[pulseaudio-discuss] [PATCH 10/11] Protocol, client: Add commands to enable ringbuffer

[David Henningsson]

This increments protocol version to v30 and adds two new commands
to enable and disable an shm ringbuffer, as well as client side
implementation.

Signed-off-by: David Henningsson <david.henningsson at canonical.com>
---
 PROTOCOL                      | 15 +++++++++++
 configure.ac                  |  2 +-
 src/pulse/context.c           | 58 ++++++++++++++++++++++++++++++++++++++++++-
 src/pulsecore/native-common.h |  4 +++
 4 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/PROTOCOL b/PROTOCOL
index 850b953..9aeeecb 100644
--- a/PROTOCOL
+++ b/PROTOCOL
@@ -351,6 +351,21 @@ New field in all commands that send/receive profile introspection data
 
 The field is added once for every profile.
 
+## v30, implemented by >= 6.0
+#
+A new protocol mechanism supported: Two ringbuffers in shared memory.
+Pulseaudio fdsem (wrappers around event file descriptors) are used for
+signalling new data.
+The protocol has a new SHM flag telling whether a SHM memblock is writable
+by both sides.
+
+PA_COMMAND_ENABLE_RINGBUFFER
+Tells the client to start listening on the additional SHM ringbuffer channel.
+This command also has ancillary data (two eventfds attached to it).
+
+PA_COMMAND_DISABLE_RINGBUFFER
+Tells the client to stop listening on the additional SHM ringbuffer channel.
+
 #### If you just changed the protocol, read this
 ## module-tunnel depends on the sink/source/sink-input/source-input protocol
 ## internals, so if you changed these, you might have broken module-tunnel.
diff --git a/configure.ac b/configure.ac
index e75973f..b7aeef9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,7 +41,7 @@ AC_SUBST(PA_MINOR, pa_minor)
 AC_SUBST(PA_MAJORMINOR, pa_major.pa_minor)
 
 AC_SUBST(PA_API_VERSION, 12)
-AC_SUBST(PA_PROTOCOL_VERSION, 29)
+AC_SUBST(PA_PROTOCOL_VERSION, 30)
 
 # The stable ABI for client applications, for the version info x:y:z
 # always will hold y=z
diff --git a/src/pulse/context.c b/src/pulse/context.c
index 7456ee5..5cde5be 100644
--- a/src/pulse/context.c
+++ b/src/pulse/context.c
@@ -72,6 +72,8 @@
 #include "context.h"
 
 void pa_command_extension(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata);
+static void pa_command_enable_ringbuffer(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata);
+static void pa_command_disable_ringbuffer(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata);
 
 static const pa_pdispatch_cb_t command_table[PA_COMMAND_MAX] = {
     [PA_COMMAND_REQUEST] = pa_command_request,
@@ -90,7 +92,9 @@ static const pa_pdispatch_cb_t command_table[PA_COMMAND_MAX] = {
     [PA_COMMAND_RECORD_STREAM_EVENT] = pa_command_stream_event,
     [PA_COMMAND_CLIENT_EVENT] = pa_command_client_event,
     [PA_COMMAND_PLAYBACK_BUFFER_ATTR_CHANGED] = pa_command_stream_buffer_attr,
-    [PA_COMMAND_RECORD_BUFFER_ATTR_CHANGED] = pa_command_stream_buffer_attr
+    [PA_COMMAND_RECORD_BUFFER_ATTR_CHANGED] = pa_command_stream_buffer_attr,
+    [PA_COMMAND_ENABLE_RINGBUFFER] = pa_command_enable_ringbuffer,
+    [PA_COMMAND_DISABLE_RINGBUFFER] = pa_command_disable_ringbuffer,
 };
 static void context_free(pa_context *c);
 
@@ -1395,6 +1399,58 @@ finish:
     pa_context_unref(c);
 }
 
+static void pa_command_enable_ringbuffer(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata) {
+    pa_context *c = userdata;
+    pa_srchannel *sr;
+    pa_srchannel_template srt;
+    const int *fds;
+    int nfd;
+
+    pa_assert(pd);
+    pa_assert(command == PA_COMMAND_ENABLE_RINGBUFFER);
+    pa_assert(t);
+    pa_assert(c);
+    pa_assert(PA_REFCNT_VALUE(c) >= 1);
+
+    if (!c->srmemblock) {
+        pa_context_fail(c, PA_ERR_PROTOCOL);
+        return;
+    }
+
+    fds = pa_pdispatch_fds(pd, &nfd);
+    if (nfd != 2 || !fds || fds[0] == -1 || fds[1] == -1) {
+        pa_context_fail(c, PA_ERR_PROTOCOL);
+        return;
+    }
+
+    pa_context_ref(c);
+
+    srt.memblock = c->srmemblock;
+    srt.readfd = fds[0];
+    srt.writefd = fds[1];
+    sr = pa_srchannel_new_from_template(c->mainloop, &srt);
+    pa_pstream_send_simple_ack(c->pstream, tag);
+
+    pa_pstream_set_srchannel(c->pstream, sr);
+
+    pa_context_unref(c);
+}
+
+static void pa_command_disable_ringbuffer(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata) {
+    pa_context *c = userdata;
+
+    pa_assert(pd);
+    pa_assert(command == PA_COMMAND_DISABLE_RINGBUFFER);
+    pa_assert(t);
+    pa_assert(c);
+    pa_assert(PA_REFCNT_VALUE(c) >= 1);
+
+    pa_pstream_set_srchannel(c->pstream, NULL);
+
+    pa_pstream_send_simple_ack(c->pstream, tag);
+}
+
+
 void pa_command_client_event(pa_pdispatch *pd, uint32_t command, uint32_t tag, pa_tagstruct *t, void *userdata) {
     pa_context *c = userdata;
     pa_proplist *pl = NULL;
diff --git a/src/pulsecore/native-common.h b/src/pulsecore/native-common.h
index dad82e0..bf94435 100644
--- a/src/pulsecore/native-common.h
+++ b/src/pulsecore/native-common.h
@@ -176,6 +176,10 @@ enum {
     /* Supported since protocol v27 (3.0) */
     PA_COMMAND_SET_PORT_LATENCY_OFFSET,
 
+    /* Supported since protocol v30 (6.0) */
+    PA_COMMAND_ENABLE_RINGBUFFER,
+    PA_COMMAND_DISABLE_RINGBUFFER,
+
     PA_COMMAND_MAX
 };
 
-- 
1.9.1