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Subject: Re: [PATCH v2 5/5] ALSA: xen-front: Implement ALSA virtual sound
 driver
To:     Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org,
        linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
        boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, perex@perex.cz,
        tiwai@suse.com
Cc:     Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
References: <20180416062453.24743-1-andr2000@gmail.com>
 <20180416062453.24743-6-andr2000@gmail.com>
 <f8ec79c7-1b6f-dd00-5bd3-fc9fb8b42de1@suse.com>
From:   Oleksandr Andrushchenko <andr2000@gmail.com>
Message-ID: <e77fe463-68aa-b117-84c5-6dc729a3df42@gmail.com>
Date:   Tue, 17 Apr 2018 14:32:06 +0300
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On 04/16/2018 05:09 PM, Juergen Gross wrote:
> On 16/04/18 08:24, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> 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>
>> ---
>>   sound/xen/Makefile                |   3 +-
>>   sound/xen/xen_snd_front.c         | 193 ++++++++-
>>   sound/xen/xen_snd_front.h         |  28 ++
>>   sound/xen/xen_snd_front_alsa.c    | 830 ++++++++++++++++++++++++++++++++++++++
>>   sound/xen/xen_snd_front_alsa.h    |  23 ++
>>   sound/xen/xen_snd_front_evtchnl.c |   6 +-
>>   6 files changed, 1080 insertions(+), 3 deletions(-)
>>   create mode 100644 sound/xen/xen_snd_front_alsa.c
>>   create mode 100644 sound/xen/xen_snd_front_alsa.h
>>
>> diff --git a/sound/xen/Makefile b/sound/xen/Makefile
>> index f028bc30af5d..1e6470ecc2f2 100644
>> --- a/sound/xen/Makefile
>> +++ b/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
>> diff --git a/sound/xen/xen_snd_front.c b/sound/xen/xen_snd_front.c
>> index 0569c6c596a3..1fef253ea21a 100644
>> --- a/sound/xen/xen_snd_front.c
>> +++ b/sound/xen/xen_snd_front.c
>> @@ -19,10 +19,201 @@
>>   #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 xen_snd_front_info *front_info = evtchnl->front_info;
>> +	struct xensnd_req *req;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	mutex_lock(&evtchnl->u.req.req_io_lock);
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +	req = be_stream_prepare_req(evtchnl, XENSND_OP_HW_PARAM_QUERY);
>> +	req->op.hw_param = *hw_param_req;
>> +
>> +	ret = be_stream_do_io(evtchnl);
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 xen_snd_front_info *front_info = evtchnl->front_info;
>> +	struct xensnd_req *req;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	mutex_lock(&evtchnl->u.req.req_io_lock);
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +	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);
>> +
>> +	ret = be_stream_do_io(evtchnl);
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 xen_snd_front_info *front_info = evtchnl->front_info;
>> +	struct xensnd_req *req;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	mutex_lock(&evtchnl->u.req.req_io_lock);
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +	req = be_stream_prepare_req(evtchnl, XENSND_OP_CLOSE);
>> +
>> +	ret = be_stream_do_io(evtchnl);
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 xen_snd_front_info *front_info = evtchnl->front_info;
>> +	struct xensnd_req *req;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	mutex_lock(&evtchnl->u.req.req_io_lock);
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +	req = be_stream_prepare_req(evtchnl, XENSND_OP_WRITE);
>> +	req->op.rw.length = count;
>> +	req->op.rw.offset = pos;
>> +
>> +	ret = be_stream_do_io(evtchnl);
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 xen_snd_front_info *front_info = evtchnl->front_info;
>> +	struct xensnd_req *req;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	mutex_lock(&evtchnl->u.req.req_io_lock);
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +	req = be_stream_prepare_req(evtchnl, XENSND_OP_READ);
>> +	req->op.rw.length = count;
>> +	req->op.rw.offset = pos;
>> +
>> +	ret = be_stream_do_io(evtchnl);
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 xen_snd_front_info *front_info = evtchnl->front_info;
>> +	struct xensnd_req *req;
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	mutex_lock(&evtchnl->u.req.req_io_lock);
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +	req = be_stream_prepare_req(evtchnl, XENSND_OP_TRIGGER);
>> +	req->op.trigger.type = type;
>> +
>> +	ret = be_stream_do_io(evtchnl);
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 +236,7 @@ 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)
>> diff --git a/sound/xen/xen_snd_front.h b/sound/xen/xen_snd_front.h
>> index 9c2ffbb4e4b8..7adbdb4d2019 100644
>> --- a/sound/xen/xen_snd_front.h
>> +++ b/sound/xen/xen_snd_front.h
>> @@ -13,17 +13,45 @@
>>   
>>   #include "xen_snd_front_cfg.h"
>>   
>> +struct 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 card_info *card_info;
>> +
>>   	/* serializer for backend IO: request/response */
>>   	spinlock_t io_lock;
>> +
>>   	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 */
>> diff --git a/sound/xen/xen_snd_front_alsa.c b/sound/xen/xen_snd_front_alsa.c
>> new file mode 100644
>> index 000000000000..f524b172750e
>> --- /dev/null
>> +++ b/sound/xen/xen_snd_front_alsa.c
>> @@ -0,0 +1,830 @@
>> +// 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 pcm_stream_info {
> Not sure how this is generally handled in the sound drivers, but when
> reviewing the code using those structures I repeatedly tried to find
> their definitions in the sound headers instead of here. Same applies to
> the alsa_* names.
>
> I'd prefer names which don't poison the name space.
I'll try to do something about naming
>> +	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 pcm_instance_info {
>> +	struct card_info *card_info;
>> +	struct snd_pcm *pcm;
>> +	struct snd_pcm_hardware pcm_hw;
>> +	int num_pcm_streams_pb;
>> +	struct pcm_stream_info *streams_pb;
>> +	int num_pcm_streams_cap;
>> +	struct pcm_stream_info *streams_cap;
>> +};
>> +
>> +struct card_info {
>> +	struct xen_snd_front_info *front_info;
>> +	struct snd_card *card;
>> +	struct snd_pcm_hardware pcm_hw;
>> +	int num_pcm_instances;
>> +	struct 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 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 pcm_stream_info *stream)
>> +{
>> +	xen_snd_front_shbuf_free(&stream->sh_buf);
>> +	stream_clear(stream);
>> +}
>> +
>> +static struct pcm_stream_info *stream_get(struct snd_pcm_substream *substream)
>> +{
>> +	struct pcm_instance_info *pcm_instance =
>> +			snd_pcm_substream_chip(substream);
>> +	struct 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 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 pcm_instance_info *pcm_instance =
>> +			snd_pcm_substream_chip(substream);
>> +	struct 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;
>> +	unsigned long flags;
>> +	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;
>> +
>> +	spin_lock_irqsave(&front_info->io_lock, flags);
>> +
>> +	stream->evt_pair = &front_info->evt_pairs[stream->index];
>> +
>> +	stream->front_info = front_info;
>> +
>> +	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, true);
>> +
>> +	stream->evt_pair->evt.u.evt.substream = substream;
>> +
>> +	stream_clear(stream);
>> +
>> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +
>> +	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 pcm_stream_info *stream = stream_get(substream);
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&stream->front_info->io_lock, flags);
>> +
>> +	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, false);
>> +
>> +	spin_unlock_irqrestore(&stream->front_info->io_lock, flags);
>> +	return 0;
>> +}
>> +
>> +static int alsa_hw_params(struct snd_pcm_substream *substream,
>> +			  struct snd_pcm_hw_params *params)
>> +{
>> +	struct 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 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 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 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 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 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 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 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 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 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 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 card_info *card_info,
>> +			    struct xen_front_cfg_pcm_instance *instance_cfg,
>> +			    struct 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 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 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 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 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 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 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;
>> +}
>> diff --git a/sound/xen/xen_snd_front_alsa.h b/sound/xen/xen_snd_front_alsa.h
>> new file mode 100644
>> index 000000000000..18abd9eec967
>> --- /dev/null
>> +++ b/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 */
>> diff --git a/sound/xen/xen_snd_front_evtchnl.c b/sound/xen/xen_snd_front_evtchnl.c
>> index 9ece39f938f8..470196518716 100644
>> --- a/sound/xen/xen_snd_front_evtchnl.c
>> +++ b/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"
>>   
>> @@ -111,7 +112,10 @@ static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
>>   
>>   		switch (event->type) {
>>   		case XENSND_EVT_CUR_POS:
>> -			/* do nothing at the moment */
>> +			spin_unlock_irqrestore(&front_info->io_lock, flags);
>> +			xen_snd_front_alsa_handle_cur_pos(channel,
>> +							  event->op.cur_pos.position);
>> +			spin_lock_irqsave(&front_info->io_lock, flags);
> Is this correct? Why can you free the lock here without doing any
> harm? What is the lock protecting? I'd like to see at least some
> comments explaining why the lock is needed and why it can be dropped
> here.
Well, this code has issues and will be re-worked:
1. Which locks I need:
1.1. lock to serialize requests to backend
1.2. lock to protect the ring: between requests code and interrupt handler

2. I don't really need a spinlock here b/c interrupts are threaded,
so I can safely use a mutex: thus no need for fancy code with unlocking
and locking again while servicing xen_snd_front_alsa_handle_cur_pos

Thank you
>
> Juergen