This is the sync up with the canonical definition of the sound
protocol in Xen:

1. Protocol version was referenced in the protocol description,
   but missed its definition. Fixed by adding a constant
   for current protocol version.

2. Some of the request descriptions have "reserved" fields
   missed: fixed by adding corresponding entries.

3. Extend the size of the requests and responses to 64 octets.
   Bump protocol version to 2.

4. Add explicit back and front synchronization
   In order to provide explicit synchronization between backend and
   frontend the following changes are introduced in the protocol:
    - add new ring buffer for sending asynchronous events from
      backend to frontend to report number of bytes played by the
      frontend (XENSND_EVT_CUR_POS)
    - introduce trigger events for playback control: start/stop/pause/resume
    - add "req-" prefix to event-channel and ring-ref to unify naming
      of the Xen event channels for requests and events

5. Add explicit back and front parameter negotiation
   In order to provide explicit stream parameter negotiation between
   backend and frontend the following changes are introduced in the protocol:
   add XENSND_OP_HW_PARAM_QUERY request to read/update
   configuration space for the parameters given: request passes
   desired parameter's intervals/masks and the response to this request
   returns allowed min/max intervals/masks to be used.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
Signed-off-by: Oleksandr Grytsov <oleksandr_gryt...@epam.com>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Takashi Iwai <ti...@suse.de>
---
 include/xen/interface/io/sndif.h | 322 +++++++++++++++++++++++++++++--
 1 file changed, 306 insertions(+), 16 deletions(-)

diff --git a/include/xen/interface/io/sndif.h b/include/xen/interface/io/sndif.h
index 5c918276835e..78bb5d9f8d83 100644
--- a/include/xen/interface/io/sndif.h
+++ b/include/xen/interface/io/sndif.h
@@ -36,6 +36,13 @@
 #include "ring.h"
 #include "../grant_table.h"
 
+/*
+ ******************************************************************************
+ *                           Protocol version
+ ******************************************************************************
+ */
+#define XENSND_PROTOCOL_VERSION        2
+
 /*
  ******************************************************************************
  *                  Feature and Parameter Negotiation
@@ -106,6 +113,8 @@
  *
  * /local/domain/1/device/vsnd/0/0/0/ring-ref = "386"
  * /local/domain/1/device/vsnd/0/0/0/event-channel = "15"
+ * /local/domain/1/device/vsnd/0/0/0/evt-ring-ref = "1386"
+ * /local/domain/1/device/vsnd/0/0/0/evt-event-channel = "215"
  *
  *------------------------------ Stream 1, capture ----------------------------
  *
@@ -115,6 +124,8 @@
  *
  * /local/domain/1/device/vsnd/0/0/1/ring-ref = "384"
  * /local/domain/1/device/vsnd/0/0/1/event-channel = "13"
+ * /local/domain/1/device/vsnd/0/0/1/evt-ring-ref = "1384"
+ * /local/domain/1/device/vsnd/0/0/1/evt-event-channel = "213"
  *
  *------------------------------- PCM device 1 --------------------------------
  *
@@ -128,6 +139,8 @@
  *
  * /local/domain/1/device/vsnd/0/1/0/ring-ref = "387"
  * /local/domain/1/device/vsnd/0/1/0/event-channel = "151"
+ * /local/domain/1/device/vsnd/0/1/0/evt-ring-ref = "1387"
+ * /local/domain/1/device/vsnd/0/1/0/evt-event-channel = "351"
  *
  *------------------------------- PCM device 2 --------------------------------
  *
@@ -140,6 +153,8 @@
  *
  * /local/domain/1/device/vsnd/0/2/0/ring-ref = "389"
  * /local/domain/1/device/vsnd/0/2/0/event-channel = "152"
+ * /local/domain/1/device/vsnd/0/2/0/evt-ring-ref = "1389"
+ * /local/domain/1/device/vsnd/0/2/0/evt-event-channel = "452"
  *
  ******************************************************************************
  *                            Backend XenBus Nodes
@@ -285,6 +300,23 @@
  *      The Xen grant reference granting permission for the backend to map
  *      a sole page in a single page sized ring buffer.
  *
+ *--------------------- Stream Event Transport Parameters ---------------------
+ *
+ * This communication path is used to deliver asynchronous events from backend
+ * to frontend, set up per stream.
+ *
+ * evt-event-channel
+ *      Values:         <uint32_t>
+ *
+ *      The identifier of the Xen event channel used to signal activity
+ *      in the ring buffer.
+ *
+ * evt-ring-ref
+ *      Values:         <uint32_t>
+ *
+ *      The Xen grant reference granting permission for the backend to map
+ *      a sole page in a single page sized ring buffer.
+ *
  ******************************************************************************
  *                               STATE DIAGRAMS
  ******************************************************************************
@@ -432,6 +464,20 @@
 #define XENSND_OP_GET_VOLUME           5
 #define XENSND_OP_MUTE                 6
 #define XENSND_OP_UNMUTE               7
+#define XENSND_OP_TRIGGER              8
+#define XENSND_OP_HW_PARAM_QUERY       9
+
+#define XENSND_OP_TRIGGER_START                0
+#define XENSND_OP_TRIGGER_PAUSE                1
+#define XENSND_OP_TRIGGER_STOP         2
+#define XENSND_OP_TRIGGER_RESUME       3
+
+/*
+ ******************************************************************************
+ *                                 EVENT CODES
+ ******************************************************************************
+ */
+#define XENSND_EVT_CUR_POS             0
 
 /*
  ******************************************************************************
@@ -448,6 +494,8 @@
 #define XENSND_FIELD_VCARD_LONG_NAME   "long-name"
 #define XENSND_FIELD_RING_REF          "ring-ref"
 #define XENSND_FIELD_EVT_CHNL          "event-channel"
+#define XENSND_FIELD_EVT_RING_REF      "evt-ring-ref"
+#define XENSND_FIELD_EVT_EVT_CHNL      "evt-event-channel"
 #define XENSND_FIELD_DEVICE_NAME       "name"
 #define XENSND_FIELD_TYPE              "type"
 #define XENSND_FIELD_STREAM_UNIQUE_ID  "unique-id"
@@ -526,7 +574,7 @@
  *
  *---------------------------------- Requests ---------------------------------
  *
- * All request packets have the same length (32 octets)
+ * All request packets have the same length (64 octets)
  * All request packets have common header:
  *         0                1                 2               3        octet
  * +----------------+----------------+----------------+----------------+
@@ -559,11 +607,13 @@
  * +----------------+----------------+----------------+----------------+
  * |                           gref_directory                          | 24
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 28
+ * |                             period_sz                             | 28
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 32
  * +----------------+----------------+----------------+----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 32
+ * |                             reserved                              | 64
  * +----------------+----------------+----------------+----------------+
  *
  * pcm_rate - uint32_t, stream data rate, Hz
@@ -571,6 +621,14 @@
  * pcm_channels - uint8_t, number of channels of this stream,
  *   [channels-min; channels-max]
  * buffer_sz - uint32_t, buffer size to be allocated, octets
+ * period_sz - uint32_t, event period size, octets
+ *   This is the requested value of the period at which frontend would
+ *   like to receive XENSND_EVT_CUR_POS notifications from the backend when
+ *   stream position advances during playback/capture.
+ *   It shows how many octets are expected to be played/captured before
+ *   sending such an event.
+ *   If set to 0 no XENSND_EVT_CUR_POS events are sent by the backend.
+ *
  * gref_directory - grant_ref_t, a reference to the first shared page
  *   describing shared buffer references. At least one page exists. If shared
  *   buffer size  (buffer_sz) exceeds what can be addressed by this single 
page,
@@ -585,6 +643,7 @@ struct xensnd_open_req {
        uint16_t reserved;
        uint32_t buffer_sz;
        grant_ref_t gref_directory;
+       uint32_t period_sz;
 };
 
 /*
@@ -632,7 +691,7 @@ struct xensnd_page_directory {
  * +----------------+----------------+----------------+----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 32
+ * |                             reserved                              | 64
  * +----------------+----------------+----------------+----------------+
  *
  * Request read/write - used for read (for capture) or write (for playback):
@@ -650,7 +709,7 @@ struct xensnd_page_directory {
  * +----------------+----------------+----------------+----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 32
+ * |                             reserved                              | 64
  * +----------------+----------------+----------------+----------------+
  *
  * operation - XENSND_OP_READ for read or XENSND_OP_WRITE for write
@@ -673,9 +732,11 @@ struct xensnd_rw_req {
  * +----------------+----------------+----------------+----------------+
  * |                              length                               | 16
  * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 20
+ * +----------------+----------------+----------------+----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 32
+ * |                             reserved                              | 64
  * +----------------+----------------+----------------+----------------+
  *
  * operation - XENSND_OP_SET_VOLUME for volume set
@@ -713,9 +774,11 @@ struct xensnd_rw_req {
  * +----------------+----------------+----------------+----------------+
  * |                              length                               | 16
  * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 20
+ * +----------------+----------------+----------------+----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 32
+ * |                             reserved                              | 64
  * +----------------+----------------+----------------+----------------+
  *
  * operation - XENSND_OP_MUTE for mute or XENSND_OP_UNMUTE for unmute
@@ -743,32 +806,213 @@ struct xensnd_rw_req {
  *
  * The 'struct xensnd_rw_req' is also used for XENSND_OP_SET_VOLUME,
  * XENSND_OP_GET_VOLUME, XENSND_OP_MUTE, XENSND_OP_UNMUTE.
+ *
+ * Request stream running state change - trigger PCM stream running state
+ * to start, stop, pause or resume:
+ *
+ *         0                1                 2               3        octet
+ * +----------------+----------------+----------------+----------------+
+ * |               id                |   _OP_TRIGGER  |    reserved    | 4
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 8
+ * +----------------+----------------+----------------+----------------+
+ * |      type      |                     reserved                     | 12
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 16
+ * +----------------+----------------+----------------+----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 64
+ * +----------------+----------------+----------------+----------------+
+ *
+ * type - uint8_t, XENSND_OP_TRIGGER_XXX value
  */
 
+struct xensnd_trigger_req {
+       uint8_t type;
+};
+
 /*
- *---------------------------------- Responses --------------------------------
+ * Request stream parameter ranges: request intervals and
+ *   masks of supported ranges for stream configuration values.
  *
- * All response packets have the same length (32 octets)
+ *   Sound device configuration for a particular stream is a limited subset
+ *   of the multidimensional configuration available on XenStore, e.g.
+ *   once the frame rate has been selected there is a limited supported range
+ *   for sample rates becomes available (which might be the same set configured
+ *   on XenStore or less). For example, selecting 96kHz sample rate may limit
+ *   number of channels available for such configuration from 4 to 2, etc.
+ *   Thus, each call to XENSND_OP_HW_PARAM_QUERY may reduce configuration
+ *   space making it possible to iteratively get the final stream 
configuration,
+ *   used in XENSND_OP_OPEN request.
+ *
+ *   See response format for this request.
  *
- * Response for all requests:
  *         0                1                 2               3        octet
  * +----------------+----------------+----------------+----------------+
- * |               id                |    operation   |    reserved    | 4
+ * |               id                | _HW_PARAM_QUERY|    reserved    | 4
  * +----------------+----------------+----------------+----------------+
- * |                              status                               | 8
+ * |                             reserved                              | 8
+ * +----------------+----------------+----------------+----------------+
+ * |                     formats mask low 32-bit                       | 12
+ * +----------------+----------------+----------------+----------------+
+ * |                     formats mask high 32-bit                      | 16
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 12
+ * |                              min rate                             | 20
+ * +----------------+----------------+----------------+----------------+
+ * |                              max rate                             | 24
+ * +----------------+----------------+----------------+----------------+
+ * |                            min channels                           | 28
+ * +----------------+----------------+----------------+----------------+
+ * |                            max channels                           | 32
+ * +----------------+----------------+----------------+----------------+
+ * |                         min buffer frames                         | 36
+ * +----------------+----------------+----------------+----------------+
+ * |                         max buffer frames                         | 40
+ * +----------------+----------------+----------------+----------------+
+ * |                         min period frames                         | 44
+ * +----------------+----------------+----------------+----------------+
+ * |                         max period frames                         | 48
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 52
  * +----------------+----------------+----------------+----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
  * +----------------+----------------+----------------+----------------+
- * |                             reserved                              | 32
+ * |                             reserved                              | 64
+ * +----------------+----------------+----------------+----------------+
+ *
+ * formats - uint64_t, bit mask representing values of the parameter
+ *     made as bitwise OR of (1 << XENSND_PCM_FORMAT_XXX) values
+ *
+ * For interval parameters:
+ *   min - uint32_t, minimum value of the parameter
+ *   max - uint32_t, maximum value of the parameter
+ *
+ * Frame is defined as a product of the number of channels by the
+ * number of octets per one sample.
+ */
+
+struct xensnd_query_hw_param {
+       uint64_t formats;
+       struct {
+               uint32_t min;
+               uint32_t max;
+       } rates;
+       struct {
+               uint32_t min;
+               uint32_t max;
+       } channels;
+       struct {
+               uint32_t min;
+               uint32_t max;
+       } buffer;
+       struct {
+               uint32_t min;
+               uint32_t max;
+       } period;
+};
+
+/*
+ *---------------------------------- Responses --------------------------------
+ *
+ * All response packets have the same length (64 octets)
+ *
+ * All response packets have common header:
+ *         0                1                 2               3        octet
+ * +----------------+----------------+----------------+----------------+
+ * |               id                |    operation   |    reserved    | 4
+ * +----------------+----------------+----------------+----------------+
+ * |                              status                               | 8
  * +----------------+----------------+----------------+----------------+
  *
  * id - uint16_t, copied from the request
  * operation - uint8_t, XENSND_OP_* - copied from request
  * status - int32_t, response status, zero on success and -XEN_EXX on failure
+ *
+ *
+ * HW parameter query response - response for XENSND_OP_HW_PARAM_QUERY:
+ *         0                1                 2               3        octet
+ * +----------------+----------------+----------------+----------------+
+ * |               id                |    operation   |    reserved    | 4
+ * +----------------+----------------+----------------+----------------+
+ * |                              status                               | 8
+ * +----------------+----------------+----------------+----------------+
+ * |                     formats mask low 32-bit                       | 12
+ * +----------------+----------------+----------------+----------------+
+ * |                     formats mask high 32-bit                      | 16
+ * +----------------+----------------+----------------+----------------+
+ * |                              min rate                             | 20
+ * +----------------+----------------+----------------+----------------+
+ * |                              max rate                             | 24
+ * +----------------+----------------+----------------+----------------+
+ * |                            min channels                           | 28
+ * +----------------+----------------+----------------+----------------+
+ * |                            max channels                           | 32
+ * +----------------+----------------+----------------+----------------+
+ * |                         min buffer frames                         | 36
+ * +----------------+----------------+----------------+----------------+
+ * |                         max buffer frames                         | 40
+ * +----------------+----------------+----------------+----------------+
+ * |                         min period frames                         | 44
+ * +----------------+----------------+----------------+----------------+
+ * |                         max period frames                         | 48
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 52
+ * +----------------+----------------+----------------+----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 64
+ * +----------------+----------------+----------------+----------------+
+ *
+ * Meaning of the values in this response is the same as for
+ * XENSND_OP_HW_PARAM_QUERY request.
+ */
+
+/*
+ *----------------------------------- Events ----------------------------------
+ *
+ * Events are sent via shared page allocated by the front and propagated by
+ *   evt-event-channel/evt-ring-ref XenStore entries
+ * All event packets have the same length (64 octets)
+ * All event packets have common header:
+ *         0                1                 2               3        octet
+ * +----------------+----------------+----------------+----------------+
+ * |               id                |      type      |   reserved     | 4
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 8
+ * +----------------+----------------+----------------+----------------+
+ *
+ * id - uint16_t, event id, may be used by front
+ * type - uint8_t, type of the event
+ *
+ *
+ * Current stream position - event from back to front when stream's
+ *   playback/capture position has advanced:
+ *         0                1                 2               3        octet
+ * +----------------+----------------+----------------+----------------+
+ * |               id                |   _EVT_CUR_POS |   reserved     | 4
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 8
+ * +----------------+----------------+----------------+----------------+
+ * |                         position low 32-bit                       | 12
+ * +----------------+----------------+----------------+----------------+
+ * |                         position high 32-bit                      | 16
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 20
+ * +----------------+----------------+----------------+----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +----------------+----------------+----------------+----------------+
+ * |                             reserved                              | 64
+ * +----------------+----------------+----------------+----------------+
+ *
+ * position - current value of stream's playback/capture position, octets
+ *
  */
 
+struct xensnd_cur_pos_evt {
+       uint64_t position;
+};
+
 struct xensnd_req {
        uint16_t id;
        uint8_t operation;
@@ -776,7 +1020,9 @@ struct xensnd_req {
        union {
                struct xensnd_open_req open;
                struct xensnd_rw_req rw;
-               uint8_t reserved[24];
+               struct xensnd_trigger_req trigger;
+               struct xensnd_query_hw_param hw_param;
+               uint8_t reserved[56];
        } op;
 };
 
@@ -785,9 +1031,53 @@ struct xensnd_resp {
        uint8_t operation;
        uint8_t reserved;
        int32_t status;
-       uint8_t reserved1[24];
+       union {
+               struct xensnd_query_hw_param hw_param;
+               uint8_t reserved1[56];
+       } resp;
+};
+
+struct xensnd_evt {
+       uint16_t id;
+       uint8_t type;
+       uint8_t reserved[5];
+       union {
+               struct xensnd_cur_pos_evt cur_pos;
+               uint8_t reserved[56];
+       } op;
 };
 
 DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);
 
+/*
+ ******************************************************************************
+ *                        Back to front events delivery
+ ******************************************************************************
+ * In order to deliver asynchronous events from back to front a shared page is
+ * allocated by front and its granted reference propagated to back via
+ * XenStore entries (evt-ring-ref/evt-event-channel).
+ * This page has a common header used by both front and back to synchronize
+ * access and control event's ring buffer, while back being a producer of the
+ * events and front being a consumer. The rest of the page after the header
+ * is used for event packets.
+ *
+ * Upon reception of an event(s) front may confirm its reception
+ * for either each event, group of events or none.
+ */
+
+struct xensnd_event_page {
+       uint32_t in_cons;
+       uint32_t in_prod;
+       uint8_t reserved[56];
+};
+
+#define XENSND_EVENT_PAGE_SIZE XEN_PAGE_SIZE
+#define XENSND_IN_RING_OFFS (sizeof(struct xensnd_event_page))
+#define XENSND_IN_RING_SIZE (XENSND_EVENT_PAGE_SIZE - XENSND_IN_RING_OFFS)
+#define XENSND_IN_RING_LEN (XENSND_IN_RING_SIZE / sizeof(struct xensnd_evt))
+#define XENSND_IN_RING(page) \
+       ((struct xensnd_evt *)((char *)(page) + XENSND_IN_RING_OFFS))
+#define XENSND_IN_RING_REF(page, idx) \
+       (XENSND_IN_RING((page))[(idx) % XENSND_IN_RING_LEN])
+
 #endif /* __XEN_PUBLIC_IO_SNDIF_H__ */
-- 
2.17.0


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