--- /dev/null
+From d4c8a3a4b9de5a25b6963f3ae1b8a5cb32081de5 Mon Sep 17 00:00:00 2001
+From: Anton Yakovlev <anton.yakovlev@opensynergy.com>
+Date: Tue, 2 Mar 2021 17:47:03 +0100
+Subject: [PATCH] ALSA: virtio: handling control messages
+
+The control queue can be used by different parts of the driver to send
+commands to the device. Control messages can be either synchronous or
+asynchronous. The lifetime of a message is controlled by a reference
+count.
+
+Introduce a module parameter to set the message completion timeout:
+ msg_timeout_ms [=1000]
+
+Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
+Link: https://lore.kernel.org/r/20210302164709.3142702-4-anton.yakovlev@opensynergy.com
+Signed-off-by: Takashi Iwai <tiwai@suse.de>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ sound/virtio/Makefile | 3 +-
+ sound/virtio/virtio_card.c | 13 ++
+ sound/virtio/virtio_card.h | 7 +
+ sound/virtio/virtio_ctl_msg.c | 310 ++++++++++++++++++++++++++++++++++
+ sound/virtio/virtio_ctl_msg.h | 78 +++++++++
+ 5 files changed, 410 insertions(+), 1 deletion(-)
+ create mode 100644 sound/virtio/virtio_ctl_msg.c
+ create mode 100644 sound/virtio/virtio_ctl_msg.h
+
+diff --git a/sound/virtio/Makefile b/sound/virtio/Makefile
+index 8c87ebb9982b..dc551e637441 100644
+--- a/sound/virtio/Makefile
++++ b/sound/virtio/Makefile
+@@ -3,5 +3,6 @@
+ obj-$(CONFIG_SND_VIRTIO) += virtio_snd.o
+
+ virtio_snd-objs := \
+- virtio_card.o
++ virtio_card.o \
++ virtio_ctl_msg.o
+
+diff --git a/sound/virtio/virtio_card.c b/sound/virtio/virtio_card.c
+index 5a37056858e9..b757b2444078 100644
+--- a/sound/virtio/virtio_card.c
++++ b/sound/virtio/virtio_card.c
+@@ -11,6 +11,10 @@
+
+ #include "virtio_card.h"
+
++u32 virtsnd_msg_timeout_ms = MSEC_PER_SEC;
++module_param_named(msg_timeout_ms, virtsnd_msg_timeout_ms, uint, 0644);
++MODULE_PARM_DESC(msg_timeout_ms, "Message completion timeout in milliseconds");
++
+ static void virtsnd_remove(struct virtio_device *vdev);
+
+ /**
+@@ -96,9 +100,11 @@ static int virtsnd_find_vqs(struct virtio_snd *snd)
+ {
+ struct virtio_device *vdev = snd->vdev;
+ static vq_callback_t *callbacks[VIRTIO_SND_VQ_MAX] = {
++ [VIRTIO_SND_VQ_CONTROL] = virtsnd_ctl_notify_cb,
+ [VIRTIO_SND_VQ_EVENT] = virtsnd_event_notify_cb
+ };
+ static const char *names[VIRTIO_SND_VQ_MAX] = {
++ [VIRTIO_SND_VQ_CONTROL] = "virtsnd-ctl",
+ [VIRTIO_SND_VQ_EVENT] = "virtsnd-event"
+ };
+ struct virtqueue *vqs[VIRTIO_SND_VQ_MAX] = { 0 };
+@@ -226,6 +232,11 @@ static int virtsnd_validate(struct virtio_device *vdev)
+ return -EINVAL;
+ }
+
++ if (!virtsnd_msg_timeout_ms) {
++ dev_err(&vdev->dev, "msg_timeout_ms value cannot be zero\n");
++ return -EINVAL;
++ }
++
+ return 0;
+ }
+
+@@ -247,6 +258,7 @@ static int virtsnd_probe(struct virtio_device *vdev)
+ return -ENOMEM;
+
+ snd->vdev = vdev;
++ INIT_LIST_HEAD(&snd->ctl_msgs);
+
+ vdev->priv = snd;
+
+@@ -283,6 +295,7 @@ static void virtsnd_remove(struct virtio_device *vdev)
+ struct virtio_snd *snd = vdev->priv;
+
+ virtsnd_disable_event_vq(snd);
++ virtsnd_ctl_msg_cancel_all(snd);
+
+ if (snd->card)
+ snd_card_free(snd->card);
+diff --git a/sound/virtio/virtio_card.h b/sound/virtio/virtio_card.h
+index b903b1b12e90..1e76eeff160f 100644
+--- a/sound/virtio/virtio_card.h
++++ b/sound/virtio/virtio_card.h
+@@ -11,6 +11,8 @@
+ #include <sound/core.h>
+ #include <uapi/linux/virtio_snd.h>
+
++#include "virtio_ctl_msg.h"
++
+ #define VIRTIO_SND_CARD_DRIVER "virtio-snd"
+ #define VIRTIO_SND_CARD_NAME "VirtIO SoundCard"
+
+@@ -29,15 +31,20 @@ struct virtio_snd_queue {
+ * @vdev: Underlying virtio device.
+ * @queues: Virtqueue wrappers.
+ * @card: ALSA sound card.
++ * @ctl_msgs: Pending control request list.
+ * @event_msgs: Device events.
+ */
+ struct virtio_snd {
+ struct virtio_device *vdev;
+ struct virtio_snd_queue queues[VIRTIO_SND_VQ_MAX];
+ struct snd_card *card;
++ struct list_head ctl_msgs;
+ struct virtio_snd_event *event_msgs;
+ };
+
++/* Message completion timeout in milliseconds (module parameter). */
++extern u32 virtsnd_msg_timeout_ms;
++
+ static inline struct virtio_snd_queue *
+ virtsnd_control_queue(struct virtio_snd *snd)
+ {
+diff --git a/sound/virtio/virtio_ctl_msg.c b/sound/virtio/virtio_ctl_msg.c
+new file mode 100644
+index 000000000000..26ff7e7cc041
+--- /dev/null
++++ b/sound/virtio/virtio_ctl_msg.c
+@@ -0,0 +1,310 @@
++// SPDX-License-Identifier: GPL-2.0+
++/*
++ * virtio-snd: Virtio sound device
++ * Copyright (C) 2021 OpenSynergy GmbH
++ */
++#include <linux/moduleparam.h>
++#include <linux/virtio_config.h>
++
++#include "virtio_card.h"
++
++/**
++ * struct virtio_snd_msg - Control message.
++ * @sg_request: Scattergather list containing a device request (header).
++ * @sg_response: Scattergather list containing a device response (status).
++ * @list: Pending message list entry.
++ * @notify: Request completed notification.
++ * @ref_count: Reference count used to manage a message lifetime.
++ */
++struct virtio_snd_msg {
++ struct scatterlist sg_request;
++ struct scatterlist sg_response;
++ struct list_head list;
++ struct completion notify;
++ refcount_t ref_count;
++};
++
++/**
++ * virtsnd_ctl_msg_ref() - Increment reference counter for the message.
++ * @msg: Control message.
++ *
++ * Context: Any context.
++ */
++void virtsnd_ctl_msg_ref(struct virtio_snd_msg *msg)
++{
++ refcount_inc(&msg->ref_count);
++}
++
++/**
++ * virtsnd_ctl_msg_unref() - Decrement reference counter for the message.
++ * @msg: Control message.
++ *
++ * The message will be freed when the ref_count value is 0.
++ *
++ * Context: Any context.
++ */
++void virtsnd_ctl_msg_unref(struct virtio_snd_msg *msg)
++{
++ if (refcount_dec_and_test(&msg->ref_count))
++ kfree(msg);
++}
++
++/**
++ * virtsnd_ctl_msg_request() - Get a pointer to the request header.
++ * @msg: Control message.
++ *
++ * Context: Any context.
++ */
++void *virtsnd_ctl_msg_request(struct virtio_snd_msg *msg)
++{
++ return sg_virt(&msg->sg_request);
++}
++
++/**
++ * virtsnd_ctl_msg_request() - Get a pointer to the response header.
++ * @msg: Control message.
++ *
++ * Context: Any context.
++ */
++void *virtsnd_ctl_msg_response(struct virtio_snd_msg *msg)
++{
++ return sg_virt(&msg->sg_response);
++}
++
++/**
++ * virtsnd_ctl_msg_alloc() - Allocate and initialize a control message.
++ * @request_size: Size of request header.
++ * @response_size: Size of response header.
++ * @gfp: Kernel flags for memory allocation.
++ *
++ * The message will be automatically freed when the ref_count value is 0.
++ *
++ * Context: Any context. May sleep if @gfp flags permit.
++ * Return: Allocated message on success, NULL on failure.
++ */
++struct virtio_snd_msg *virtsnd_ctl_msg_alloc(size_t request_size,
++ size_t response_size, gfp_t gfp)
++{
++ struct virtio_snd_msg *msg;
++
++ if (!request_size || !response_size)
++ return NULL;
++
++ msg = kzalloc(sizeof(*msg) + request_size + response_size, gfp);
++ if (!msg)
++ return NULL;
++
++ sg_init_one(&msg->sg_request, (u8 *)msg + sizeof(*msg), request_size);
++ sg_init_one(&msg->sg_response, (u8 *)msg + sizeof(*msg) + request_size,
++ response_size);
++
++ INIT_LIST_HEAD(&msg->list);
++ init_completion(&msg->notify);
++ /* This reference is dropped in virtsnd_ctl_msg_complete(). */
++ refcount_set(&msg->ref_count, 1);
++
++ return msg;
++}
++
++/**
++ * virtsnd_ctl_msg_send() - Send a control message.
++ * @snd: VirtIO sound device.
++ * @msg: Control message.
++ * @out_sgs: Additional sg-list to attach to the request header (may be NULL).
++ * @in_sgs: Additional sg-list to attach to the response header (may be NULL).
++ * @nowait: Flag indicating whether to wait for completion.
++ *
++ * Context: Any context. Takes and releases the control queue spinlock.
++ * May sleep if @nowait is false.
++ * Return: 0 on success, -errno on failure.
++ */
++int virtsnd_ctl_msg_send(struct virtio_snd *snd, struct virtio_snd_msg *msg,
++ struct scatterlist *out_sgs,
++ struct scatterlist *in_sgs, bool nowait)
++{
++ struct virtio_device *vdev = snd->vdev;
++ struct virtio_snd_queue *queue = virtsnd_control_queue(snd);
++ unsigned int js = msecs_to_jiffies(virtsnd_msg_timeout_ms);
++ struct virtio_snd_hdr *request = virtsnd_ctl_msg_request(msg);
++ struct virtio_snd_hdr *response = virtsnd_ctl_msg_response(msg);
++ unsigned int nouts = 0;
++ unsigned int nins = 0;
++ struct scatterlist *psgs[4];
++ bool notify = false;
++ unsigned long flags;
++ int rc;
++
++ virtsnd_ctl_msg_ref(msg);
++
++ /* Set the default status in case the message was canceled. */
++ response->code = cpu_to_le32(VIRTIO_SND_S_IO_ERR);
++
++ psgs[nouts++] = &msg->sg_request;
++ if (out_sgs)
++ psgs[nouts++] = out_sgs;
++
++ psgs[nouts + nins++] = &msg->sg_response;
++ if (in_sgs)
++ psgs[nouts + nins++] = in_sgs;
++
++ spin_lock_irqsave(&queue->lock, flags);
++ rc = virtqueue_add_sgs(queue->vqueue, psgs, nouts, nins, msg,
++ GFP_ATOMIC);
++ if (!rc) {
++ notify = virtqueue_kick_prepare(queue->vqueue);
++
++ list_add_tail(&msg->list, &snd->ctl_msgs);
++ }
++ spin_unlock_irqrestore(&queue->lock, flags);
++
++ if (rc) {
++ dev_err(&vdev->dev, "failed to send control message (0x%08x)\n",
++ le32_to_cpu(request->code));
++
++ /*
++ * Since in this case virtsnd_ctl_msg_complete() will not be
++ * called, it is necessary to decrement the reference count.
++ */
++ virtsnd_ctl_msg_unref(msg);
++
++ goto on_exit;
++ }
++
++ if (notify)
++ virtqueue_notify(queue->vqueue);
++
++ if (nowait)
++ goto on_exit;
++
++ rc = wait_for_completion_interruptible_timeout(&msg->notify, js);
++ if (rc <= 0) {
++ if (!rc) {
++ dev_err(&vdev->dev,
++ "control message (0x%08x) timeout\n",
++ le32_to_cpu(request->code));
++ rc = -ETIMEDOUT;
++ }
++
++ goto on_exit;
++ }
++
++ switch (le32_to_cpu(response->code)) {
++ case VIRTIO_SND_S_OK:
++ rc = 0;
++ break;
++ case VIRTIO_SND_S_NOT_SUPP:
++ rc = -EOPNOTSUPP;
++ break;
++ case VIRTIO_SND_S_IO_ERR:
++ rc = -EIO;
++ break;
++ default:
++ rc = -EINVAL;
++ break;
++ }
++
++on_exit:
++ virtsnd_ctl_msg_unref(msg);
++
++ return rc;
++}
++
++/**
++ * virtsnd_ctl_msg_complete() - Complete a control message.
++ * @msg: Control message.
++ *
++ * Context: Any context. Expects the control queue spinlock to be held by
++ * caller.
++ */
++void virtsnd_ctl_msg_complete(struct virtio_snd_msg *msg)
++{
++ list_del(&msg->list);
++ complete(&msg->notify);
++
++ virtsnd_ctl_msg_unref(msg);
++}
++
++/**
++ * virtsnd_ctl_msg_cancel_all() - Cancel all pending control messages.
++ * @snd: VirtIO sound device.
++ *
++ * Context: Any context.
++ */
++void virtsnd_ctl_msg_cancel_all(struct virtio_snd *snd)
++{
++ struct virtio_snd_queue *queue = virtsnd_control_queue(snd);
++ unsigned long flags;
++
++ spin_lock_irqsave(&queue->lock, flags);
++ while (!list_empty(&snd->ctl_msgs)) {
++ struct virtio_snd_msg *msg =
++ list_first_entry(&snd->ctl_msgs, struct virtio_snd_msg,
++ list);
++
++ virtsnd_ctl_msg_complete(msg);
++ }
++ spin_unlock_irqrestore(&queue->lock, flags);
++}
++
++/**
++ * virtsnd_ctl_query_info() - Query the item configuration from the device.
++ * @snd: VirtIO sound device.
++ * @command: Control request code (VIRTIO_SND_R_XXX_INFO).
++ * @start_id: Item start identifier.
++ * @count: Item count to query.
++ * @size: Item information size in bytes.
++ * @info: Buffer for storing item information.
++ *
++ * Context: Any context that permits to sleep.
++ * Return: 0 on success, -errno on failure.
++ */
++int virtsnd_ctl_query_info(struct virtio_snd *snd, int command, int start_id,
++ int count, size_t size, void *info)
++{
++ struct virtio_snd_msg *msg;
++ struct virtio_snd_query_info *query;
++ struct scatterlist sg;
++
++ msg = virtsnd_ctl_msg_alloc(sizeof(*query),
++ sizeof(struct virtio_snd_hdr), GFP_KERNEL);
++ if (!msg)
++ return -ENOMEM;
++
++ query = virtsnd_ctl_msg_request(msg);
++ query->hdr.code = cpu_to_le32(command);
++ query->start_id = cpu_to_le32(start_id);
++ query->count = cpu_to_le32(count);
++ query->size = cpu_to_le32(size);
++
++ sg_init_one(&sg, info, count * size);
++
++ return virtsnd_ctl_msg_send(snd, msg, NULL, &sg, false);
++}
++
++/**
++ * virtsnd_ctl_notify_cb() - Process all completed control messages.
++ * @vqueue: Underlying control virtqueue.
++ *
++ * This callback function is called upon a vring interrupt request from the
++ * device.
++ *
++ * Context: Interrupt context. Takes and releases the control queue spinlock.
++ */
++void virtsnd_ctl_notify_cb(struct virtqueue *vqueue)
++{
++ struct virtio_snd *snd = vqueue->vdev->priv;
++ struct virtio_snd_queue *queue = virtsnd_control_queue(snd);
++ struct virtio_snd_msg *msg;
++ u32 length;
++ unsigned long flags;
++
++ spin_lock_irqsave(&queue->lock, flags);
++ do {
++ virtqueue_disable_cb(vqueue);
++ while ((msg = virtqueue_get_buf(vqueue, &length)))
++ virtsnd_ctl_msg_complete(msg);
++ if (unlikely(virtqueue_is_broken(vqueue)))
++ break;
++ } while (!virtqueue_enable_cb(vqueue));
++ spin_unlock_irqrestore(&queue->lock, flags);
++}
+diff --git a/sound/virtio/virtio_ctl_msg.h b/sound/virtio/virtio_ctl_msg.h
+new file mode 100644
+index 000000000000..7f4db044f28e
+--- /dev/null
++++ b/sound/virtio/virtio_ctl_msg.h
+@@ -0,0 +1,78 @@
++/* SPDX-License-Identifier: GPL-2.0+ */
++/*
++ * virtio-snd: Virtio sound device
++ * Copyright (C) 2021 OpenSynergy GmbH
++ */
++#ifndef VIRTIO_SND_MSG_H
++#define VIRTIO_SND_MSG_H
++
++#include <linux/atomic.h>
++#include <linux/virtio.h>
++
++struct virtio_snd;
++struct virtio_snd_msg;
++
++void virtsnd_ctl_msg_ref(struct virtio_snd_msg *msg);
++
++void virtsnd_ctl_msg_unref(struct virtio_snd_msg *msg);
++
++void *virtsnd_ctl_msg_request(struct virtio_snd_msg *msg);
++
++void *virtsnd_ctl_msg_response(struct virtio_snd_msg *msg);
++
++struct virtio_snd_msg *virtsnd_ctl_msg_alloc(size_t request_size,
++ size_t response_size, gfp_t gfp);
++
++int virtsnd_ctl_msg_send(struct virtio_snd *snd, struct virtio_snd_msg *msg,
++ struct scatterlist *out_sgs,
++ struct scatterlist *in_sgs, bool nowait);
++
++/**
++ * virtsnd_ctl_msg_send_sync() - Simplified sending of synchronous message.
++ * @snd: VirtIO sound device.
++ * @msg: Control message.
++ *
++ * After returning from this function, the message will be deleted. If message
++ * content is still needed, the caller must additionally to
++ * virtsnd_ctl_msg_ref/unref() it.
++ *
++ * The msg_timeout_ms module parameter defines the message completion timeout.
++ * If the message is not completed within this time, the function will return an
++ * error.
++ *
++ * Context: Any context that permits to sleep.
++ * Return: 0 on success, -errno on failure.
++ *
++ * The return value is a message status code (VIRTIO_SND_S_XXX) converted to an
++ * appropriate -errno value.
++ */
++static inline int virtsnd_ctl_msg_send_sync(struct virtio_snd *snd,
++ struct virtio_snd_msg *msg)
++{
++ return virtsnd_ctl_msg_send(snd, msg, NULL, NULL, false);
++}
++
++/**
++ * virtsnd_ctl_msg_send_async() - Simplified sending of asynchronous message.
++ * @snd: VirtIO sound device.
++ * @msg: Control message.
++ *
++ * Context: Any context.
++ * Return: 0 on success, -errno on failure.
++ */
++static inline int virtsnd_ctl_msg_send_async(struct virtio_snd *snd,
++ struct virtio_snd_msg *msg)
++{
++ return virtsnd_ctl_msg_send(snd, msg, NULL, NULL, true);
++}
++
++void virtsnd_ctl_msg_cancel_all(struct virtio_snd *snd);
++
++void virtsnd_ctl_msg_complete(struct virtio_snd_msg *msg);
++
++int virtsnd_ctl_query_info(struct virtio_snd *snd, int command, int start_id,
++ int count, size_t size, void *info);
++
++void virtsnd_ctl_notify_cb(struct virtqueue *vqueue);
++
++#endif /* VIRTIO_SND_MSG_H */
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