > + unsigned int period_bytes; > + unsigned int periods; > + unsigned int i; > + int vformat = -1; > + int vrate = -1; > + int rc; > + > + /* > + * If we got here after ops->trigger() was called, the queue may > + * still contain messages. In this case, we need to release the > + * substream first. > + */ > + if (atomic_read(&ss->msg_count)) { > + rc = virtsnd_pcm_release(ss); > + if (rc) { > + dev_err(&vdev->dev, > + "SID %u: invalid I/O queue state\n", > + ss->sid); > + return rc; > + } > + } > + > + /* Set hardware parameters in device */ > + if (hw_params) { > + format = params_format(hw_params); > + channels = params_channels(hw_params); > + rate = params_rate(hw_params); > + buffer_bytes = params_buffer_bytes(hw_params); > + period_bytes = params_period_bytes(hw_params); > + periods = params_periods(hw_params); > + } else { > + format = runtime->format; > + channels = runtime->channels; > + rate = runtime->rate; > + buffer_bytes = frames_to_bytes(runtime, runtime->buffer_size); > + period_bytes = frames_to_bytes(runtime, runtime->period_size); > + periods = runtime->periods; > + } > + > + for (i = 0; i < ARRAY_SIZE(g_a2v_format_map); ++i) > + if (g_a2v_format_map[i].alsa_bit == format) { > + vformat = g_a2v_format_map[i].vio_bit; > + > + break; > + } > + > + for (i = 0; i < ARRAY_SIZE(g_a2v_rate_map); ++i) > + if (g_a2v_rate_map[i].rate == rate) { > + vrate = g_a2v_rate_map[i].vio_bit; > + > + break; > + } > + > + if (vformat == -1 || vrate == -1) > + return -EINVAL; > + > + msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_SET_PARAMS, > + GFP_KERNEL); > + if (IS_ERR(msg)) > + return PTR_ERR(msg); > + > + request = sg_virt(&msg->sg_request); > + > + request->buffer_bytes = cpu_to_virtio32(vdev, buffer_bytes); > + request->period_bytes = cpu_to_virtio32(vdev, period_bytes); > + request->channels = channels; > + request->format = vformat; > + request->rate = vrate;I presume the latter three fields don't have to be endienness-converted, perhaps they're 8-bit wide only.> + > + if (ss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING)) > + request->features |> + cpu_to_virtio32(vdev, > + 1U << VIRTIO_SND_PCM_F_MSG_POLLING); > + > + if (ss->features & (1U << VIRTIO_SND_PCM_F_EVT_XRUNS)) > + request->features |> + cpu_to_virtio32(vdev, > + 1U << VIRTIO_SND_PCM_F_EVT_XRUNS); > + > + rc = virtsnd_ctl_msg_send_sync(ss->snd, msg);Wouldn't it be better to only try to send the message after below allocations completed successfully?> + if (rc) > + return rc; > + > + /* If the buffer was already allocated earlier, do nothing. */ > + if (runtime->dma_area) > + return 0; > + > + /* Allocate hardware buffer */ > + rc = snd_pcm_lib_malloc_pages(substream, buffer_bytes); > + if (rc < 0) > + return rc; > + > + /* Allocate and initialize I/O messages */ > + rc = virtsnd_pcm_msg_alloc(ss, periods, runtime->dma_area, > + period_bytes); > + if (rc) > + snd_pcm_lib_free_pages(substream); > + > + return rc; > +} > + > +/** > + * virtsnd_pcm_hw_free() - Reset the parameters of the PCM substream. > + * @substream: Kernel ALSA substream. > + * > + * The function does the following: > + * 1. tries to release the PCM substream on the device side, > + * 2. frees the hardware buffer. > + * > + * Context: Any context that permits to sleep. > + * Return: 0 on success, -errno on failure. > + */ > +static int virtsnd_pcm_hw_free(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream); > + int rc; > + > + rc = virtsnd_pcm_release(ss); > + > + /* > + * Even if we failed to send the RELEASE message or wait for the queue > + * flush to complete, we can safely delete the buffer. Because after > + * receiving the STOP command, the device must stop all I/O message > + * processing. If there are still pending messages in the queue, the > + * next ops->hw_params() call should deal with this. > + */ > + snd_pcm_lib_free_pages(substream); > + > + return rc; > +} > + > +/** > + * virtsnd_pcm_hw_params() - Prepare the PCM substream.copy-paste: this is virtsnd_pcm_prepare()> + * @substream: Kernel ALSA substream. > + * > + * The function can be called both from the upper level or from the driver > + * itself. > + * > + * In all cases, the function: > + * 1. checks the state of the virtqueue and, if necessary, tries to fix it, > + * 2. prepares the substream on the device side. > + * > + * Context: Any context that permits to sleep. May take and release the tx/rx > + * queue spinlock. > + * Return: 0 on success, -errno on failure. > + */ > +static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream); > + struct virtio_snd_queue *queue = virtsnd_pcm_queue(ss); > + struct virtio_snd_msg *msg; > + unsigned long flags; > + int rc; > + > + /* > + * If we got here after ops->trigger() was called, the queue may > + * still contain messages. In this case, we need to reset the > + * substream first. > + */ > + if (atomic_read(&ss->msg_count)) { > + rc = virtsnd_pcm_hw_params(substream, NULL); > + if (rc) > + return rc; > + } > + > + spin_lock_irqsave(&queue->lock, flags); > + ss->msg_last_enqueued = -1; > + spin_unlock_irqrestore(&queue->lock, flags); > + > + /* > + * Since I/O messages are asynchronous, they can be completed > + * when the runtime structure no longer exists. Since each > + * completion implies incrementing the hw_ptr, we cache all the > + * current values needed to compute the new hw_ptr value. > + */ > + ss->frame_bytes = substream->runtime->frame_bits >> 3; > + ss->period_size = substream->runtime->period_size; > + ss->buffer_size = substream->runtime->buffer_size; > + > + atomic_set(&ss->hw_ptr, 0); > + atomic_set(&ss->xfer_xrun, 0); > + atomic_set(&ss->msg_count, 0); > + > + msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_PREPARE, > + GFP_KERNEL); > + if (IS_ERR(msg)) > + return PTR_ERR(msg); > + > + return virtsnd_ctl_msg_send_sync(ss->snd, msg); > +} > + > +/** > + * virtsnd_pcm_trigger() - Process command for the PCM substream. > + * @substream: Kernel ALSA substream. > + * @command: Substream command (SNDRV_PCM_TRIGGER_XXX). > + * > + * Depending on the command, the function does the following: > + * 1. enables/disables data transmission, > + * 2. starts/stops the substream on the device side. > + * > + * Context: Atomic context. May take and release the tx/rx queue spinlock.Really? Cannot .trigger() sleep? E.g. I see mdelay(25) in snd_es18xx_playback1_trigger()> + * Return: 0 on success, -errno on failure. > + */ > +static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int command) > +{ > + struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream); > + struct virtio_snd *snd = ss->snd; > + struct virtio_snd_queue *queue = virtsnd_pcm_queue(ss); > + struct virtio_snd_msg *msg; > + > + switch (command) { > + case SNDRV_PCM_TRIGGER_START: > + case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: { > + int rc; > + > + spin_lock(&queue->lock); > + rc = virtsnd_pcm_msg_send(ss); > + spin_unlock(&queue->lock);Maybe it would be good to explain why locking is required here and isn't required in most other locations, where messages are sent? Thanks Guennadi> + if (rc) > + return rc; > + > + atomic_set(&ss->xfer_enabled, 1); > + > + msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_START, > + GFP_ATOMIC); > + if (IS_ERR(msg)) > + return PTR_ERR(msg); > + > + return virtsnd_ctl_msg_send(snd, msg); > + } > + case SNDRV_PCM_TRIGGER_STOP: > + case SNDRV_PCM_TRIGGER_PAUSE_PUSH: { > + atomic_set(&ss->xfer_enabled, 0); > + > + msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_STOP, > + GFP_ATOMIC); > + if (IS_ERR(msg)) > + return PTR_ERR(msg); > + > + return virtsnd_ctl_msg_send(snd, msg); > + } > + default: { > + return -EINVAL; > + } > + } > +} > + > +/** > + * virtsnd_pcm_pointer() - Get the current hardware position for the PCM > + * substream. > + * @substream: Kernel ALSA substream. > + * > + * Context: Atomic context. > + * Return: Hardware position in frames inside [0 ... buffer_size) range. > + */ > +static snd_pcm_uframes_t > +virtsnd_pcm_pointer(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm_substream *ss = snd_pcm_substream_chip(substream); > + > + if (atomic_read(&ss->xfer_xrun)) > + return SNDRV_PCM_POS_XRUN; > + > + return (snd_pcm_uframes_t)atomic_read(&ss->hw_ptr); > +} > + > +/* PCM substream operators map. */ > +const struct snd_pcm_ops virtsnd_pcm_ops = { > + .open = virtsnd_pcm_open, > + .close = virtsnd_pcm_close, > + .ioctl = snd_pcm_lib_ioctl, > + .hw_params = virtsnd_pcm_hw_params, > + .hw_free = virtsnd_pcm_hw_free, > + .prepare = virtsnd_pcm_prepare, > + .trigger = virtsnd_pcm_trigger, > + .pointer = virtsnd_pcm_pointer, > +}; > -- > 2.30.0 > > > _______________________________________________ > Virtualization mailing list > Virtualization at lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/virtualization >
On 25.01.2021 17:59, Guennadi Liakhovetski wrote:
> On Sun, 24 Jan 2021, Anton Yakovlev wrote:
>
> [snip]
>
>> +/**
>> + * virtsnd_pcm_release() - Release the PCM substream on the device
side.
>> + * @substream: VirtIO substream.
>> + *
>> + * Context: Any context that permits to sleep.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static inline bool virtsnd_pcm_released(struct virtio_pcm_substream
>> *substream)
>> +{
>> + /*
>> + * The spec states that upon receipt of the RELEASE command
"the
>> device
>> + * MUST complete all pending I/O messages for the specified
>> stream ID".
>> + * Thus, we consider the absence of I/O messages in the queue
as an
>> + * indication that the substream has been released.
>> + */
>> + return atomic_read(&substream->msg_count) == 0;
>
> Also here having it atomic doesn't really seem to help. This just
means,
> that at some point of time it was == 0.
Technically, you're right. In practice, everything looks like this:
I/O messages are added to the virtqueue either at the start of the
substream or in the interrupt handler (and only as long as .xfer_enabled
is true). In general, this means that the .msg_count can only be
incremented in the interrupt handler. As soon as the substream stops,
the .xfer_enabled becomes false and the .msg_count no longer increases.
This means that the .msg_count was either already 0, or we need to wait
for it to become 0.
>> +}
>> +
>> +static int virtsnd_pcm_release(struct virtio_pcm_substream
*substream)
>
> kernel-doc missing
Yeap, thanks!
>> +{
>> + struct virtio_snd *snd = substream->snd;
>> + struct virtio_snd_msg *msg;
>> + unsigned int js = msecs_to_jiffies(msg_timeout_ms);
>> + int rc;
>> +
>> + msg = virtsnd_pcm_ctl_msg_alloc(substream,
>> VIRTIO_SND_R_PCM_RELEASE,
>> + GFP_KERNEL);
>> + if (IS_ERR(msg))
>> + return PTR_ERR(msg);
>> +
>> + rc = virtsnd_ctl_msg_send_sync(snd, msg);
>> + if (rc)
>> + return rc;
>> +
>> + return wait_event_interruptible_timeout(substream->msg_empty,
>> +
>> virtsnd_pcm_released(substream),
>> + js);
>
> wait_event_interruptible_timeout() will return a positive number in
> success cases, 0 means a timeout and condition still false. Whereas when
> you call this function you interpret 0 as success and you expect any != 0
> to be a negative error. Wondering how this worked during your tests?
Yeah, that's actually a bug. We haven't hit a timeout on that control
path.
>> +}
>> +
>> +/**
>> + * virtsnd_pcm_open() - Open the PCM substream.
>> + * @substream: Kernel ALSA substream.
>> + *
>> + * Context: Any context.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_pcm_open(struct snd_pcm_substream *substream)
>> +{
>> + struct virtio_pcm *pcm = snd_pcm_substream_chip(substream);
>> + struct virtio_pcm_substream *ss = NULL;
>> +
>> + if (pcm) {
>> + switch (substream->stream) {
>> + case SNDRV_PCM_STREAM_PLAYBACK:
>> + case SNDRV_PCM_STREAM_CAPTURE: {
>> + struct virtio_pcm_stream *stream >> +
&pcm->streams[substream->stream];
>> +
>> + if (substream->number <
stream->nsubstreams)
>
> Can this condition ever be false?
Hard to tell. But there may be some bug. In general, I try to adhere to
the rule that if an array element is referenced by index, it is better
to check the index value first.
>> + ss =
stream->substreams[substream->number];
>> + break;
>> + }
>> + }
>> + }
>> +
>> + if (!ss)
>> + return -EBADFD;
>> +
>> + substream->runtime->hw = ss->hw;
>> + substream->private_data = ss;
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * virtsnd_pcm_close() - Close the PCM substream.
>> + * @substream: Kernel ALSA substream.
>> + *
>> + * Context: Any context.
>> + * Return: 0.
>> + */
>> +static int virtsnd_pcm_close(struct snd_pcm_substream *substream)
>> +{
>> + return 0;
>> +}
>> +
>> +/**
>> + * virtsnd_pcm_hw_params() - Set the parameters of the PCM substream.
>> + * @substream: Kernel ALSA substream.
>> + * @hw_params: Hardware parameters (can be NULL).
>> + *
>> + * The function can be called both from the upper level (in this
case,
>> + * @hw_params is not NULL) or from the driver itself (in this case,
>> @hw_params
>> + * is NULL, and the parameter values are taken from the runtime
>> structure).
>> + *
>> + * In all cases, the function:
>> + * 1. checks the state of the virtqueue and, if necessary, tries to
>> fix it,
>> + * 2. sets the parameters on the device side,
>> + * 3. allocates a hardware buffer and I/O messages.
>> + *
>> + * Context: Any context that permits to sleep.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_pcm_hw_params(struct snd_pcm_substream *substream,
>> + struct snd_pcm_hw_params *hw_params)
>> +{
>> + struct snd_pcm_runtime *runtime = substream->runtime;
>> + struct virtio_pcm_substream *ss >>
snd_pcm_substream_chip(substream);
>> + struct virtio_device *vdev = ss->snd->vdev;
>> + struct virtio_snd_msg *msg;
>> + struct virtio_snd_pcm_set_params *request;
>> + snd_pcm_format_t format;
>> + unsigned int channels;
>> + unsigned int rate;
>> + unsigned int buffer_bytes;
>> + unsigned int period_bytes;
>> + unsigned int periods;
>> + unsigned int i;
>> + int vformat = -1;
>> + int vrate = -1;
>> + int rc;
>> +
>> + /*
>> + * If we got here after ops->trigger() was called, the queue
may
>> + * still contain messages. In this case, we need to release the
>> + * substream first.
>> + */
>> + if (atomic_read(&ss->msg_count)) {
>> + rc = virtsnd_pcm_release(ss);
>> + if (rc) {
>> + dev_err(&vdev->dev,
>> + "SID %u: invalid I/O queue
state\n",
>> + ss->sid);
>> + return rc;
>> + }
>> + }
>> +
>> + /* Set hardware parameters in device */
>> + if (hw_params) {
>> + format = params_format(hw_params);
>> + channels = params_channels(hw_params);
>> + rate = params_rate(hw_params);
>> + buffer_bytes = params_buffer_bytes(hw_params);
>> + period_bytes = params_period_bytes(hw_params);
>> + periods = params_periods(hw_params);
>> + } else {
>> + format = runtime->format;
>> + channels = runtime->channels;
>> + rate = runtime->rate;
>> + buffer_bytes = frames_to_bytes(runtime,
>> runtime->buffer_size);
>> + period_bytes = frames_to_bytes(runtime,
>> runtime->period_size);
>> + periods = runtime->periods;
>> + }
>> +
>> + for (i = 0; i < ARRAY_SIZE(g_a2v_format_map); ++i)
>> + if (g_a2v_format_map[i].alsa_bit == format) {
>> + vformat = g_a2v_format_map[i].vio_bit;
>> +
>> + break;
>> + }
>> +
>> + for (i = 0; i < ARRAY_SIZE(g_a2v_rate_map); ++i)
>> + if (g_a2v_rate_map[i].rate == rate) {
>> + vrate = g_a2v_rate_map[i].vio_bit;
>> +
>> + break;
>> + }
>> +
>> + if (vformat == -1 || vrate == -1)
>> + return -EINVAL;
>> +
>> + msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_SET_PARAMS,
>> + GFP_KERNEL);
>> + if (IS_ERR(msg))
>> + return PTR_ERR(msg);
>> +
>> + request = sg_virt(&msg->sg_request);
>> +
>> + request->buffer_bytes = cpu_to_virtio32(vdev, buffer_bytes);
>> + request->period_bytes = cpu_to_virtio32(vdev, period_bytes);
>> + request->channels = channels;
>> + request->format = vformat;
>> + request->rate = vrate;
>
> I presume the latter three fields don't have to be
endienness-converted,
> perhaps they're 8-bit wide only.
Yes, these three values are u8.
>> +
>> + if (ss->features & (1U <<
VIRTIO_SND_PCM_F_MSG_POLLING))
>> + request->features | >> +
cpu_to_virtio32(vdev,
>> + 1U <<
>> VIRTIO_SND_PCM_F_MSG_POLLING);
>> +
>> + if (ss->features & (1U <<
VIRTIO_SND_PCM_F_EVT_XRUNS))
>> + request->features | >> +
cpu_to_virtio32(vdev,
>> + 1U <<
VIRTIO_SND_PCM_F_EVT_XRUNS);
>> +
>> + rc = virtsnd_ctl_msg_send_sync(ss->snd, msg);
>
> Wouldn't it be better to only try to send the message after below
> allocations completed successfully?
I thought the reverse logic was better. This message asks the device to
set a specific set of parameters. And if the device returned an error
for some reason, then there is no point in allocating memory.
>> + if (rc)
>> + return rc;
>> +
>> + /* If the buffer was already allocated earlier, do nothing. */
>> + if (runtime->dma_area)
>> + return 0;
>> +
>> + /* Allocate hardware buffer */
>> + rc = snd_pcm_lib_malloc_pages(substream, buffer_bytes);
>> + if (rc < 0)
>> + return rc;
>> +
>> + /* Allocate and initialize I/O messages */
>> + rc = virtsnd_pcm_msg_alloc(ss, periods, runtime->dma_area,
>> + period_bytes);
>> + if (rc)
>> + snd_pcm_lib_free_pages(substream);
>> +
>> + return rc;
>> +}
>> +
>> +/**
>> + * virtsnd_pcm_hw_free() - Reset the parameters of the PCM substream.
>> + * @substream: Kernel ALSA substream.
>> + *
>> + * The function does the following:
>> + * 1. tries to release the PCM substream on the device side,
>> + * 2. frees the hardware buffer.
>> + *
>> + * Context: Any context that permits to sleep.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_pcm_hw_free(struct snd_pcm_substream *substream)
>> +{
>> + struct virtio_pcm_substream *ss >>
snd_pcm_substream_chip(substream);
>> + int rc;
>> +
>> + rc = virtsnd_pcm_release(ss);
>> +
>> + /*
>> + * Even if we failed to send the RELEASE message or wait for the
>> queue
>> + * flush to complete, we can safely delete the buffer. Because
>> after
>> + * receiving the STOP command, the device must stop all I/O
message
>> + * processing. If there are still pending messages in the queue,
>> the
>> + * next ops->hw_params() call should deal with this.
>> + */
>> + snd_pcm_lib_free_pages(substream);
>> +
>> + return rc;
>> +}
>> +
>> +/**
>> + * virtsnd_pcm_hw_params() - Prepare the PCM substream.
>
> copy-paste: this is virtsnd_pcm_prepare()
Oops... :)
>> + * @substream: Kernel ALSA substream.
>> + *
>> + * The function can be called both from the upper level or from the
>> driver
>> + * itself.
>> + *
>> + * In all cases, the function:
>> + * 1. checks the state of the virtqueue and, if necessary, tries to
>> fix it,
>> + * 2. prepares the substream on the device side.
>> + *
>> + * Context: Any context that permits to sleep. May take and release
>> the tx/rx
>> + * queue spinlock.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream)
>> +{
>> + struct virtio_pcm_substream *ss >>
snd_pcm_substream_chip(substream);
>> + struct virtio_snd_queue *queue = virtsnd_pcm_queue(ss);
>> + struct virtio_snd_msg *msg;
>> + unsigned long flags;
>> + int rc;
>> +
>> + /*
>> + * If we got here after ops->trigger() was called, the queue
may
>> + * still contain messages. In this case, we need to reset the
>> + * substream first.
>> + */
>> + if (atomic_read(&ss->msg_count)) {
>> + rc = virtsnd_pcm_hw_params(substream, NULL);
>> + if (rc)
>> + return rc;
>> + }
>> +
>> + spin_lock_irqsave(&queue->lock, flags);
>> + ss->msg_last_enqueued = -1;
>> + spin_unlock_irqrestore(&queue->lock, flags);
>> +
>> + /*
>> + * Since I/O messages are asynchronous, they can be completed
>> + * when the runtime structure no longer exists. Since each
>> + * completion implies incrementing the hw_ptr, we cache all the
>> + * current values needed to compute the new hw_ptr value.
>> + */
>> + ss->frame_bytes = substream->runtime->frame_bits
>> 3;
>> + ss->period_size = substream->runtime->period_size;
>> + ss->buffer_size = substream->runtime->buffer_size;
>> +
>> + atomic_set(&ss->hw_ptr, 0);
>> + atomic_set(&ss->xfer_xrun, 0);
>> + atomic_set(&ss->msg_count, 0);
>> +
>> + msg = virtsnd_pcm_ctl_msg_alloc(ss, VIRTIO_SND_R_PCM_PREPARE,
>> + GFP_KERNEL);
>> + if (IS_ERR(msg))
>> + return PTR_ERR(msg);
>> +
>> + return virtsnd_ctl_msg_send_sync(ss->snd, msg);
>> +}
>> +
>> +/**
>> + * virtsnd_pcm_trigger() - Process command for the PCM substream.
>> + * @substream: Kernel ALSA substream.
>> + * @command: Substream command (SNDRV_PCM_TRIGGER_XXX).
>> + *
>> + * Depending on the command, the function does the following:
>> + * 1. enables/disables data transmission,
>> + * 2. starts/stops the substream on the device side.
>> + *
>> + * Context: Atomic context. May take and release the tx/rx queue
>> spinlock.
>
> Really? Cannot .trigger() sleep? E.g. I see mdelay(25) in
> snd_es18xx_playback1_trigger()
Actually, you made a good point here. I didn't know, that it is possible
to disable atomic mode for that callback. But, apparently, it is possible.
And virtio pcm definetly is nonatomic. I need to redo this code, thanks!
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream,
>> int command)
>> +{
>> + struct virtio_pcm_substream *ss >>
snd_pcm_substream_chip(substream);
>> + struct virtio_snd *snd = ss->snd;
>> + struct virtio_snd_queue *queue = virtsnd_pcm_queue(ss);
>> + struct virtio_snd_msg *msg;
>> +
>> + switch (command) {
>> + case SNDRV_PCM_TRIGGER_START:
>> + case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: {
>> + int rc;
>> +
>> + spin_lock(&queue->lock);
>> + rc = virtsnd_pcm_msg_send(ss);
>> + spin_unlock(&queue->lock);
>
> Maybe it would be good to explain why locking is required here and
isn't
> required in most other locations, where messages are sent?
There are two kinds of messages here: control messages and I/O. Functions
for sending control message acquire and release the control virtqueue
spinlock on their own. But we cannot do the same for I/O messages, since
virtsnd_pcm_msg_send is also called from the interrupt handler, which is
already grabbing the lock for the I/O virtqueue.
> Thanks
> Guennadi
>
>> + if (rc)
>> + return rc;
>> +
>> + atomic_set(&ss->xfer_enabled, 1);
>> +
>> + msg = virtsnd_pcm_ctl_msg_alloc(ss,
VIRTIO_SND_R_PCM_START,
>> + GFP_ATOMIC);
>> + if (IS_ERR(msg))
>> + return PTR_ERR(msg);
>> +
>> + return virtsnd_ctl_msg_send(snd, msg);
>> + }
>> + case SNDRV_PCM_TRIGGER_STOP:
>> + case SNDRV_PCM_TRIGGER_PAUSE_PUSH: {
>> + atomic_set(&ss->xfer_enabled, 0);
>> +
>> + msg = virtsnd_pcm_ctl_msg_alloc(ss,
VIRTIO_SND_R_PCM_STOP,
>> + GFP_ATOMIC);
>> + if (IS_ERR(msg))
>> + return PTR_ERR(msg);
>> +
>> + return virtsnd_ctl_msg_send(snd, msg);
>> + }
>> + default: {
>> + return -EINVAL;
>> + }
>> + }
>> +}
--
Anton Yakovlev
Senior Software Engineer
OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin
www.opensynergy.com