ALSA: xen-front: Implement ALSA virtual sound driver

Implement essential initialization of the sound driver:
  - introduce required data structures
  - handle driver registration
  - handle sound card registration
  - register sound driver on backend connection
  - remove sound driver on backend disconnect

Initialize virtual sound card with streams according to the
Xen store configuration.

Implement ALSA driver operations including:
  - manage frontend/backend shared buffers
  - manage Xen bus event channel states

Implement requests from front to back for ALSA
PCM operations.
  - report ALSA period elapsed event: handle XENSND_EVT_CUR_POS
    notifications from the backend when stream position advances
    during playback/capture. The event carries a value of how
    many octets were played/captured at the time of the event.
  - implement explicit stream parameter negotiation between
    backend and frontend: handle XENSND_OP_HW_PARAM_QUERY request
    to read/update configuration space for the parameter given:
    request passes desired parameter interval and the response to
    this request returns min/max interval for the parameter to be used.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/xen/Makefile

@@ -3,6 +3,7 @@
 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_shbuf.o \
+		      xen_snd_front_alsa.o
 
 obj-$(CONFIG_SND_XEN_FRONTEND) += snd_xen_front.o

sound/xen/xen_snd_front.c

@@ -19,10 +19,189 @@
 #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);
 }
 
@@ -45,7 +224,7 @@ static int sndback_initwait(struct xen_snd_front_info *front_info)
 
 static int sndback_connect(struct xen_snd_front_info *front_info)
 {
-	return 0;
+	return xen_snd_front_alsa_init(front_info);
 }
 
 static void sndback_disconnect(struct xen_snd_front_info *front_info)

sound/xen/xen_snd_front.h

@@ -13,15 +13,42 @@
 
 #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.h

@@ -0,0 +1,23 @@
+/* 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_evtchnl.c

@@ -14,6 +14,7 @@
 #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"
 
@@ -118,7 +119,8 @@ static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
 
 		switch (event->type) {
 		case XENSND_EVT_CUR_POS:
-			/* Do nothing at the moment. */
+			xen_snd_front_alsa_handle_cur_pos(channel,
+							  event->op.cur_pos.position);
 			break;
 		}
 	}