[alsa-devel] [Xen-devel][PATCH v3 4/5] sndif: Add explicit back and front synchronization
Oleksandr Andrushchenko
andr2000 at gmail.com
Mon Mar 19 08:22:23 CET 2018
From: Oleksandr Andrushchenko <oleksandr_andrushchenko at epam.com>
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
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko at epam.com>
Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov at epam.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Cc: Takashi Iwai <tiwai at suse.de>
Cc: Takashi Sakamoto <o-takashi at sakamocchi.jp>
Cc: Clemens Ladisch <clemens at ladisch.de>
---
xen/include/public/io/sndif.h | 162 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 161 insertions(+), 1 deletion(-)
diff --git a/xen/include/public/io/sndif.h b/xen/include/public/io/sndif.h
index ec47ff990f2c..be8d7c83fa72 100644
--- a/xen/include/public/io/sndif.h
+++ b/xen/include/public/io/sndif.h
@@ -113,6 +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 ----------------------------
*
@@ -122,6 +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 --------------------------------
*
@@ -135,6 +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 --------------------------------
*
@@ -147,6 +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
@@ -292,6 +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
******************************************************************************
@@ -439,6 +464,19 @@
#define XENSND_OP_GET_VOLUME 5
#define XENSND_OP_MUTE 6
#define XENSND_OP_UNMUTE 7
+#define XENSND_OP_TRIGGER 8
+
+#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
/*
******************************************************************************
@@ -455,6 +493,8 @@
#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"
@@ -566,7 +606,9 @@
* +----------------+----------------+----------------+----------------+
* | gref_directory | 24
* +----------------+----------------+----------------+----------------+
- * | reserved | 28
+ * | period_sz | 28
+ * +----------------+----------------+----------------+----------------+
+ * | reserved | 32
* +----------------+----------------+----------------+----------------+
* |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
* +----------------+----------------+----------------+----------------+
@@ -578,6 +620,14 @@
* 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,
@@ -592,6 +642,7 @@ struct xensnd_open_req {
uint16_t reserved;
uint32_t buffer_sz;
grant_ref_t gref_directory;
+ uint32_t period_sz;
};
/*
@@ -754,8 +805,32 @@ 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 --------------------------------
*
@@ -778,8 +853,51 @@ struct xensnd_rw_req {
* 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
+ *
+ *----------------------------------- 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;
@@ -787,6 +905,7 @@ struct xensnd_req {
union {
struct xensnd_open_req open;
struct xensnd_rw_req rw;
+ struct xensnd_trigger_req trigger;
uint8_t reserved[56];
} op;
};
@@ -799,8 +918,49 @@ struct xensnd_resp {
uint8_t reserved1[56];
};
+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 4096
+#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__ */
/*
--
2.7.4
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