sound/xen/xen_snd_front_evtchnl.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0 OR MIT

 /*
  * Xen para-virtual sound device
  *
  * Copyright (C) 2016-2018 EPAM Systems Inc.
  *
  * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
  */

 #include <xen/events.h>
 #include <xen/grant_table.h>
 #include <xen/xen.h>
 #include <xen/xenbus.h>

 #include "xen_snd_front.h"
 #include "xen_snd_front_alsa.h"
 #include "xen_snd_front_cfg.h"
 #include "xen_snd_front_evtchnl.h"

 static irqreturn_t evtchnl_interrupt_req(int irq, void *dev_id)
 {
 	struct xen_snd_front_evtchnl *channel = dev_id;
 	struct xen_snd_front_info *front_info = channel->front_info;
 	struct xensnd_resp *resp;
 	RING_IDX i, rp;

 	if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED))
 		return IRQ_HANDLED;

 	mutex_lock(&channel->ring_io_lock);

 again:
 	rp = channel->u.req.ring.sring->rsp_prod;
 	/* Ensure we see queued responses up to rp. */
 	rmb();

 	/*
 	 * Assume that the backend is trusted to always write sane values
 	 * to the ring counters, so no overflow checks on frontend side
 	 * are required.
 	 */
 	for (i = channel->u.req.ring.rsp_cons; i != rp; i++) {
 		resp = RING_GET_RESPONSE(&channel->u.req.ring, i);
 		if (resp->id != channel->evt_id)
 			continue;
 		switch (resp->operation) {
 		case XENSND_OP_OPEN:
 		case XENSND_OP_CLOSE:
 		case XENSND_OP_READ:
 		case XENSND_OP_WRITE:
 		case XENSND_OP_TRIGGER:
 			channel->u.req.resp_status = resp->status;
 			complete(&channel->u.req.completion);
 			break;
 		case XENSND_OP_HW_PARAM_QUERY:
 			channel->u.req.resp_status = resp->status;
 			channel->u.req.resp.hw_param =
 					resp->resp.hw_param;
 			complete(&channel->u.req.completion);
 			break;

 		default:
 			dev_err(&front_info->xb_dev->dev,
 				"Operation %d is not supported\n",
 				resp->operation);
 			break;
 		}
 	}

 	channel->u.req.ring.rsp_cons = i;
 	if (i != channel->u.req.ring.req_prod_pvt) {
 		int more_to_do;

 		RING_FINAL_CHECK_FOR_RESPONSES(&channel->u.req.ring,
 					       more_to_do);
 		if (more_to_do)
 			goto again;
 	} else {
 		channel->u.req.ring.sring->rsp_event = i + 1;
 	}

 	mutex_unlock(&channel->ring_io_lock);
 	return IRQ_HANDLED;
 }

 static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
 {
 	struct xen_snd_front_evtchnl *channel = dev_id;
 	struct xensnd_event_page *page = channel->u.evt.page;
 	u32 cons, prod;

 	if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED))
 		return IRQ_HANDLED;

 	mutex_lock(&channel->ring_io_lock);

 	prod = page->in_prod;
 	/* Ensure we see ring contents up to prod. */
 	virt_rmb();
 	if (prod == page->in_cons)
 		goto out;

 	/*
 	 * Assume that the backend is trusted to always write sane values
 	 * to the ring counters, so no overflow checks on frontend side
 	 * are required.
 	 */
 	for (cons = page->in_cons; cons != prod; cons++) {
 		struct xensnd_evt *event;

 		event = &XENSND_IN_RING_REF(page, cons);
 		if (unlikely(event->id != channel->evt_id++))
 			continue;

 		switch (event->type) {
 		case XENSND_EVT_CUR_POS:
 			xen_snd_front_alsa_handle_cur_pos(channel,
 							  event->op.cur_pos.position);
 			break;
 		}
 	}

 	page->in_cons = cons;
 	/* Ensure ring contents. */
 	virt_wmb();

 out:
 	mutex_unlock(&channel->ring_io_lock);
 	return IRQ_HANDLED;
 }

 void xen_snd_front_evtchnl_flush(struct xen_snd_front_evtchnl *channel)
 {
 	int notify;

 	channel->u.req.ring.req_prod_pvt++;
 	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&channel->u.req.ring, notify);
 	if (notify)
 		notify_remote_via_irq(channel->irq);
 }

 static void evtchnl_free(struct xen_snd_front_info *front_info,
 			 struct xen_snd_front_evtchnl *channel)
 {
 	void *page = NULL;

 	if (channel->type == EVTCHNL_TYPE_REQ)
 		page = channel->u.req.ring.sring;
 	else if (channel->type == EVTCHNL_TYPE_EVT)
 		page = channel->u.evt.page;

 	if (!page)
 		return;

 	channel->state = EVTCHNL_STATE_DISCONNECTED;
 	if (channel->type == EVTCHNL_TYPE_REQ) {
 		/* Release all who still waits for response if any. */
 		channel->u.req.resp_status = -EIO;
 		complete_all(&channel->u.req.completion);
 	}

 	if (channel->irq)
 		unbind_from_irqhandler(channel->irq, channel);

 	if (channel->port)
 		xenbus_free_evtchn(front_info->xb_dev, channel->port);

 	/* End access and free the page. */
 	xenbus_teardown_ring(&page, 1, &channel->gref);

 	memset(channel, 0, sizeof(*channel));
 }

 void xen_snd_front_evtchnl_free_all(struct xen_snd_front_info *front_info)
 {
 	int i;

 	if (!front_info->evt_pairs)
 		return;

 	for (i = 0; i < front_info->num_evt_pairs; i++) {
 		evtchnl_free(front_info, &front_info->evt_pairs[i].req);
 		evtchnl_free(front_info, &front_info->evt_pairs[i].evt);
 	}

 	kfree(front_info->evt_pairs);
 	front_info->evt_pairs = NULL;
 }

 static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
 			 struct xen_snd_front_evtchnl *channel,
 			 enum xen_snd_front_evtchnl_type type)
 {
 	struct xenbus_device *xb_dev = front_info->xb_dev;
 	void *page;
 	irq_handler_t handler;
 	char *handler_name = NULL;
 	int ret;

 	memset(channel, 0, sizeof(*channel));
 	channel->type = type;
 	channel->index = index;
 	channel->front_info = front_info;
 	channel->state = EVTCHNL_STATE_DISCONNECTED;
 	ret = xenbus_setup_ring(xb_dev, GFP_KERNEL, &page, 1, &channel->gref);
 	if (ret)
 		goto fail;

 	handler_name = kasprintf(GFP_KERNEL, "%s-%s", XENSND_DRIVER_NAME,
 				 type == EVTCHNL_TYPE_REQ ?
 				 XENSND_FIELD_RING_REF :
 				 XENSND_FIELD_EVT_RING_REF);
 	if (!handler_name) {
 		ret = -ENOMEM;
 		goto fail;
 	}

 	mutex_init(&channel->ring_io_lock);

 	if (type == EVTCHNL_TYPE_REQ) {
 		struct xen_sndif_sring *sring = page;

 		init_completion(&channel->u.req.completion);
 		mutex_init(&channel->u.req.req_io_lock);
 		XEN_FRONT_RING_INIT(&channel->u.req.ring, sring, XEN_PAGE_SIZE);

 		handler = evtchnl_interrupt_req;
 	} else {
 		channel->u.evt.page = page;
 		handler = evtchnl_interrupt_evt;
 	}

 	ret = xenbus_alloc_evtchn(xb_dev, &channel->port);
 	if (ret < 0)
 		goto fail;

 	ret = bind_evtchn_to_irq(channel->port);
 	if (ret < 0) {
 		dev_err(&xb_dev->dev,
 			"Failed to bind IRQ for domid %d port %d: %d\n",
 			front_info->xb_dev->otherend_id, channel->port, ret);
 		goto fail;
 	}

 	channel->irq = ret;

 	ret = request_threaded_irq(channel->irq, NULL, handler,
 				   IRQF_ONESHOT, handler_name, channel);
 	if (ret < 0) {
 		dev_err(&xb_dev->dev, "Failed to request IRQ %d: %d\n",
 			channel->irq, ret);
 		goto fail;
 	}

 	kfree(handler_name);
 	return 0;

 fail:
 	kfree(handler_name);
 	dev_err(&xb_dev->dev, "Failed to allocate ring: %d\n", ret);
 	return ret;
 }

 int xen_snd_front_evtchnl_create_all(struct xen_snd_front_info *front_info,
 				     int num_streams)
 {
 	struct xen_front_cfg_card *cfg = &front_info->cfg;
 	struct device *dev = &front_info->xb_dev->dev;
 	int d, ret = 0;

 	front_info->evt_pairs =
 			kcalloc(num_streams,
 				sizeof(struct xen_snd_front_evtchnl_pair),
 				GFP_KERNEL);
 	if (!front_info->evt_pairs)
 		return -ENOMEM;

 	/* Iterate over devices and their streams and create event channels. */
 	for (d = 0; d < cfg->num_pcm_instances; d++) {
 		struct xen_front_cfg_pcm_instance *pcm_instance;
 		int s, index;

 		pcm_instance = &cfg->pcm_instances[d];

 		for (s = 0; s < pcm_instance->num_streams_pb; s++) {
 			index = pcm_instance->streams_pb[s].index;

 			ret = evtchnl_alloc(front_info, index,
 					    &front_info->evt_pairs[index].req,
 					    EVTCHNL_TYPE_REQ);
 			if (ret < 0) {
 				dev_err(dev, "Error allocating control channel\n");
 				goto fail;
 			}

 			ret = evtchnl_alloc(front_info, index,
 					    &front_info->evt_pairs[index].evt,
 					    EVTCHNL_TYPE_EVT);
 			if (ret < 0) {
 				dev_err(dev, "Error allocating in-event channel\n");
 				goto fail;
 			}
 		}

 		for (s = 0; s < pcm_instance->num_streams_cap; s++) {
 			index = pcm_instance->streams_cap[s].index;

 			ret = evtchnl_alloc(front_info, index,
 					    &front_info->evt_pairs[index].req,
 					    EVTCHNL_TYPE_REQ);
 			if (ret < 0) {
 				dev_err(dev, "Error allocating control channel\n");
 				goto fail;
 			}

 			ret = evtchnl_alloc(front_info, index,
 					    &front_info->evt_pairs[index].evt,
 					    EVTCHNL_TYPE_EVT);
 			if (ret < 0) {
 				dev_err(dev, "Error allocating in-event channel\n");
 				goto fail;
 			}
 		}
 	}

 	front_info->num_evt_pairs = num_streams;
 	return 0;

 fail:
 	xen_snd_front_evtchnl_free_all(front_info);
 	return ret;
 }

 static int evtchnl_publish(struct xenbus_transaction xbt,
 			   struct xen_snd_front_evtchnl *channel,
 			   const char *path, const char *node_ring,
 			   const char *node_chnl)
 {
 	struct xenbus_device *xb_dev = channel->front_info->xb_dev;
 	int ret;

 	/* Write control channel ring reference. */
 	ret = xenbus_printf(xbt, path, node_ring, "%u", channel->gref);
 	if (ret < 0) {
 		dev_err(&xb_dev->dev, "Error writing ring-ref: %d\n", ret);
 		return ret;
 	}

 	/* Write event channel ring reference. */
 	ret = xenbus_printf(xbt, path, node_chnl, "%u", channel->port);
 	if (ret < 0) {
 		dev_err(&xb_dev->dev, "Error writing event channel: %d\n", ret);
 		return ret;
 	}

 	return 0;
 }

 int xen_snd_front_evtchnl_publish_all(struct xen_snd_front_info *front_info)
 {
 	struct xen_front_cfg_card *cfg = &front_info->cfg;
 	struct xenbus_transaction xbt;
 	int ret, d;

 again:
 	ret = xenbus_transaction_start(&xbt);
 	if (ret < 0) {
 		xenbus_dev_fatal(front_info->xb_dev, ret,
 				 "starting transaction");
 		return ret;
 	}

 	for (d = 0; d < cfg->num_pcm_instances; d++) {
 		struct xen_front_cfg_pcm_instance *pcm_instance;
 		int s, index;

 		pcm_instance = &cfg->pcm_instances[d];

 		for (s = 0; s < pcm_instance->num_streams_pb; s++) {
 			index = pcm_instance->streams_pb[s].index;

 			ret = evtchnl_publish(xbt,
 					      &front_info->evt_pairs[index].req,
 					      pcm_instance->streams_pb[s].xenstore_path,
 					      XENSND_FIELD_RING_REF,
 					      XENSND_FIELD_EVT_CHNL);
 			if (ret < 0)
 				goto fail;

 			ret = evtchnl_publish(xbt,
 					      &front_info->evt_pairs[index].evt,
 					      pcm_instance->streams_pb[s].xenstore_path,
 					      XENSND_FIELD_EVT_RING_REF,
 					      XENSND_FIELD_EVT_EVT_CHNL);
 			if (ret < 0)
 				goto fail;
 		}

 		for (s = 0; s < pcm_instance->num_streams_cap; s++) {
 			index = pcm_instance->streams_cap[s].index;

 			ret = evtchnl_publish(xbt,
 					      &front_info->evt_pairs[index].req,
 					      pcm_instance->streams_cap[s].xenstore_path,
 					      XENSND_FIELD_RING_REF,
 					      XENSND_FIELD_EVT_CHNL);
 			if (ret < 0)
 				goto fail;

 			ret = evtchnl_publish(xbt,
 					      &front_info->evt_pairs[index].evt,
 					      pcm_instance->streams_cap[s].xenstore_path,
 					      XENSND_FIELD_EVT_RING_REF,
 					      XENSND_FIELD_EVT_EVT_CHNL);
 			if (ret < 0)
 				goto fail;
 		}
 	}
 	ret = xenbus_transaction_end(xbt, 0);
 	if (ret < 0) {
 		if (ret == -EAGAIN)
 			goto again;

 		xenbus_dev_fatal(front_info->xb_dev, ret,
 				 "completing transaction");
 		goto fail_to_end;
 	}
 	return 0;
 fail:
 	xenbus_transaction_end(xbt, 1);
 fail_to_end:
 	xenbus_dev_fatal(front_info->xb_dev, ret, "writing XenStore");
 	return ret;
 }

 void xen_snd_front_evtchnl_pair_set_connected(struct xen_snd_front_evtchnl_pair *evt_pair,
 					      bool is_connected)
 {
 	enum xen_snd_front_evtchnl_state state;

 	if (is_connected)
 		state = EVTCHNL_STATE_CONNECTED;
 	else
 		state = EVTCHNL_STATE_DISCONNECTED;

 	mutex_lock(&evt_pair->req.ring_io_lock);
 	evt_pair->req.state = state;
 	mutex_unlock(&evt_pair->req.ring_io_lock);

 	mutex_lock(&evt_pair->evt.ring_io_lock);
 	evt_pair->evt.state = state;
 	mutex_unlock(&evt_pair->evt.ring_io_lock);
 }

 void xen_snd_front_evtchnl_pair_clear(struct xen_snd_front_evtchnl_pair *evt_pair)
 {
 	mutex_lock(&evt_pair->req.ring_io_lock);
 	evt_pair->req.evt_next_id = 0;
 	mutex_unlock(&evt_pair->req.ring_io_lock);

 	mutex_lock(&evt_pair->evt.ring_io_lock);
 	evt_pair->evt.evt_next_id = 0;
 	mutex_unlock(&evt_pair->evt.ring_io_lock);
 }
	// SPDX-License-Identifier: GPL-2.0 OR MIT

	/*
	* Xen para-virtual sound device
	*
	* Copyright (C) 2016-2018 EPAM Systems Inc.
	*
	* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
	*/

	#include <xen/events.h>
	#include <xen/grant_table.h>
	#include <xen/xen.h>
	#include <xen/xenbus.h>

	#include "xen_snd_front.h"
	#include "xen_snd_front_alsa.h"
	#include "xen_snd_front_cfg.h"
	#include "xen_snd_front_evtchnl.h"

	static irqreturn_t evtchnl_interrupt_req(int irq, void *dev_id)
	{
	struct xen_snd_front_evtchnl *channel = dev_id;
	struct xen_snd_front_info *front_info = channel->front_info;
	struct xensnd_resp *resp;
	RING_IDX i, rp;

	if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED))
	return IRQ_HANDLED;

	mutex_lock(&channel->ring_io_lock);

	again:
	rp = channel->u.req.ring.sring->rsp_prod;
	/* Ensure we see queued responses up to rp. */
	rmb();

	/*
	* Assume that the backend is trusted to always write sane values
	* to the ring counters, so no overflow checks on frontend side
	* are required.
	*/
	for (i = channel->u.req.ring.rsp_cons; i != rp; i++) {
	resp = RING_GET_RESPONSE(&channel->u.req.ring, i);
	if (resp->id != channel->evt_id)
	continue;
	switch (resp->operation) {
	case XENSND_OP_OPEN:
	case XENSND_OP_CLOSE:
	case XENSND_OP_READ:
	case XENSND_OP_WRITE:
	case XENSND_OP_TRIGGER:
	channel->u.req.resp_status = resp->status;
	complete(&channel->u.req.completion);
	break;
	case XENSND_OP_HW_PARAM_QUERY:
	channel->u.req.resp_status = resp->status;
	channel->u.req.resp.hw_param =
	resp->resp.hw_param;
	complete(&channel->u.req.completion);
	break;

	default:
	dev_err(&front_info->xb_dev->dev,
	"Operation %d is not supported\n",
	resp->operation);
	break;
	}
	}

	channel->u.req.ring.rsp_cons = i;
	if (i != channel->u.req.ring.req_prod_pvt) {
	int more_to_do;

	RING_FINAL_CHECK_FOR_RESPONSES(&channel->u.req.ring,
	more_to_do);
	if (more_to_do)
	goto again;
	} else {
	channel->u.req.ring.sring->rsp_event = i + 1;
	}

	mutex_unlock(&channel->ring_io_lock);
	return IRQ_HANDLED;
	}

	static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
	{
	struct xen_snd_front_evtchnl *channel = dev_id;
	struct xensnd_event_page *page = channel->u.evt.page;
	u32 cons, prod;

	if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED))
	return IRQ_HANDLED;

	mutex_lock(&channel->ring_io_lock);

	prod = page->in_prod;
	/* Ensure we see ring contents up to prod. */
	virt_rmb();
	if (prod == page->in_cons)
	goto out;

	/*
	* Assume that the backend is trusted to always write sane values
	* to the ring counters, so no overflow checks on frontend side
	* are required.
	*/
	for (cons = page->in_cons; cons != prod; cons++) {
	struct xensnd_evt *event;

	event = &XENSND_IN_RING_REF(page, cons);
	if (unlikely(event->id != channel->evt_id++))
	continue;

	switch (event->type) {
	case XENSND_EVT_CUR_POS:
	xen_snd_front_alsa_handle_cur_pos(channel,
	event->op.cur_pos.position);
	break;
	}
	}

	page->in_cons = cons;
	/* Ensure ring contents. */
	virt_wmb();

	out:
	mutex_unlock(&channel->ring_io_lock);
	return IRQ_HANDLED;
	}

	void xen_snd_front_evtchnl_flush(struct xen_snd_front_evtchnl *channel)
	{
	int notify;

	channel->u.req.ring.req_prod_pvt++;
	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&channel->u.req.ring, notify);
	if (notify)
	notify_remote_via_irq(channel->irq);
	}

	static void evtchnl_free(struct xen_snd_front_info *front_info,
	struct xen_snd_front_evtchnl *channel)
	{
	void *page = NULL;

	if (channel->type == EVTCHNL_TYPE_REQ)
	page = channel->u.req.ring.sring;
	else if (channel->type == EVTCHNL_TYPE_EVT)
	page = channel->u.evt.page;

	if (!page)
	return;

	channel->state = EVTCHNL_STATE_DISCONNECTED;
	if (channel->type == EVTCHNL_TYPE_REQ) {
	/* Release all who still waits for response if any. */
	channel->u.req.resp_status = -EIO;
	complete_all(&channel->u.req.completion);
	}

	if (channel->irq)
	unbind_from_irqhandler(channel->irq, channel);

	if (channel->port)
	xenbus_free_evtchn(front_info->xb_dev, channel->port);

	/* End access and free the page. */
	xenbus_teardown_ring(&page, 1, &channel->gref);

	memset(channel, 0, sizeof(*channel));
	}

	void xen_snd_front_evtchnl_free_all(struct xen_snd_front_info *front_info)
	{
	int i;

	if (!front_info->evt_pairs)
	return;

	for (i = 0; i < front_info->num_evt_pairs; i++) {
	evtchnl_free(front_info, &front_info->evt_pairs[i].req);
	evtchnl_free(front_info, &front_info->evt_pairs[i].evt);
	}

	kfree(front_info->evt_pairs);
	front_info->evt_pairs = NULL;
	}

	static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
	struct xen_snd_front_evtchnl *channel,
	enum xen_snd_front_evtchnl_type type)
	{
	struct xenbus_device *xb_dev = front_info->xb_dev;
	void *page;
	irq_handler_t handler;
	char *handler_name = NULL;
	int ret;

	memset(channel, 0, sizeof(*channel));
	channel->type = type;
	channel->index = index;
	channel->front_info = front_info;
	channel->state = EVTCHNL_STATE_DISCONNECTED;
	ret = xenbus_setup_ring(xb_dev, GFP_KERNEL, &page, 1, &channel->gref);
	if (ret)
	goto fail;

	handler_name = kasprintf(GFP_KERNEL, "%s-%s", XENSND_DRIVER_NAME,
	type == EVTCHNL_TYPE_REQ ?
	XENSND_FIELD_RING_REF :
	XENSND_FIELD_EVT_RING_REF);
	if (!handler_name) {
	ret = -ENOMEM;
	goto fail;
	}

	mutex_init(&channel->ring_io_lock);

	if (type == EVTCHNL_TYPE_REQ) {
	struct xen_sndif_sring *sring = page;

	init_completion(&channel->u.req.completion);
	mutex_init(&channel->u.req.req_io_lock);
	XEN_FRONT_RING_INIT(&channel->u.req.ring, sring, XEN_PAGE_SIZE);

	handler = evtchnl_interrupt_req;
	} else {
	channel->u.evt.page = page;
	handler = evtchnl_interrupt_evt;
	}

	ret = xenbus_alloc_evtchn(xb_dev, &channel->port);
	if (ret < 0)
	goto fail;

	ret = bind_evtchn_to_irq(channel->port);
	if (ret < 0) {
	dev_err(&xb_dev->dev,
	"Failed to bind IRQ for domid %d port %d: %d\n",
	front_info->xb_dev->otherend_id, channel->port, ret);
	goto fail;
	}

	channel->irq = ret;

	ret = request_threaded_irq(channel->irq, NULL, handler,
	IRQF_ONESHOT, handler_name, channel);
	if (ret < 0) {
	dev_err(&xb_dev->dev, "Failed to request IRQ %d: %d\n",
	channel->irq, ret);
	goto fail;
	}

	kfree(handler_name);
	return 0;

	fail:
	kfree(handler_name);
	dev_err(&xb_dev->dev, "Failed to allocate ring: %d\n", ret);
	return ret;
	}

	int xen_snd_front_evtchnl_create_all(struct xen_snd_front_info *front_info,
	int num_streams)
	{
	struct xen_front_cfg_card *cfg = &front_info->cfg;
	struct device *dev = &front_info->xb_dev->dev;
	int d, ret = 0;

	front_info->evt_pairs =
	kcalloc(num_streams,
	sizeof(struct xen_snd_front_evtchnl_pair),
	GFP_KERNEL);
	if (!front_info->evt_pairs)
	return -ENOMEM;

	/* Iterate over devices and their streams and create event channels. */
	for (d = 0; d < cfg->num_pcm_instances; d++) {
	struct xen_front_cfg_pcm_instance *pcm_instance;
	int s, index;

	pcm_instance = &cfg->pcm_instances[d];

	for (s = 0; s < pcm_instance->num_streams_pb; s++) {
	index = pcm_instance->streams_pb[s].index;

	ret = evtchnl_alloc(front_info, index,
	&front_info->evt_pairs[index].req,
	EVTCHNL_TYPE_REQ);
	if (ret < 0) {
	dev_err(dev, "Error allocating control channel\n");
	goto fail;
	}

	ret = evtchnl_alloc(front_info, index,
	&front_info->evt_pairs[index].evt,
	EVTCHNL_TYPE_EVT);
	if (ret < 0) {
	dev_err(dev, "Error allocating in-event channel\n");
	goto fail;
	}
	}

	for (s = 0; s < pcm_instance->num_streams_cap; s++) {
	index = pcm_instance->streams_cap[s].index;

	ret = evtchnl_alloc(front_info, index,
	&front_info->evt_pairs[index].req,
	EVTCHNL_TYPE_REQ);
	if (ret < 0) {
	dev_err(dev, "Error allocating control channel\n");
	goto fail;
	}

	ret = evtchnl_alloc(front_info, index,
	&front_info->evt_pairs[index].evt,
	EVTCHNL_TYPE_EVT);
	if (ret < 0) {
	dev_err(dev, "Error allocating in-event channel\n");
	goto fail;
	}
	}
	}

	front_info->num_evt_pairs = num_streams;
	return 0;

	fail:
	xen_snd_front_evtchnl_free_all(front_info);
	return ret;
	}

	static int evtchnl_publish(struct xenbus_transaction xbt,
	struct xen_snd_front_evtchnl *channel,
	const char path, const char node_ring,
	const char *node_chnl)
	{
	struct xenbus_device *xb_dev = channel->front_info->xb_dev;
	int ret;

	/* Write control channel ring reference. */
	ret = xenbus_printf(xbt, path, node_ring, "%u", channel->gref);
	if (ret < 0) {
	dev_err(&xb_dev->dev, "Error writing ring-ref: %d\n", ret);
	return ret;
	}

	/* Write event channel ring reference. */
	ret = xenbus_printf(xbt, path, node_chnl, "%u", channel->port);
	if (ret < 0) {
	dev_err(&xb_dev->dev, "Error writing event channel: %d\n", ret);
	return ret;
	}

	return 0;
	}

	int xen_snd_front_evtchnl_publish_all(struct xen_snd_front_info *front_info)
	{
	struct xen_front_cfg_card *cfg = &front_info->cfg;
	struct xenbus_transaction xbt;
	int ret, d;

	again:
	ret = xenbus_transaction_start(&xbt);
	if (ret < 0) {
	xenbus_dev_fatal(front_info->xb_dev, ret,
	"starting transaction");
	return ret;
	}

	for (d = 0; d < cfg->num_pcm_instances; d++) {
	struct xen_front_cfg_pcm_instance *pcm_instance;
	int s, index;

	pcm_instance = &cfg->pcm_instances[d];

	for (s = 0; s < pcm_instance->num_streams_pb; s++) {
	index = pcm_instance->streams_pb[s].index;

	ret = evtchnl_publish(xbt,
	&front_info->evt_pairs[index].req,
	pcm_instance->streams_pb[s].xenstore_path,
	XENSND_FIELD_RING_REF,
	XENSND_FIELD_EVT_CHNL);
	if (ret < 0)
	goto fail;

	ret = evtchnl_publish(xbt,
	&front_info->evt_pairs[index].evt,
	pcm_instance->streams_pb[s].xenstore_path,
	XENSND_FIELD_EVT_RING_REF,
	XENSND_FIELD_EVT_EVT_CHNL);
	if (ret < 0)
	goto fail;
	}

	for (s = 0; s < pcm_instance->num_streams_cap; s++) {
	index = pcm_instance->streams_cap[s].index;

	ret = evtchnl_publish(xbt,
	&front_info->evt_pairs[index].req,
	pcm_instance->streams_cap[s].xenstore_path,
	XENSND_FIELD_RING_REF,
	XENSND_FIELD_EVT_CHNL);
	if (ret < 0)
	goto fail;

	ret = evtchnl_publish(xbt,
	&front_info->evt_pairs[index].evt,
	pcm_instance->streams_cap[s].xenstore_path,
	XENSND_FIELD_EVT_RING_REF,
	XENSND_FIELD_EVT_EVT_CHNL);
	if (ret < 0)
	goto fail;
	}
	}
	ret = xenbus_transaction_end(xbt, 0);
	if (ret < 0) {
	if (ret == -EAGAIN)
	goto again;

	xenbus_dev_fatal(front_info->xb_dev, ret,
	"completing transaction");
	goto fail_to_end;
	}
	return 0;
	fail:
	xenbus_transaction_end(xbt, 1);
	fail_to_end:
	xenbus_dev_fatal(front_info->xb_dev, ret, "writing XenStore");
	return ret;
	}

	void xen_snd_front_evtchnl_pair_set_connected(struct xen_snd_front_evtchnl_pair *evt_pair,
	bool is_connected)
	{
	enum xen_snd_front_evtchnl_state state;

	if (is_connected)
	state = EVTCHNL_STATE_CONNECTED;
	else
	state = EVTCHNL_STATE_DISCONNECTED;

	mutex_lock(&evt_pair->req.ring_io_lock);
	evt_pair->req.state = state;
	mutex_unlock(&evt_pair->req.ring_io_lock);

	mutex_lock(&evt_pair->evt.ring_io_lock);
	evt_pair->evt.state = state;
	mutex_unlock(&evt_pair->evt.ring_io_lock);
	}

	void xen_snd_front_evtchnl_pair_clear(struct xen_snd_front_evtchnl_pair *evt_pair)
	{
	mutex_lock(&evt_pair->req.ring_io_lock);
	evt_pair->req.evt_next_id = 0;
	mutex_unlock(&evt_pair->req.ring_io_lock);

	mutex_lock(&evt_pair->evt.ring_io_lock);
	evt_pair->evt.evt_next_id = 0;
	mutex_unlock(&evt_pair->evt.ring_io_lock);
	}