Merge branch 'topic/xen' into for-next

Merge Xen para-virtualized frontend driver from Oleksandr Andrushchenko.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

MAINTAINERS

@@ -15494,6 +15494,13 @@ S:	Supported
 F:	arch/x86/xen/*swiotlb*
 F:	drivers/xen/*swiotlb*
 
+XEN SOUND FRONTEND DRIVER
+M:	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
+L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
+S:	Supported
+F:	sound/xen/*
+
 XFS FILESYSTEM
 M:	Darrick J. Wong <darrick.wong@oracle.com>
 M:	linux-xfs@vger.kernel.org

sound/Kconfig

@@ -96,6 +96,8 @@ source "sound/x86/Kconfig"
 
 source "sound/synth/Kconfig"
 
+source "sound/xen/Kconfig"
+
 endif # SND
 
 endif # !UML

sound/Makefile

@@ -5,7 +5,7 @@
 obj-$(CONFIG_SOUND) += soundcore.o
 obj-$(CONFIG_DMASOUND) += oss/dmasound/
 obj-$(CONFIG_SND) += core/ i2c/ drivers/ isa/ pci/ ppc/ arm/ sh/ synth/ usb/ \
-	firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/
+	firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/ xen/
 obj-$(CONFIG_SND_AOA) += aoa/
 
 # This one must be compilable even if sound is configured out

sound/xen/Kconfig

+# ALSA Xen drivers
+
+config SND_XEN_FRONTEND
+	tristate "Xen para-virtualized sound frontend driver"
+	depends on XEN
+	select SND_PCM
+	select XEN_XENBUS_FRONTEND
+	help
+	  Choose this option if you want to enable a para-virtualized
+	  frontend sound driver for Xen guest OSes.

sound/xen/Makefile

+# SPDX-License-Identifier: GPL-2.0 OR MIT
+
+snd_xen_front-objs := xen_snd_front.o \
+		      xen_snd_front_cfg.o \
+		      xen_snd_front_evtchnl.o \
+		      xen_snd_front_shbuf.o \
+		      xen_snd_front_alsa.o
+
+obj-$(CONFIG_SND_XEN_FRONTEND) += snd_xen_front.o

sound/xen/xen_snd_front.c

+// 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 <linux/delay.h>
+#include <linux/module.h>
+
+#include <xen/page.h>
+#include <xen/platform_pci.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include <xen/interface/io/sndif.h>
+
+#include "xen_snd_front.h"
+#include "xen_snd_front_alsa.h"
+#include "xen_snd_front_evtchnl.h"
+#include "xen_snd_front_shbuf.h"
+
+static struct xensnd_req *
+be_stream_prepare_req(struct xen_snd_front_evtchnl *evtchnl, u8 operation)
+{
+	struct xensnd_req *req;
+
+	req = RING_GET_REQUEST(&evtchnl->u.req.ring,
+			       evtchnl->u.req.ring.req_prod_pvt);
+	req->operation = operation;
+	req->id = evtchnl->evt_next_id++;
+	evtchnl->evt_id = req->id;
+	return req;
+}
+
+static int be_stream_do_io(struct xen_snd_front_evtchnl *evtchnl)
+{
+	if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
+		return -EIO;
+
+	reinit_completion(&evtchnl->u.req.completion);
+	xen_snd_front_evtchnl_flush(evtchnl);
+	return 0;
+}
+
+static int be_stream_wait_io(struct xen_snd_front_evtchnl *evtchnl)
+{
+	if (wait_for_completion_timeout(&evtchnl->u.req.completion,
+			msecs_to_jiffies(VSND_WAIT_BACK_MS)) <= 0)
+		return -ETIMEDOUT;
+
+	return evtchnl->u.req.resp_status;
+}
+
+int xen_snd_front_stream_query_hw_param(struct xen_snd_front_evtchnl *evtchnl,
+					struct xensnd_query_hw_param *hw_param_req,
+					struct xensnd_query_hw_param *hw_param_resp)
+{
+	struct xensnd_req *req;
+	int ret;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	mutex_lock(&evtchnl->ring_io_lock);
+	req = be_stream_prepare_req(evtchnl, XENSND_OP_HW_PARAM_QUERY);
+	req->op.hw_param = *hw_param_req;
+	mutex_unlock(&evtchnl->ring_io_lock);
+
+	ret = be_stream_do_io(evtchnl);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	if (ret == 0)
+		*hw_param_resp = evtchnl->u.req.resp.hw_param;
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_snd_front_stream_prepare(struct xen_snd_front_evtchnl *evtchnl,
+				 struct xen_snd_front_shbuf *sh_buf,
+				 u8 format, unsigned int channels,
+				 unsigned int rate, u32 buffer_sz,
+				 u32 period_sz)
+{
+	struct xensnd_req *req;
+	int ret;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	mutex_lock(&evtchnl->ring_io_lock);
+	req = be_stream_prepare_req(evtchnl, XENSND_OP_OPEN);
+	req->op.open.pcm_format = format;
+	req->op.open.pcm_channels = channels;
+	req->op.open.pcm_rate = rate;
+	req->op.open.buffer_sz = buffer_sz;
+	req->op.open.period_sz = period_sz;
+	req->op.open.gref_directory = xen_snd_front_shbuf_get_dir_start(sh_buf);
+	mutex_unlock(&evtchnl->ring_io_lock);
+
+	ret = be_stream_do_io(evtchnl);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_snd_front_stream_close(struct xen_snd_front_evtchnl *evtchnl)
+{
+	struct xensnd_req *req;
+	int ret;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	mutex_lock(&evtchnl->ring_io_lock);
+	req = be_stream_prepare_req(evtchnl, XENSND_OP_CLOSE);
+	mutex_unlock(&evtchnl->ring_io_lock);
+
+	ret = be_stream_do_io(evtchnl);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_snd_front_stream_write(struct xen_snd_front_evtchnl *evtchnl,
+			       unsigned long pos, unsigned long count)
+{
+	struct xensnd_req *req;
+	int ret;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	mutex_lock(&evtchnl->ring_io_lock);
+	req = be_stream_prepare_req(evtchnl, XENSND_OP_WRITE);
+	req->op.rw.length = count;
+	req->op.rw.offset = pos;
+	mutex_unlock(&evtchnl->ring_io_lock);
+
+	ret = be_stream_do_io(evtchnl);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_snd_front_stream_read(struct xen_snd_front_evtchnl *evtchnl,
+			      unsigned long pos, unsigned long count)
+{
+	struct xensnd_req *req;
+	int ret;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	mutex_lock(&evtchnl->ring_io_lock);
+	req = be_stream_prepare_req(evtchnl, XENSND_OP_READ);
+	req->op.rw.length = count;
+	req->op.rw.offset = pos;
+	mutex_unlock(&evtchnl->ring_io_lock);
+
+	ret = be_stream_do_io(evtchnl);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_snd_front_stream_trigger(struct xen_snd_front_evtchnl *evtchnl,
+				 int type)
+{
+	struct xensnd_req *req;
+	int ret;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	mutex_lock(&evtchnl->ring_io_lock);
+	req = be_stream_prepare_req(evtchnl, XENSND_OP_TRIGGER);
+	req->op.trigger.type = type;
+	mutex_unlock(&evtchnl->ring_io_lock);
+
+	ret = be_stream_do_io(evtchnl);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+static void xen_snd_drv_fini(struct xen_snd_front_info *front_info)
+{
+	xen_snd_front_alsa_fini(front_info);
+	xen_snd_front_evtchnl_free_all(front_info);
+}
+
+static int sndback_initwait(struct xen_snd_front_info *front_info)
+{
+	int num_streams;
+	int ret;
+
+	ret = xen_snd_front_cfg_card(front_info, &num_streams);
+	if (ret < 0)
+		return ret;
+
+	/* create event channels for all streams and publish */
+	ret = xen_snd_front_evtchnl_create_all(front_info, num_streams);
+	if (ret < 0)
+		return ret;
+
+	return xen_snd_front_evtchnl_publish_all(front_info);
+}
+
+static int sndback_connect(struct xen_snd_front_info *front_info)
+{
+	return xen_snd_front_alsa_init(front_info);
+}
+
+static void sndback_disconnect(struct xen_snd_front_info *front_info)
+{
+	xen_snd_drv_fini(front_info);
+	xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
+}
+
+static void sndback_changed(struct xenbus_device *xb_dev,
+			    enum xenbus_state backend_state)
+{
+	struct xen_snd_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
+	int ret;
+
+	dev_dbg(&xb_dev->dev, "Backend state is %s, front is %s\n",
+		xenbus_strstate(backend_state),
+		xenbus_strstate(xb_dev->state));
+
+	switch (backend_state) {
+	case XenbusStateReconfiguring:
+		/* fall through */
+	case XenbusStateReconfigured:
+		/* fall through */
+	case XenbusStateInitialised:
+		/* fall through */
+		break;
+
+	case XenbusStateInitialising:
+		/* Recovering after backend unexpected closure. */
+		sndback_disconnect(front_info);
+		break;
+
+	case XenbusStateInitWait:
+		/* Recovering after backend unexpected closure. */
+		sndback_disconnect(front_info);
+
+		ret = sndback_initwait(front_info);
+		if (ret < 0)
+			xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
+		else
+			xenbus_switch_state(xb_dev, XenbusStateInitialised);
+		break;
+
+	case XenbusStateConnected:
+		if (xb_dev->state != XenbusStateInitialised)
+			break;
+
+		ret = sndback_connect(front_info);
+		if (ret < 0)
+			xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
+		else
+			xenbus_switch_state(xb_dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		/*
+		 * In this state backend starts freeing resources,
+		 * so let it go into closed state first, so we can also
+		 * remove ours.
+		 */
+		break;
+
+	case XenbusStateUnknown:
+		/* fall through */
+	case XenbusStateClosed:
+		if (xb_dev->state == XenbusStateClosed)
+			break;
+
+		sndback_disconnect(front_info);
+		break;
+	}
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+			 const struct xenbus_device_id *id)
+{
+	struct xen_snd_front_info *front_info;
+
+	front_info = devm_kzalloc(&xb_dev->dev,
+				  sizeof(*front_info), GFP_KERNEL);
+	if (!front_info)
+		return -ENOMEM;
+
+	front_info->xb_dev = xb_dev;
+	dev_set_drvdata(&xb_dev->dev, front_info);
+
+	return xenbus_switch_state(xb_dev, XenbusStateInitialising);
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+	struct xen_snd_front_info *front_info = dev_get_drvdata(&dev->dev);
+	int to = 100;
+
+	xenbus_switch_state(dev, XenbusStateClosing);
+
+	/*
+	 * On driver removal it is disconnected from XenBus,
+	 * so no backend state change events come via .otherend_changed
+	 * callback. This prevents us from exiting gracefully, e.g.
+	 * signaling the backend to free event channels, waiting for its
+	 * state to change to XenbusStateClosed and cleaning at our end.
+	 * Normally when front driver removed backend will finally go into
+	 * XenbusStateInitWait state.
+	 *
+	 * Workaround: read backend's state manually and wait with time-out.
+	 */
+	while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
+				     XenbusStateUnknown) != XenbusStateInitWait) &&
+				     to--)
+		msleep(10);
+
+	if (!to) {
+		unsigned int state;
+
+		state = xenbus_read_unsigned(front_info->xb_dev->otherend,
+					     "state", XenbusStateUnknown);
+		pr_err("Backend state is %s while removing driver\n",
+		       xenbus_strstate(state));
+	}
+
+	xen_snd_drv_fini(front_info);
+	xenbus_frontend_closed(dev);
+	return 0;
+}
+
+static const struct xenbus_device_id xen_drv_ids[] = {
+	{ XENSND_DRIVER_NAME },
+	{ "" }
+};
+
+static struct xenbus_driver xen_driver = {
+	.ids = xen_drv_ids,
+	.probe = xen_drv_probe,
+	.remove = xen_drv_remove,
+	.otherend_changed = sndback_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	if (!xen_has_pv_devices())
+		return -ENODEV;
+
+	/* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
+	if (XEN_PAGE_SIZE != PAGE_SIZE) {
+		pr_err(XENSND_DRIVER_NAME ": different kernel and Xen page sizes are not supported: XEN_PAGE_SIZE (%lu) != PAGE_SIZE (%lu)\n",
+		       XEN_PAGE_SIZE, PAGE_SIZE);
+		return -ENODEV;
+	}
+
+	pr_info("Initialising Xen " XENSND_DRIVER_NAME " frontend driver\n");
+	return xenbus_register_frontend(&xen_driver);
+}
+
+static void __exit xen_drv_fini(void)
+{
+	pr_info("Unregistering Xen " XENSND_DRIVER_NAME " frontend driver\n");
+	xenbus_unregister_driver(&xen_driver);
+}
+
+module_init(xen_drv_init);
+module_exit(xen_drv_fini);
+
+MODULE_DESCRIPTION("Xen virtual sound device frontend");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("xen:" XENSND_DRIVER_NAME);
+MODULE_SUPPORTED_DEVICE("{{ALSA,Virtual soundcard}}");

sound/xen/xen_snd_front.h

+/* 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>
+ */
+
+#ifndef __XEN_SND_FRONT_H
+#define __XEN_SND_FRONT_H
+
+#include "xen_snd_front_cfg.h"
+
+struct xen_snd_front_card_info;
+struct xen_snd_front_evtchnl;
+struct xen_snd_front_evtchnl_pair;
+struct xen_snd_front_shbuf;
+struct xensnd_query_hw_param;
+
+struct xen_snd_front_info {
+	struct xenbus_device *xb_dev;
+
+	struct xen_snd_front_card_info *card_info;
+
+	int num_evt_pairs;
+	struct xen_snd_front_evtchnl_pair *evt_pairs;
+
+	struct xen_front_cfg_card cfg;
+};
+
+int xen_snd_front_stream_query_hw_param(struct xen_snd_front_evtchnl *evtchnl,
+					struct xensnd_query_hw_param *hw_param_req,
+					struct xensnd_query_hw_param *hw_param_resp);
+
+int xen_snd_front_stream_prepare(struct xen_snd_front_evtchnl *evtchnl,
+				 struct xen_snd_front_shbuf *sh_buf,
+				 u8 format, unsigned int channels,
+				 unsigned int rate, u32 buffer_sz,
+				 u32 period_sz);
+
+int xen_snd_front_stream_close(struct xen_snd_front_evtchnl *evtchnl);
+
+int xen_snd_front_stream_write(struct xen_snd_front_evtchnl *evtchnl,
+			       unsigned long pos, unsigned long count);
+
+int xen_snd_front_stream_read(struct xen_snd_front_evtchnl *evtchnl,
+			      unsigned long pos, unsigned long count);
+
+int xen_snd_front_stream_trigger(struct xen_snd_front_evtchnl *evtchnl,
+				 int type);
+
+#endif /* __XEN_SND_FRONT_H */

sound/xen/xen_snd_front_alsa.c

+// 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 <linux/platform_device.h>
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.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"
+#include "xen_snd_front_shbuf.h"
+
+struct xen_snd_front_pcm_stream_info {
+	struct xen_snd_front_info *front_info;
+	struct xen_snd_front_evtchnl_pair *evt_pair;
+	struct xen_snd_front_shbuf sh_buf;
+	int index;
+
+	bool is_open;
+	struct snd_pcm_hardware pcm_hw;
+
+	/* Number of processed frames as reported by the backend. */
+	snd_pcm_uframes_t be_cur_frame;
+	/* Current HW pointer to be reported via .period callback. */
+	atomic_t hw_ptr;
+	/* Modulo of the number of processed frames - for period detection. */
+	u32 out_frames;
+};
+
+struct xen_snd_front_pcm_instance_info {
+	struct xen_snd_front_card_info *card_info;
+	struct snd_pcm *pcm;
+	struct snd_pcm_hardware pcm_hw;
+	int num_pcm_streams_pb;
+	struct xen_snd_front_pcm_stream_info *streams_pb;
+	int num_pcm_streams_cap;
+	struct xen_snd_front_pcm_stream_info *streams_cap;
+};
+
+struct xen_snd_front_card_info {
+	struct xen_snd_front_info *front_info;
+	struct snd_card *card;
+	struct snd_pcm_hardware pcm_hw;
+	int num_pcm_instances;
+	struct xen_snd_front_pcm_instance_info *pcm_instances;
+};
+
+struct alsa_sndif_sample_format {
+	u8 sndif;
+	snd_pcm_format_t alsa;
+};
+
+struct alsa_sndif_hw_param {
+	u8 sndif;
+	snd_pcm_hw_param_t alsa;
+};
+
+static const struct alsa_sndif_sample_format ALSA_SNDIF_FORMATS[] = {
+	{
+		.sndif = XENSND_PCM_FORMAT_U8,
+		.alsa = SNDRV_PCM_FORMAT_U8
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S8,
+		.alsa = SNDRV_PCM_FORMAT_S8
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_U16_LE,
+		.alsa = SNDRV_PCM_FORMAT_U16_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_U16_BE,
+		.alsa = SNDRV_PCM_FORMAT_U16_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S16_LE,
+		.alsa = SNDRV_PCM_FORMAT_S16_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S16_BE,
+		.alsa = SNDRV_PCM_FORMAT_S16_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_U24_LE,
+		.alsa = SNDRV_PCM_FORMAT_U24_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_U24_BE,
+		.alsa = SNDRV_PCM_FORMAT_U24_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S24_LE,
+		.alsa = SNDRV_PCM_FORMAT_S24_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S24_BE,
+		.alsa = SNDRV_PCM_FORMAT_S24_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_U32_LE,
+		.alsa = SNDRV_PCM_FORMAT_U32_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_U32_BE,
+		.alsa = SNDRV_PCM_FORMAT_U32_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S32_LE,
+		.alsa = SNDRV_PCM_FORMAT_S32_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_S32_BE,
+		.alsa = SNDRV_PCM_FORMAT_S32_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_A_LAW,
+		.alsa = SNDRV_PCM_FORMAT_A_LAW
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_MU_LAW,
+		.alsa = SNDRV_PCM_FORMAT_MU_LAW
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_F32_LE,
+		.alsa = SNDRV_PCM_FORMAT_FLOAT_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_F32_BE,
+		.alsa = SNDRV_PCM_FORMAT_FLOAT_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_F64_LE,
+		.alsa = SNDRV_PCM_FORMAT_FLOAT64_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_F64_BE,
+		.alsa = SNDRV_PCM_FORMAT_FLOAT64_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE,
+		.alsa = SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE,
+		.alsa = SNDRV_PCM_FORMAT_IEC958_SUBFRAME_BE
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_IMA_ADPCM,
+		.alsa = SNDRV_PCM_FORMAT_IMA_ADPCM
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_MPEG,
+		.alsa = SNDRV_PCM_FORMAT_MPEG
+	},
+	{
+		.sndif = XENSND_PCM_FORMAT_GSM,
+		.alsa = SNDRV_PCM_FORMAT_GSM
+	},
+};
+
+static int to_sndif_format(snd_pcm_format_t format)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
+		if (ALSA_SNDIF_FORMATS[i].alsa == format)
+			return ALSA_SNDIF_FORMATS[i].sndif;
+
+	return -EINVAL;
+}
+
+static u64 to_sndif_formats_mask(u64 alsa_formats)
+{
+	u64 mask;
+	int i;
+
+	mask = 0;
+	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
+		if (1 << ALSA_SNDIF_FORMATS[i].alsa & alsa_formats)
+			mask |= 1 << ALSA_SNDIF_FORMATS[i].sndif;
+
+	return mask;
+}
+
+static u64 to_alsa_formats_mask(u64 sndif_formats)
+{
+	u64 mask;
+	int i;
+
+	mask = 0;
+	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
+		if (1 << ALSA_SNDIF_FORMATS[i].sndif & sndif_formats)
+			mask |= 1 << ALSA_SNDIF_FORMATS[i].alsa;
+
+	return mask;
+}
+
+static void stream_clear(struct xen_snd_front_pcm_stream_info *stream)
+{
+	stream->is_open = false;
+	stream->be_cur_frame = 0;
+	stream->out_frames = 0;
+	atomic_set(&stream->hw_ptr, 0);
+	xen_snd_front_evtchnl_pair_clear(stream->evt_pair);
+	xen_snd_front_shbuf_clear(&stream->sh_buf);
+}
+
+static void stream_free(struct xen_snd_front_pcm_stream_info *stream)
+{
+	xen_snd_front_shbuf_free(&stream->sh_buf);
+	stream_clear(stream);
+}
+
+static struct xen_snd_front_pcm_stream_info *
+stream_get(struct snd_pcm_substream *substream)
+{
+	struct xen_snd_front_pcm_instance_info *pcm_instance =
+			snd_pcm_substream_chip(substream);
+	struct xen_snd_front_pcm_stream_info *stream;
+
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		stream = &pcm_instance->streams_pb[substream->number];
+	else
+		stream = &pcm_instance->streams_cap[substream->number];
+
+	return stream;
+}
+
+static int alsa_hw_rule(struct snd_pcm_hw_params *params,
+			struct snd_pcm_hw_rule *rule)
+{
+	struct xen_snd_front_pcm_stream_info *stream = rule->private;
+	struct device *dev = &stream->front_info->xb_dev->dev;
+	struct snd_mask *formats =
+			hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
+	struct snd_interval *rates =
+			hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
+	struct snd_interval *channels =
+			hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
+	struct snd_interval *period =
+			hw_param_interval(params,
+					  SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
+	struct snd_interval *buffer =
+			hw_param_interval(params,
+					  SNDRV_PCM_HW_PARAM_BUFFER_SIZE);
+	struct xensnd_query_hw_param req;
+	struct xensnd_query_hw_param resp;
+	struct snd_interval interval;
+	struct snd_mask mask;
+	u64 sndif_formats;
+	int changed, ret;
+
+	/* Collect all the values we need for the query. */
+
+	req.formats = to_sndif_formats_mask((u64)formats->bits[0] |
+					    (u64)(formats->bits[1]) << 32);
+
+	req.rates.min = rates->min;
+	req.rates.max = rates->max;
+
+	req.channels.min = channels->min;
+	req.channels.max = channels->max;
+
+	req.buffer.min = buffer->min;
+	req.buffer.max = buffer->max;
+
+	req.period.min = period->min;
+	req.period.max = period->max;
+
+	ret = xen_snd_front_stream_query_hw_param(&stream->evt_pair->req,
+						  &req, &resp);
+	if (ret < 0) {
+		/* Check if this is due to backend communication error. */
+		if (ret == -EIO || ret == -ETIMEDOUT)
+			dev_err(dev, "Failed to query ALSA HW parameters\n");
+		return ret;
+	}
+
+	/* Refine HW parameters after the query. */
+	changed  = 0;
+
+	sndif_formats = to_alsa_formats_mask(resp.formats);
+	snd_mask_none(&mask);
+	mask.bits[0] = (u32)sndif_formats;
+	mask.bits[1] = (u32)(sndif_formats >> 32);
+	ret = snd_mask_refine(formats, &mask);
+	if (ret < 0)
+		return ret;
+	changed |= ret;
+
+	interval.openmin = 0;
+	interval.openmax = 0;
+	interval.integer = 1;
+
+	interval.min = resp.rates.min;
+	interval.max = resp.rates.max;
+	ret = snd_interval_refine(rates, &interval);
+	if (ret < 0)
+		return ret;
+	changed |= ret;
+
+	interval.min = resp.channels.min;
+	interval.max = resp.channels.max;
+	ret = snd_interval_refine(channels, &interval);
+	if (ret < 0)
+		return ret;
+	changed |= ret;
+
+	interval.min = resp.buffer.min;
+	interval.max = resp.buffer.max;
+	ret = snd_interval_refine(buffer, &interval);
+	if (ret < 0)
+		return ret;
+	changed |= ret;
+
+	interval.min = resp.period.min;
+	interval.max = resp.period.max;
+	ret = snd_interval_refine(period, &interval);
+	if (ret < 0)
+		return ret;
+	changed |= ret;
+
+	return changed;
+}
+
+static int alsa_open(struct snd_pcm_substream *substream)
+{
+	struct xen_snd_front_pcm_instance_info *pcm_instance =
+			snd_pcm_substream_chip(substream);
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct xen_snd_front_info *front_info =
+			pcm_instance->card_info->front_info;
+	struct device *dev = &front_info->xb_dev->dev;
+	int ret;
+
+	/*
+	 * Return our HW properties: override defaults with those configured
+	 * via XenStore.
+	 */
+	runtime->hw = stream->pcm_hw;
+	runtime->hw.info &= ~(SNDRV_PCM_INFO_MMAP |
+			      SNDRV_PCM_INFO_MMAP_VALID |
+			      SNDRV_PCM_INFO_DOUBLE |
+			      SNDRV_PCM_INFO_BATCH |
+			      SNDRV_PCM_INFO_NONINTERLEAVED |
+			      SNDRV_PCM_INFO_RESUME |
+			      SNDRV_PCM_INFO_PAUSE);
+	runtime->hw.info |= SNDRV_PCM_INFO_INTERLEAVED;
+
+	stream->evt_pair = &front_info->evt_pairs[stream->index];
+
+	stream->front_info = front_info;
+
+	stream->evt_pair->evt.u.evt.substream = substream;
+
+	stream_clear(stream);
+
+	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, true);
+
+	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
+				  alsa_hw_rule, stream,
+				  SNDRV_PCM_HW_PARAM_FORMAT, -1);
+	if (ret) {
+		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_FORMAT\n");
+		return ret;
+	}
+
+	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
+				  alsa_hw_rule, stream,
+				  SNDRV_PCM_HW_PARAM_RATE, -1);
+	if (ret) {
+		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_RATE\n");
+		return ret;
+	}
+
+	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
+				  alsa_hw_rule, stream,
+				  SNDRV_PCM_HW_PARAM_CHANNELS, -1);
+	if (ret) {
+		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_CHANNELS\n");
+		return ret;
+	}
+
+	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
+				  alsa_hw_rule, stream,
+				  SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
+	if (ret) {
+		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_PERIOD_SIZE\n");
+		return ret;
+	}
+
+	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
+				  alsa_hw_rule, stream,
+				  SNDRV_PCM_HW_PARAM_BUFFER_SIZE, -1);
+	if (ret) {
+		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_BUFFER_SIZE\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int alsa_close(struct snd_pcm_substream *substream)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+
+	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, false);
+	return 0;
+}
+
+static int alsa_hw_params(struct snd_pcm_substream *substream,
+			  struct snd_pcm_hw_params *params)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	int ret;
+
+	/*
+	 * This callback may be called multiple times,
+	 * so free the previously allocated shared buffer if any.
+	 */
+	stream_free(stream);
+
+	ret = xen_snd_front_shbuf_alloc(stream->front_info->xb_dev,
+					&stream->sh_buf,
+					params_buffer_bytes(params));
+	if (ret < 0) {
+		stream_free(stream);
+		dev_err(&stream->front_info->xb_dev->dev,
+			"Failed to allocate buffers for stream with index %d\n",
+			stream->index);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int alsa_hw_free(struct snd_pcm_substream *substream)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	int ret;
+
+	ret = xen_snd_front_stream_close(&stream->evt_pair->req);
+	stream_free(stream);
+	return ret;
+}
+
+static int alsa_prepare(struct snd_pcm_substream *substream)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+
+	if (!stream->is_open) {
+		struct snd_pcm_runtime *runtime = substream->runtime;
+		u8 sndif_format;
+		int ret;
+
+		sndif_format = to_sndif_format(runtime->format);
+		if (sndif_format < 0) {
+			dev_err(&stream->front_info->xb_dev->dev,
+				"Unsupported sample format: %d\n",
+				runtime->format);
+			return sndif_format;
+		}
+
+		ret = xen_snd_front_stream_prepare(&stream->evt_pair->req,
+						   &stream->sh_buf,
+						   sndif_format,
+						   runtime->channels,
+						   runtime->rate,
+						   snd_pcm_lib_buffer_bytes(substream),
+						   snd_pcm_lib_period_bytes(substream));
+		if (ret < 0)
+			return ret;
+
+		stream->is_open = true;
+	}
+
+	return 0;
+}
+
+static int alsa_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	int type;
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+		type = XENSND_OP_TRIGGER_START;
+		break;
+
+	case SNDRV_PCM_TRIGGER_RESUME:
+		type = XENSND_OP_TRIGGER_RESUME;
+		break;
+
+	case SNDRV_PCM_TRIGGER_STOP:
+		type = XENSND_OP_TRIGGER_STOP;
+		break;
+
+	case SNDRV_PCM_TRIGGER_SUSPEND:
+		type = XENSND_OP_TRIGGER_PAUSE;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return xen_snd_front_stream_trigger(&stream->evt_pair->req, type);
+}
+
+void xen_snd_front_alsa_handle_cur_pos(struct xen_snd_front_evtchnl *evtchnl,
+				       u64 pos_bytes)
+{
+	struct snd_pcm_substream *substream = evtchnl->u.evt.substream;
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	snd_pcm_uframes_t delta, new_hw_ptr, cur_frame;
+
+	cur_frame = bytes_to_frames(substream->runtime, pos_bytes);
+
+	delta = cur_frame - stream->be_cur_frame;
+	stream->be_cur_frame = cur_frame;
+
+	new_hw_ptr = (snd_pcm_uframes_t)atomic_read(&stream->hw_ptr);
+	new_hw_ptr = (new_hw_ptr + delta) % substream->runtime->buffer_size;
+	atomic_set(&stream->hw_ptr, (int)new_hw_ptr);
+
+	stream->out_frames += delta;
+	if (stream->out_frames > substream->runtime->period_size) {
+		stream->out_frames %= substream->runtime->period_size;
+		snd_pcm_period_elapsed(substream);
+	}
+}
+
+static snd_pcm_uframes_t alsa_pointer(struct snd_pcm_substream *substream)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+
+	return (snd_pcm_uframes_t)atomic_read(&stream->hw_ptr);
+}
+
+static int alsa_pb_copy_user(struct snd_pcm_substream *substream,
+			     int channel, unsigned long pos, void __user *src,
+			     unsigned long count)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+
+	if (unlikely(pos + count > stream->sh_buf.buffer_sz))
+		return -EINVAL;
+
+	if (copy_from_user(stream->sh_buf.buffer + pos, src, count))
+		return -EFAULT;
+
+	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
+}
+
+static int alsa_pb_copy_kernel(struct snd_pcm_substream *substream,
+			       int channel, unsigned long pos, void *src,
+			       unsigned long count)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+
+	if (unlikely(pos + count > stream->sh_buf.buffer_sz))
+		return -EINVAL;
+
+	memcpy(stream->sh_buf.buffer + pos, src, count);
+
+	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
+}
+
+static int alsa_cap_copy_user(struct snd_pcm_substream *substream,
+			      int channel, unsigned long pos, void __user *dst,
+			      unsigned long count)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	int ret;
+
+	if (unlikely(pos + count > stream->sh_buf.buffer_sz))
+		return -EINVAL;
+
+	ret = xen_snd_front_stream_read(&stream->evt_pair->req, pos, count);
+	if (ret < 0)
+		return ret;
+
+	return copy_to_user(dst, stream->sh_buf.buffer + pos, count) ?
+		-EFAULT : 0;
+}
+
+static int alsa_cap_copy_kernel(struct snd_pcm_substream *substream,
+				int channel, unsigned long pos, void *dst,
+				unsigned long count)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+	int ret;
+
+	if (unlikely(pos + count > stream->sh_buf.buffer_sz))
+		return -EINVAL;
+
+	ret = xen_snd_front_stream_read(&stream->evt_pair->req, pos, count);
+	if (ret < 0)
+		return ret;
+
+	memcpy(dst, stream->sh_buf.buffer + pos, count);
+
+	return 0;
+}
+
+static int alsa_pb_fill_silence(struct snd_pcm_substream *substream,
+				int channel, unsigned long pos,
+				unsigned long count)
+{
+	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
+
+	if (unlikely(pos + count > stream->sh_buf.buffer_sz))
+		return -EINVAL;
+
+	memset(stream->sh_buf.buffer + pos, 0, count);
+
+	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
+}
+
+/*
+ * FIXME: The mmaped data transfer is asynchronous and there is no
+ * ack signal from user-space when it is done. This is the
+ * reason it is not implemented in the PV driver as we do need
+ * to know when the buffer can be transferred to the backend.
+ */
+
+static struct snd_pcm_ops snd_drv_alsa_playback_ops = {
+	.open = alsa_open,
+	.close = alsa_close,
+	.ioctl = snd_pcm_lib_ioctl,
+	.hw_params = alsa_hw_params,
+	.hw_free = alsa_hw_free,
+	.prepare = alsa_prepare,
+	.trigger = alsa_trigger,
+	.pointer = alsa_pointer,
+	.copy_user = alsa_pb_copy_user,
+	.copy_kernel = alsa_pb_copy_kernel,
+	.fill_silence = alsa_pb_fill_silence,
+};
+
+static struct snd_pcm_ops snd_drv_alsa_capture_ops = {
+	.open = alsa_open,
+	.close = alsa_close,
+	.ioctl = snd_pcm_lib_ioctl,
+	.hw_params = alsa_hw_params,
+	.hw_free = alsa_hw_free,
+	.prepare = alsa_prepare,
+	.trigger = alsa_trigger,
+	.pointer = alsa_pointer,
+	.copy_user = alsa_cap_copy_user,
+	.copy_kernel = alsa_cap_copy_kernel,
+};
+
+static int new_pcm_instance(struct xen_snd_front_card_info *card_info,
+			    struct xen_front_cfg_pcm_instance *instance_cfg,
+			    struct xen_snd_front_pcm_instance_info *pcm_instance_info)
+{
+	struct snd_pcm *pcm;
+	int ret, i;
+
+	dev_dbg(&card_info->front_info->xb_dev->dev,
+		"New PCM device \"%s\" with id %d playback %d capture %d",
+		instance_cfg->name,
+		instance_cfg->device_id,
+		instance_cfg->num_streams_pb,
+		instance_cfg->num_streams_cap);
+
+	pcm_instance_info->card_info = card_info;
+
+	pcm_instance_info->pcm_hw = instance_cfg->pcm_hw;
+
+	if (instance_cfg->num_streams_pb) {
+		pcm_instance_info->streams_pb =
+				devm_kcalloc(&card_info->card->card_dev,
+					     instance_cfg->num_streams_pb,
+					     sizeof(struct xen_snd_front_pcm_stream_info),
+					     GFP_KERNEL);
+		if (!pcm_instance_info->streams_pb)
+			return -ENOMEM;
+	}
+
+	if (instance_cfg->num_streams_cap) {
+		pcm_instance_info->streams_cap =
+				devm_kcalloc(&card_info->card->card_dev,
+					     instance_cfg->num_streams_cap,
+					     sizeof(struct xen_snd_front_pcm_stream_info),
+					     GFP_KERNEL);
+		if (!pcm_instance_info->streams_cap)
+			return -ENOMEM;
+	}
+
+	pcm_instance_info->num_pcm_streams_pb =
+			instance_cfg->num_streams_pb;
+	pcm_instance_info->num_pcm_streams_cap =
+			instance_cfg->num_streams_cap;
+
+	for (i = 0; i < pcm_instance_info->num_pcm_streams_pb; i++) {
+		pcm_instance_info->streams_pb[i].pcm_hw =
+			instance_cfg->streams_pb[i].pcm_hw;
+		pcm_instance_info->streams_pb[i].index =
+			instance_cfg->streams_pb[i].index;
+	}
+
+	for (i = 0; i < pcm_instance_info->num_pcm_streams_cap; i++) {
+		pcm_instance_info->streams_cap[i].pcm_hw =
+			instance_cfg->streams_cap[i].pcm_hw;
+		pcm_instance_info->streams_cap[i].index =
+			instance_cfg->streams_cap[i].index;
+	}
+
+	ret = snd_pcm_new(card_info->card, instance_cfg->name,
+			  instance_cfg->device_id,
+			  instance_cfg->num_streams_pb,
+			  instance_cfg->num_streams_cap,
+			  &pcm);
+	if (ret < 0)
+		return ret;
+
+	pcm->private_data = pcm_instance_info;
+	pcm->info_flags = 0;
+	/* we want to handle all PCM operations in non-atomic context */
+	pcm->nonatomic = true;
+	strncpy(pcm->name, "Virtual card PCM", sizeof(pcm->name));
+
+	if (instance_cfg->num_streams_pb)
+		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK,
+				&snd_drv_alsa_playback_ops);
+
+	if (instance_cfg->num_streams_cap)
+		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE,
+				&snd_drv_alsa_capture_ops);
+
+	pcm_instance_info->pcm = pcm;
+	return 0;
+}
+
+int xen_snd_front_alsa_init(struct xen_snd_front_info *front_info)
+{
+	struct device *dev = &front_info->xb_dev->dev;
+	struct xen_front_cfg_card *cfg = &front_info->cfg;
+	struct xen_snd_front_card_info *card_info;
+	struct snd_card *card;
+	int ret, i;
+
+	dev_dbg(dev, "Creating virtual sound card\n");
+
+	ret = snd_card_new(dev, 0, XENSND_DRIVER_NAME, THIS_MODULE,
+			   sizeof(struct xen_snd_front_card_info), &card);
+	if (ret < 0)
+		return ret;
+
+	card_info = card->private_data;
+	card_info->front_info = front_info;
+	front_info->card_info = card_info;
+	card_info->card = card;
+	card_info->pcm_instances =
+			devm_kcalloc(dev, cfg->num_pcm_instances,
+				     sizeof(struct xen_snd_front_pcm_instance_info),
+				     GFP_KERNEL);
+	if (!card_info->pcm_instances) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	card_info->num_pcm_instances = cfg->num_pcm_instances;
+	card_info->pcm_hw = cfg->pcm_hw;
+
+	for (i = 0; i < cfg->num_pcm_instances; i++) {
+		ret = new_pcm_instance(card_info, &cfg->pcm_instances[i],
+				       &card_info->pcm_instances[i]);
+		if (ret < 0)
+			goto fail;
+	}
+
+	strncpy(card->driver, XENSND_DRIVER_NAME, sizeof(card->driver));
+	strncpy(card->shortname, cfg->name_short, sizeof(card->shortname));
+	strncpy(card->longname, cfg->name_long, sizeof(card->longname));
+
+	ret = snd_card_register(card);
+	if (ret < 0)
+		goto fail;
+
+	return 0;
+
+fail:
+	snd_card_free(card);
+	return ret;
+}
+
+void xen_snd_front_alsa_fini(struct xen_snd_front_info *front_info)
+{
+	struct xen_snd_front_card_info *card_info;
+	struct snd_card *card;
+
+	card_info = front_info->card_info;
+	if (!card_info)
+		return;
+
+	card = card_info->card;
+	if (!card)
+		return;
+
+	dev_dbg(&front_info->xb_dev->dev, "Removing virtual sound card %d\n",
+		card->number);
+	snd_card_free(card);
+
+	/* Card_info will be freed when destroying front_info->xb_dev->dev. */
+	card_info->card = NULL;
+}

sound/xen/xen_snd_front_alsa.h

+/* 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>
+ */
+
+#ifndef __XEN_SND_FRONT_ALSA_H
+#define __XEN_SND_FRONT_ALSA_H
+
+struct xen_snd_front_info;
+
+int xen_snd_front_alsa_init(struct xen_snd_front_info *front_info);
+
+void xen_snd_front_alsa_fini(struct xen_snd_front_info *front_info);
+
+void xen_snd_front_alsa_handle_cur_pos(struct xen_snd_front_evtchnl *evtchnl,
+				       u64 pos_bytes);
+
+#endif /* __XEN_SND_FRONT_ALSA_H */

sound/xen/xen_snd_front_cfg.c

+// 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/xenbus.h>
+
+#include <xen/interface/io/sndif.h>
+
+#include "xen_snd_front.h"
+#include "xen_snd_front_cfg.h"
+
+/* Maximum number of supported streams. */
+#define VSND_MAX_STREAM		8
+
+struct cfg_hw_sample_rate {
+	const char *name;
+	unsigned int mask;
+	unsigned int value;
+};
+
+static const struct cfg_hw_sample_rate CFG_HW_SUPPORTED_RATES[] = {
+	{ .name = "5512",   .mask = SNDRV_PCM_RATE_5512,   .value = 5512 },
+	{ .name = "8000",   .mask = SNDRV_PCM_RATE_8000,   .value = 8000 },
+	{ .name = "11025",  .mask = SNDRV_PCM_RATE_11025,  .value = 11025 },
+	{ .name = "16000",  .mask = SNDRV_PCM_RATE_16000,  .value = 16000 },
+	{ .name = "22050",  .mask = SNDRV_PCM_RATE_22050,  .value = 22050 },
+	{ .name = "32000",  .mask = SNDRV_PCM_RATE_32000,  .value = 32000 },
+	{ .name = "44100",  .mask = SNDRV_PCM_RATE_44100,  .value = 44100 },
+	{ .name = "48000",  .mask = SNDRV_PCM_RATE_48000,  .value = 48000 },
+	{ .name = "64000",  .mask = SNDRV_PCM_RATE_64000,  .value = 64000 },
+	{ .name = "96000",  .mask = SNDRV_PCM_RATE_96000,  .value = 96000 },
+	{ .name = "176400", .mask = SNDRV_PCM_RATE_176400, .value = 176400 },
+	{ .name = "192000", .mask = SNDRV_PCM_RATE_192000, .value = 192000 },
+};
+
+struct cfg_hw_sample_format {
+	const char *name;
+	u64 mask;
+};
+
+static const struct cfg_hw_sample_format CFG_HW_SUPPORTED_FORMATS[] = {
+	{
+		.name = XENSND_PCM_FORMAT_U8_STR,
+		.mask = SNDRV_PCM_FMTBIT_U8
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S8_STR,
+		.mask = SNDRV_PCM_FMTBIT_S8
+	},
+	{
+		.name = XENSND_PCM_FORMAT_U16_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_U16_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_U16_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_U16_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S16_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_S16_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S16_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_S16_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_U24_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_U24_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_U24_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_U24_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S24_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_S24_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S24_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_S24_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_U32_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_U32_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_U32_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_U32_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S32_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_S32_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_S32_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_S32_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_A_LAW_STR,
+		.mask = SNDRV_PCM_FMTBIT_A_LAW
+	},
+	{
+		.name = XENSND_PCM_FORMAT_MU_LAW_STR,
+		.mask = SNDRV_PCM_FMTBIT_MU_LAW
+	},
+	{
+		.name = XENSND_PCM_FORMAT_F32_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_FLOAT_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_F32_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_FLOAT_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_F64_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_FLOAT64_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_F64_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_FLOAT64_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR,
+		.mask = SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_LE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR,
+		.mask = SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_BE
+	},
+	{
+		.name = XENSND_PCM_FORMAT_IMA_ADPCM_STR,
+		.mask = SNDRV_PCM_FMTBIT_IMA_ADPCM
+	},
+	{
+		.name = XENSND_PCM_FORMAT_MPEG_STR,
+		.mask = SNDRV_PCM_FMTBIT_MPEG
+	},
+	{
+		.name = XENSND_PCM_FORMAT_GSM_STR,
+		.mask = SNDRV_PCM_FMTBIT_GSM
+	},
+};
+
+static void cfg_hw_rates(char *list, unsigned int len,
+			 const char *path, struct snd_pcm_hardware *pcm_hw)
+{
+	char *cur_rate;
+	unsigned int cur_mask;
+	unsigned int cur_value;
+	unsigned int rates;
+	unsigned int rate_min;
+	unsigned int rate_max;
+	int i;
+
+	rates = 0;
+	rate_min = -1;
+	rate_max = 0;
+	while ((cur_rate = strsep(&list, XENSND_LIST_SEPARATOR))) {
+		for (i = 0; i < ARRAY_SIZE(CFG_HW_SUPPORTED_RATES); i++)
+			if (!strncasecmp(cur_rate,
+					 CFG_HW_SUPPORTED_RATES[i].name,
+					 XENSND_SAMPLE_RATE_MAX_LEN)) {
+				cur_mask = CFG_HW_SUPPORTED_RATES[i].mask;
+				cur_value = CFG_HW_SUPPORTED_RATES[i].value;
+				rates |= cur_mask;
+				if (rate_min > cur_value)
+					rate_min = cur_value;
+				if (rate_max < cur_value)
+					rate_max = cur_value;
+			}
+	}
+
+	if (rates) {
+		pcm_hw->rates = rates;
+		pcm_hw->rate_min = rate_min;
+		pcm_hw->rate_max = rate_max;
+	}
+}
+
+static void cfg_formats(char *list, unsigned int len,
+			const char *path, struct snd_pcm_hardware *pcm_hw)
+{
+	u64 formats;
+	char *cur_format;
+	int i;
+
+	formats = 0;
+	while ((cur_format = strsep(&list, XENSND_LIST_SEPARATOR))) {
+		for (i = 0; i < ARRAY_SIZE(CFG_HW_SUPPORTED_FORMATS); i++)
+			if (!strncasecmp(cur_format,
+					 CFG_HW_SUPPORTED_FORMATS[i].name,
+					 XENSND_SAMPLE_FORMAT_MAX_LEN))
+				formats |= CFG_HW_SUPPORTED_FORMATS[i].mask;
+	}
+
+	if (formats)
+		pcm_hw->formats = formats;
+}
+
+#define MAX_BUFFER_SIZE		(64 * 1024)
+#define MIN_PERIOD_SIZE		64
+#define MAX_PERIOD_SIZE		MAX_BUFFER_SIZE
+#define USE_FORMATS		(SNDRV_PCM_FMTBIT_U8 | \
+				 SNDRV_PCM_FMTBIT_S16_LE)
+#define USE_RATE		(SNDRV_PCM_RATE_CONTINUOUS | \
+				 SNDRV_PCM_RATE_8000_48000)
+#define USE_RATE_MIN		5512
+#define USE_RATE_MAX		48000
+#define USE_CHANNELS_MIN	1
+#define USE_CHANNELS_MAX	2
+#define USE_PERIODS_MIN		2
+#define USE_PERIODS_MAX		(MAX_BUFFER_SIZE / MIN_PERIOD_SIZE)
+
+static const struct snd_pcm_hardware SND_DRV_PCM_HW_DEFAULT = {
+	.info = (SNDRV_PCM_INFO_MMAP |
+		 SNDRV_PCM_INFO_INTERLEAVED |
+		 SNDRV_PCM_INFO_RESUME |
+		 SNDRV_PCM_INFO_MMAP_VALID),
+	.formats = USE_FORMATS,
+	.rates = USE_RATE,
+	.rate_min = USE_RATE_MIN,
+	.rate_max = USE_RATE_MAX,
+	.channels_min = USE_CHANNELS_MIN,
+	.channels_max = USE_CHANNELS_MAX,
+	.buffer_bytes_max = MAX_BUFFER_SIZE,
+	.period_bytes_min = MIN_PERIOD_SIZE,
+	.period_bytes_max = MAX_PERIOD_SIZE,
+	.periods_min = USE_PERIODS_MIN,
+	.periods_max = USE_PERIODS_MAX,
+	.fifo_size = 0,
+};
+
+static void cfg_read_pcm_hw(const char *path,
+			    struct snd_pcm_hardware *parent_pcm_hw,
+			    struct snd_pcm_hardware *pcm_hw)
+{
+	char *list;
+	int val;
+	size_t buf_sz;
+	unsigned int len;
+
+	/* Inherit parent's PCM HW and read overrides from XenStore. */
+	if (parent_pcm_hw)
+		*pcm_hw = *parent_pcm_hw;
+	else
+		*pcm_hw = SND_DRV_PCM_HW_DEFAULT;
+
+	val = xenbus_read_unsigned(path, XENSND_FIELD_CHANNELS_MIN, 0);
+	if (val)
+		pcm_hw->channels_min = val;
+
+	val = xenbus_read_unsigned(path, XENSND_FIELD_CHANNELS_MAX, 0);
+	if (val)
+		pcm_hw->channels_max = val;
+
+	list = xenbus_read(XBT_NIL, path, XENSND_FIELD_SAMPLE_RATES, &len);
+	if (!IS_ERR(list)) {
+		cfg_hw_rates(list, len, path, pcm_hw);
+		kfree(list);
+	}
+
+	list = xenbus_read(XBT_NIL, path, XENSND_FIELD_SAMPLE_FORMATS, &len);
+	if (!IS_ERR(list)) {
+		cfg_formats(list, len, path, pcm_hw);
+		kfree(list);
+	}
+
+	buf_sz = xenbus_read_unsigned(path, XENSND_FIELD_BUFFER_SIZE, 0);
+	if (buf_sz)
+		pcm_hw->buffer_bytes_max = buf_sz;
+
+	/* Update configuration to match new values. */
+	if (pcm_hw->channels_min > pcm_hw->channels_max)
+		pcm_hw->channels_min = pcm_hw->channels_max;
+
+	if (pcm_hw->rate_min > pcm_hw->rate_max)
+		pcm_hw->rate_min = pcm_hw->rate_max;
+
+	pcm_hw->period_bytes_max = pcm_hw->buffer_bytes_max;
+
+	pcm_hw->periods_max = pcm_hw->period_bytes_max /
+		pcm_hw->period_bytes_min;
+}
+
+static int cfg_get_stream_type(const char *path, int index,
+			       int *num_pb, int *num_cap)
+{
+	char *str = NULL;
+	char *stream_path;
+	int ret;
+
+	*num_pb = 0;
+	*num_cap = 0;
+	stream_path = kasprintf(GFP_KERNEL, "%s/%d", path, index);
+	if (!stream_path) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	str = xenbus_read(XBT_NIL, stream_path, XENSND_FIELD_TYPE, NULL);
+	if (IS_ERR(str)) {
+		ret = PTR_ERR(str);
+		goto fail;
+	}
+
+	if (!strncasecmp(str, XENSND_STREAM_TYPE_PLAYBACK,
+			 sizeof(XENSND_STREAM_TYPE_PLAYBACK))) {
+		(*num_pb)++;
+	} else if (!strncasecmp(str, XENSND_STREAM_TYPE_CAPTURE,
+			      sizeof(XENSND_STREAM_TYPE_CAPTURE))) {
+		(*num_cap)++;
+	} else {
+		ret = -EINVAL;
+		goto fail;
+	}
+	ret = 0;
+
+fail:
+	kfree(stream_path);
+	kfree(str);
+	return ret;
+}
+
+static int cfg_stream(struct xen_snd_front_info *front_info,
+		      struct xen_front_cfg_pcm_instance *pcm_instance,
+		      const char *path, int index, int *cur_pb, int *cur_cap,
+		      int *stream_cnt)
+{
+	char *str = NULL;
+	char *stream_path;
+	struct xen_front_cfg_stream *stream;
+	int ret;
+
+	stream_path = devm_kasprintf(&front_info->xb_dev->dev,
+				     GFP_KERNEL, "%s/%d", path, index);
+	if (!stream_path) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	str = xenbus_read(XBT_NIL, stream_path, XENSND_FIELD_TYPE, NULL);
+	if (IS_ERR(str)) {
+		ret = PTR_ERR(str);
+		goto fail;
+	}
+
+	if (!strncasecmp(str, XENSND_STREAM_TYPE_PLAYBACK,
+			 sizeof(XENSND_STREAM_TYPE_PLAYBACK))) {
+		stream = &pcm_instance->streams_pb[(*cur_pb)++];
+	} else if (!strncasecmp(str, XENSND_STREAM_TYPE_CAPTURE,
+			      sizeof(XENSND_STREAM_TYPE_CAPTURE))) {
+		stream = &pcm_instance->streams_cap[(*cur_cap)++];
+	} else {
+		ret = -EINVAL;
+		goto fail;
+	}
+
+	/* Get next stream index. */
+	stream->index = (*stream_cnt)++;
+	stream->xenstore_path = stream_path;
+	/*
+	 * Check XenStore if PCM HW configuration exists for this stream
+	 * and update if so, e.g. we inherit all values from device's PCM HW,
+	 * but can still override some of the values for the stream.
+	 */
+	cfg_read_pcm_hw(stream->xenstore_path,
+			&pcm_instance->pcm_hw, &stream->pcm_hw);
+	ret = 0;
+
+fail:
+	kfree(str);
+	return ret;
+}
+
+static int cfg_device(struct xen_snd_front_info *front_info,
+		      struct xen_front_cfg_pcm_instance *pcm_instance,
+		      struct snd_pcm_hardware *parent_pcm_hw,
+		      const char *path, int node_index, int *stream_cnt)
+{
+	char *str;
+	char *device_path;
+	int ret, i, num_streams;
+	int num_pb, num_cap;
+	int cur_pb, cur_cap;
+	char node[3];
+
+	device_path = kasprintf(GFP_KERNEL, "%s/%d", path, node_index);
+	if (!device_path)
+		return -ENOMEM;
+
+	str = xenbus_read(XBT_NIL, device_path, XENSND_FIELD_DEVICE_NAME, NULL);
+	if (!IS_ERR(str)) {
+		strncpy(pcm_instance->name, str, sizeof(pcm_instance->name));
+		kfree(str);
+	}
+
+	pcm_instance->device_id = node_index;
+
+	/*
+	 * Check XenStore if PCM HW configuration exists for this device
+	 * and update if so, e.g. we inherit all values from card's PCM HW,
+	 * but can still override some of the values for the device.
+	 */
+	cfg_read_pcm_hw(device_path, parent_pcm_hw, &pcm_instance->pcm_hw);
+
+	/* Find out how many streams were configured in Xen store. */
+	num_streams = 0;
+	do {
+		snprintf(node, sizeof(node), "%d", num_streams);
+		if (!xenbus_exists(XBT_NIL, device_path, node))
+			break;
+
+		num_streams++;
+	} while (num_streams < VSND_MAX_STREAM);
+
+	pcm_instance->num_streams_pb = 0;
+	pcm_instance->num_streams_cap = 0;
+	/* Get number of playback and capture streams. */
+	for (i = 0; i < num_streams; i++) {
+		ret = cfg_get_stream_type(device_path, i, &num_pb, &num_cap);
+		if (ret < 0)
+			goto fail;
+
+		pcm_instance->num_streams_pb += num_pb;
+		pcm_instance->num_streams_cap += num_cap;
+	}
+
+	if (pcm_instance->num_streams_pb) {
+		pcm_instance->streams_pb =
+				devm_kcalloc(&front_info->xb_dev->dev,
+					     pcm_instance->num_streams_pb,
+					     sizeof(struct xen_front_cfg_stream),
+					     GFP_KERNEL);
+		if (!pcm_instance->streams_pb) {
+			ret = -ENOMEM;
+			goto fail;
+		}
+	}
+
+	if (pcm_instance->num_streams_cap) {
+		pcm_instance->streams_cap =
+				devm_kcalloc(&front_info->xb_dev->dev,
+					     pcm_instance->num_streams_cap,
+					     sizeof(struct xen_front_cfg_stream),
+					     GFP_KERNEL);
+		if (!pcm_instance->streams_cap) {
+			ret = -ENOMEM;
+			goto fail;
+		}
+	}
+
+	cur_pb = 0;
+	cur_cap = 0;
+	for (i = 0; i < num_streams; i++) {
+		ret = cfg_stream(front_info, pcm_instance, device_path, i,
+				 &cur_pb, &cur_cap, stream_cnt);
+		if (ret < 0)
+			goto fail;
+	}
+	ret = 0;
+
+fail:
+	kfree(device_path);
+	return ret;
+}
+
+int xen_snd_front_cfg_card(struct xen_snd_front_info *front_info,
+			   int *stream_cnt)
+{
+	struct xenbus_device *xb_dev = front_info->xb_dev;
+	struct xen_front_cfg_card *cfg = &front_info->cfg;
+	int ret, num_devices, i;
+	char node[3];
+
+	*stream_cnt = 0;
+	num_devices = 0;
+	do {
+		snprintf(node, sizeof(node), "%d", num_devices);
+		if (!xenbus_exists(XBT_NIL, xb_dev->nodename, node))
+			break;
+
+		num_devices++;
+	} while (num_devices < SNDRV_PCM_DEVICES);
+
+	if (!num_devices) {
+		dev_warn(&xb_dev->dev,
+			 "No devices configured for sound card at %s\n",
+			 xb_dev->nodename);
+		return -ENODEV;
+	}
+
+	/* Start from default PCM HW configuration for the card. */
+	cfg_read_pcm_hw(xb_dev->nodename, NULL, &cfg->pcm_hw);
+
+	cfg->pcm_instances =
+			devm_kcalloc(&front_info->xb_dev->dev, num_devices,
+				     sizeof(struct xen_front_cfg_pcm_instance),
+				     GFP_KERNEL);
+	if (!cfg->pcm_instances)
+		return -ENOMEM;
+
+	for (i = 0; i < num_devices; i++) {
+		ret = cfg_device(front_info, &cfg->pcm_instances[i],
+				 &cfg->pcm_hw, xb_dev->nodename, i, stream_cnt);
+		if (ret < 0)
+			return ret;
+	}
+	cfg->num_pcm_instances = num_devices;
+	return 0;
+}
+

sound/xen/xen_snd_front_cfg.h

+/* 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>
+ */
+
+#ifndef __XEN_SND_FRONT_CFG_H
+#define __XEN_SND_FRONT_CFG_H
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+
+struct xen_snd_front_info;
+
+struct xen_front_cfg_stream {
+	int index;
+	char *xenstore_path;
+	struct snd_pcm_hardware pcm_hw;
+};
+
+struct xen_front_cfg_pcm_instance {
+	char name[80];
+	int device_id;
+	struct snd_pcm_hardware pcm_hw;
+	int  num_streams_pb;
+	struct xen_front_cfg_stream *streams_pb;
+	int  num_streams_cap;
+	struct xen_front_cfg_stream *streams_cap;
+};
+
+struct xen_front_cfg_card {
+	char name_short[32];
+	char name_long[80];
+	struct snd_pcm_hardware pcm_hw;
+	int num_pcm_instances;
+	struct xen_front_cfg_pcm_instance *pcm_instances;
+};
+
+int xen_snd_front_cfg_card(struct xen_snd_front_info *front_info,
+			   int *stream_cnt);
+
+#endif /* __XEN_SND_FRONT_CFG_H */

sound/xen/xen_snd_front_evtchnl.c

+// 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:
+			/* fall through */
+		case XENSND_OP_CLOSE:
+			/* fall through */
+		case XENSND_OP_READ:
+			/* fall through */
+		case XENSND_OP_WRITE:
+			/* fall through */
+		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)
+{
+	unsigned long page = 0;
+
+	if (channel->type == EVTCHNL_TYPE_REQ)
+		page = (unsigned long)channel->u.req.ring.sring;
+	else if (channel->type == EVTCHNL_TYPE_EVT)
+		page = (unsigned long)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. */
+	if (channel->gref != GRANT_INVALID_REF)
+		gnttab_end_foreign_access(channel->gref, 0, page);
+	else
+		free_page(page);
+
+	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;
+	unsigned long page;
+	grant_ref_t gref;
+	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;
+	channel->gref = GRANT_INVALID_REF;
+	page = get_zeroed_page(GFP_KERNEL);
+	if (!page) {
+		ret = -ENOMEM;
+		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 = (struct xen_sndif_sring *)page;
+
+		init_completion(&channel->u.req.completion);
+		mutex_init(&channel->u.req.req_io_lock);
+		SHARED_RING_INIT(sring);
+		FRONT_RING_INIT(&channel->u.req.ring, sring, XEN_PAGE_SIZE);
+
+		ret = xenbus_grant_ring(xb_dev, sring, 1, &gref);
+		if (ret < 0) {
+			channel->u.req.ring.sring = NULL;
+			goto fail;
+		}
+
+		handler = evtchnl_interrupt_req;
+	} else {
+		ret = gnttab_grant_foreign_access(xb_dev->otherend_id,
+						  virt_to_gfn((void *)page), 0);
+		if (ret < 0)
+			goto fail;
+
+		channel->u.evt.page = (struct xensnd_event_page *)page;
+		gref = ret;
+		handler = evtchnl_interrupt_evt;
+	}
+
+	channel->gref = gref;
+
+	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:
+	if (page)
+		free_page(page);
+	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;
+			}
+		}
+	}
+	if (ret < 0)
+		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);
+}
+

sound/xen/xen_snd_front_evtchnl.h

+/* 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>
+ */
+
+#ifndef __XEN_SND_FRONT_EVTCHNL_H
+#define __XEN_SND_FRONT_EVTCHNL_H
+
+#include <xen/interface/io/sndif.h>
+
+struct xen_snd_front_info;
+
+#ifndef GRANT_INVALID_REF
+/*
+ * FIXME: usage of grant reference 0 as invalid grant reference:
+ * grant reference 0 is valid, but never exposed to a PV driver,
+ * because of the fact it is already in use/reserved by the PV console.
+ */
+#define GRANT_INVALID_REF	0
+#endif
+
+/* Timeout in ms to wait for backend to respond. */
+#define VSND_WAIT_BACK_MS	3000
+
+enum xen_snd_front_evtchnl_state {
+	EVTCHNL_STATE_DISCONNECTED,
+	EVTCHNL_STATE_CONNECTED,
+};
+
+enum xen_snd_front_evtchnl_type {
+	EVTCHNL_TYPE_REQ,
+	EVTCHNL_TYPE_EVT,
+};
+
+struct xen_snd_front_evtchnl {
+	struct xen_snd_front_info *front_info;
+	int gref;
+	int port;
+	int irq;
+	int index;
+	/* State of the event channel. */
+	enum xen_snd_front_evtchnl_state state;
+	enum xen_snd_front_evtchnl_type type;
+	/* Either response id or incoming event id. */
+	u16 evt_id;
+	/* Next request id or next expected event id. */
+	u16 evt_next_id;
+	/* Shared ring access lock. */
+	struct mutex ring_io_lock;
+	union {
+		struct {
+			struct xen_sndif_front_ring ring;
+			struct completion completion;
+			/* Serializer for backend IO: request/response. */
+			struct mutex req_io_lock;
+
+			/* Latest response status. */
+			int resp_status;
+			union {
+				struct xensnd_query_hw_param hw_param;
+			} resp;
+		} req;
+		struct {
+			struct xensnd_event_page *page;
+			/* This is needed to handle XENSND_EVT_CUR_POS event. */
+			struct snd_pcm_substream *substream;
+		} evt;
+	} u;
+};
+
+struct xen_snd_front_evtchnl_pair {
+	struct xen_snd_front_evtchnl req;
+	struct xen_snd_front_evtchnl evt;
+};
+
+int xen_snd_front_evtchnl_create_all(struct xen_snd_front_info *front_info,
+				     int num_streams);
+
+void xen_snd_front_evtchnl_free_all(struct xen_snd_front_info *front_info);
+
+int xen_snd_front_evtchnl_publish_all(struct xen_snd_front_info *front_info);
+
+void xen_snd_front_evtchnl_flush(struct xen_snd_front_evtchnl *evtchnl);
+
+void xen_snd_front_evtchnl_pair_set_connected(struct xen_snd_front_evtchnl_pair *evt_pair,
+					      bool is_connected);
+
+void xen_snd_front_evtchnl_pair_clear(struct xen_snd_front_evtchnl_pair *evt_pair);
+
+#endif /* __XEN_SND_FRONT_EVTCHNL_H */

sound/xen/xen_snd_front_shbuf.c

+// 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 <linux/kernel.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include "xen_snd_front_shbuf.h"
+
+grant_ref_t xen_snd_front_shbuf_get_dir_start(struct xen_snd_front_shbuf *buf)
+{
+	if (!buf->grefs)
+		return GRANT_INVALID_REF;
+
+	return buf->grefs[0];
+}
+
+void xen_snd_front_shbuf_clear(struct xen_snd_front_shbuf *buf)
+{
+	memset(buf, 0, sizeof(*buf));
+}
+
+void xen_snd_front_shbuf_free(struct xen_snd_front_shbuf *buf)
+{
+	int i;
+
+	if (buf->grefs) {
+		for (i = 0; i < buf->num_grefs; i++)
+			if (buf->grefs[i] != GRANT_INVALID_REF)
+				gnttab_end_foreign_access(buf->grefs[i],
+							  0, 0UL);
+		kfree(buf->grefs);
+	}
+	kfree(buf->directory);
+	free_pages_exact(buf->buffer, buf->buffer_sz);
+	xen_snd_front_shbuf_clear(buf);
+}
+
+/*
+ * number of grant references a page can hold with respect to the
+ * xensnd_page_directory header
+ */
+#define XENSND_NUM_GREFS_PER_PAGE ((XEN_PAGE_SIZE - \
+		offsetof(struct xensnd_page_directory, gref)) / \
+		sizeof(grant_ref_t))
+
+static void fill_page_dir(struct xen_snd_front_shbuf *buf,
+			  int num_pages_dir)
+{
+	struct xensnd_page_directory *page_dir;
+	unsigned char *ptr;
+	int i, cur_gref, grefs_left, to_copy;
+
+	ptr = buf->directory;
+	grefs_left = buf->num_grefs - num_pages_dir;
+	/*
+	 * skip grant references at the beginning, they are for pages granted
+	 * for the page directory itself
+	 */
+	cur_gref = num_pages_dir;
+	for (i = 0; i < num_pages_dir; i++) {
+		page_dir = (struct xensnd_page_directory *)ptr;
+		if (grefs_left <= XENSND_NUM_GREFS_PER_PAGE) {
+			to_copy = grefs_left;
+			page_dir->gref_dir_next_page = GRANT_INVALID_REF;
+		} else {
+			to_copy = XENSND_NUM_GREFS_PER_PAGE;
+			page_dir->gref_dir_next_page = buf->grefs[i + 1];
+		}
+
+		memcpy(&page_dir->gref, &buf->grefs[cur_gref],
+		       to_copy * sizeof(grant_ref_t));
+
+		ptr += XEN_PAGE_SIZE;
+		grefs_left -= to_copy;
+		cur_gref += to_copy;
+	}
+}
+
+static int grant_references(struct xenbus_device *xb_dev,
+			    struct xen_snd_front_shbuf *buf,
+			    int num_pages_dir, int num_pages_buffer,
+			    int num_grefs)
+{
+	grant_ref_t priv_gref_head;
+	unsigned long frame;
+	int ret, i, j, cur_ref;
+	int otherend_id;
+
+	ret = gnttab_alloc_grant_references(num_grefs, &priv_gref_head);
+	if (ret)
+		return ret;
+
+	buf->num_grefs = num_grefs;
+	otherend_id = xb_dev->otherend_id;
+	j = 0;
+
+	for (i = 0; i < num_pages_dir; i++) {
+		cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+		if (cur_ref < 0) {
+			ret = cur_ref;
+			goto fail;
+		}
+
+		frame = xen_page_to_gfn(virt_to_page(buf->directory +
+						     XEN_PAGE_SIZE * i));
+		gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
+		buf->grefs[j++] = cur_ref;
+	}
+
+	for (i = 0; i < num_pages_buffer; i++) {
+		cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+		if (cur_ref < 0) {
+			ret = cur_ref;
+			goto fail;
+		}
+
+		frame = xen_page_to_gfn(virt_to_page(buf->buffer +
+						     XEN_PAGE_SIZE * i));
+		gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
+		buf->grefs[j++] = cur_ref;
+	}
+
+	gnttab_free_grant_references(priv_gref_head);
+	fill_page_dir(buf, num_pages_dir);
+	return 0;
+
+fail:
+	gnttab_free_grant_references(priv_gref_head);
+	return ret;
+}
+
+static int alloc_int_buffers(struct xen_snd_front_shbuf *buf,
+			     int num_pages_dir, int num_pages_buffer,
+			     int num_grefs)
+{
+	buf->grefs = kcalloc(num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
+	if (!buf->grefs)
+		return -ENOMEM;
+
+	buf->directory = kcalloc(num_pages_dir, XEN_PAGE_SIZE, GFP_KERNEL);
+	if (!buf->directory)
+		goto fail;
+
+	buf->buffer_sz = num_pages_buffer * XEN_PAGE_SIZE;
+	buf->buffer = alloc_pages_exact(buf->buffer_sz, GFP_KERNEL);
+	if (!buf->buffer)
+		goto fail;
+
+	return 0;
+
+fail:
+	kfree(buf->grefs);
+	buf->grefs = NULL;
+	kfree(buf->directory);
+	buf->directory = NULL;
+	return -ENOMEM;
+}
+
+int xen_snd_front_shbuf_alloc(struct xenbus_device *xb_dev,
+			      struct xen_snd_front_shbuf *buf,
+			      unsigned int buffer_sz)
+{
+	int num_pages_buffer, num_pages_dir, num_grefs;
+	int ret;
+
+	xen_snd_front_shbuf_clear(buf);
+
+	num_pages_buffer = DIV_ROUND_UP(buffer_sz, XEN_PAGE_SIZE);
+	/* number of pages the page directory consumes itself */
+	num_pages_dir = DIV_ROUND_UP(num_pages_buffer,
+				     XENSND_NUM_GREFS_PER_PAGE);
+	num_grefs = num_pages_buffer + num_pages_dir;
+
+	ret = alloc_int_buffers(buf, num_pages_dir,
+				num_pages_buffer, num_grefs);
+	if (ret < 0)
+		return ret;
+
+	ret = grant_references(xb_dev, buf, num_pages_dir, num_pages_buffer,
+			       num_grefs);
+	if (ret < 0)
+		return ret;
+
+	fill_page_dir(buf, num_pages_dir);
+	return 0;
+}

sound/xen/xen_snd_front_shbuf.h

+/* 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>
+ */
+
+#ifndef __XEN_SND_FRONT_SHBUF_H
+#define __XEN_SND_FRONT_SHBUF_H
+
+#include <xen/grant_table.h>
+
+#include "xen_snd_front_evtchnl.h"
+
+struct xen_snd_front_shbuf {
+	int num_grefs;
+	grant_ref_t *grefs;
+	u8 *directory;
+	u8 *buffer;
+	size_t buffer_sz;
+};
+
+grant_ref_t xen_snd_front_shbuf_get_dir_start(struct xen_snd_front_shbuf *buf);
+
+int xen_snd_front_shbuf_alloc(struct xenbus_device *xb_dev,
+			      struct xen_snd_front_shbuf *buf,
+			      unsigned int buffer_sz);
+
+void xen_snd_front_shbuf_clear(struct xen_snd_front_shbuf *buf);
+
+void xen_snd_front_shbuf_free(struct xen_snd_front_shbuf *buf);
+
+#endif /* __XEN_SND_FRONT_SHBUF_H */