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fe981e6756
This commit uses the ack() callback to determine when a buffer has been updated, then exposes it to guest. The current mechanism splits a dma buffer into descriptors that are exposed to the device. This dma buffer is shared with the user application. When the device consumes a buffer, the driver moves the request from the used ring to available ring. The driver exposes the buffer to the device without knowing if the content has been updated from the user. The section 2.8.21.1 of the virtio spec states that: "The device MAY access the descriptor chains the driver created and the memory they refer to immediately". If the device picks up buffers from the available ring just after it is notified, it happens that the content may be old. When the ack() callback is invoked, the driver exposes only the buffers that have already been updated, i.e., enqueued in the available ring. Thus, the device always picks up a buffer that is updated. For capturing, the driver starts by exposing all the available buffers to device. After device updates the content of a buffer, it enqueues it in the used ring. It is only after the ack() for capturing is issued that the driver re-enqueues the buffer in the available ring. Co-developed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> Link: https://lore.kernel.org/r/ZTjkn1YAFz67yfqx@fedora Signed-off-by: Takashi Iwai <tiwai@suse.de>
127 lines
3.9 KiB
C
127 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* virtio-snd: Virtio sound device
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* Copyright (C) 2021 OpenSynergy GmbH
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*/
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#ifndef VIRTIO_SND_PCM_H
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#define VIRTIO_SND_PCM_H
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#include <linux/atomic.h>
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#include <linux/virtio_config.h>
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#include <sound/pcm.h>
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#include <sound/pcm-indirect.h>
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struct virtio_pcm;
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struct virtio_pcm_msg;
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/**
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* struct virtio_pcm_substream - VirtIO PCM substream.
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* @snd: VirtIO sound device.
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* @nid: Function group node identifier.
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* @sid: Stream identifier.
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* @direction: Stream data flow direction (SNDRV_PCM_STREAM_XXX).
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* @features: Stream VirtIO feature bit map (1 << VIRTIO_SND_PCM_F_XXX).
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* @substream: Kernel ALSA substream.
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* @pcm_indirect: Kernel indirect pcm structure.
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* @hw: Kernel ALSA substream hardware descriptor.
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* @elapsed_period: Kernel work to handle the elapsed period state.
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* @lock: Spinlock that protects fields shared by interrupt handlers and
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* substream operators.
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* @buffer_bytes: Current buffer size in bytes.
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* @hw_ptr: Substream hardware pointer value in bytes [0 ... buffer_bytes).
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* @xfer_enabled: Data transfer state (0 - off, 1 - on).
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* @xfer_xrun: Data underflow/overflow state (0 - no xrun, 1 - xrun).
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* @stopped: True if the substream is stopped and must be released on the device
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* side.
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* @suspended: True if the substream is suspended and must be reconfigured on
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* the device side at resume.
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* @msgs: Allocated I/O messages.
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* @nmsgs: Number of allocated I/O messages.
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* @msg_last_enqueued: Index of the last I/O message added to the virtqueue.
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* @msg_count: Number of pending I/O messages in the virtqueue.
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* @msg_empty: Notify when msg_count is zero.
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*/
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struct virtio_pcm_substream {
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struct virtio_snd *snd;
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u32 nid;
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u32 sid;
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u32 direction;
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u32 features;
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struct snd_pcm_substream *substream;
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struct snd_pcm_indirect pcm_indirect;
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struct snd_pcm_hardware hw;
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struct work_struct elapsed_period;
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spinlock_t lock;
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size_t buffer_bytes;
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size_t hw_ptr;
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bool xfer_enabled;
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bool xfer_xrun;
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bool stopped;
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bool suspended;
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struct virtio_pcm_msg **msgs;
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unsigned int nmsgs;
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unsigned int msg_count;
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wait_queue_head_t msg_empty;
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};
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/**
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* struct virtio_pcm_stream - VirtIO PCM stream.
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* @substreams: VirtIO substreams belonging to the stream.
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* @nsubstreams: Number of substreams.
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* @chmaps: Kernel channel maps belonging to the stream.
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* @nchmaps: Number of channel maps.
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*/
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struct virtio_pcm_stream {
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struct virtio_pcm_substream **substreams;
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u32 nsubstreams;
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struct snd_pcm_chmap_elem *chmaps;
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u32 nchmaps;
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};
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/**
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* struct virtio_pcm - VirtIO PCM device.
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* @list: VirtIO PCM list entry.
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* @nid: Function group node identifier.
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* @pcm: Kernel PCM device.
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* @streams: VirtIO PCM streams (playback and capture).
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*/
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struct virtio_pcm {
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struct list_head list;
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u32 nid;
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struct snd_pcm *pcm;
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struct virtio_pcm_stream streams[SNDRV_PCM_STREAM_LAST + 1];
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};
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extern const struct snd_pcm_ops virtsnd_pcm_ops[];
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int virtsnd_pcm_validate(struct virtio_device *vdev);
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int virtsnd_pcm_parse_cfg(struct virtio_snd *snd);
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int virtsnd_pcm_build_devs(struct virtio_snd *snd);
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void virtsnd_pcm_event(struct virtio_snd *snd, struct virtio_snd_event *event);
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void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue);
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void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue);
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struct virtio_pcm *virtsnd_pcm_find(struct virtio_snd *snd, u32 nid);
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struct virtio_pcm *virtsnd_pcm_find_or_create(struct virtio_snd *snd, u32 nid);
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struct virtio_snd_msg *
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virtsnd_pcm_ctl_msg_alloc(struct virtio_pcm_substream *vss,
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unsigned int command, gfp_t gfp);
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int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss,
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unsigned int periods, unsigned int period_bytes);
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void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss);
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int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss, unsigned long offset,
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unsigned long bytes);
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unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss);
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#endif /* VIRTIO_SND_PCM_H */
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