SDL audio support

This patch implements a Genode-specific audio backend for SDL.

The audio volume (in percent) can be configured in the config file of the
SDL application:

<config>
	<sdl_audio_volume value="100"/>
</config>

Fixes #204.

libports/lib/mk/sdl.mk

@@ -93,7 +93,8 @@ SRC_C   += SDL_audio.c \
            SDL_mixer_MMX.c \
            SDL_mixer_MMX_VC.c \
            SDL_wave.c \
-           SDL_dummyaudio.c
+           SDL_genodeaudio.c
+INC_DIR += $(SDL_DIR)/src/audio
 
 # file I/O subsystem
 SRC_C   += SDL_rwops.c
@@ -114,6 +115,7 @@ CC_OPT_SDL_wave     += -Wno-unused-but-set-variable
 
 # backend pathes
 vpath %    $(REP_DIR)/src/lib/sdl
+vpath %    $(REP_DIR)/src/lib/sdl/audio
 vpath %    $(REP_DIR)/src/lib/sdl/video
 
 # contribution pathes
@@ -125,7 +127,6 @@ vpath %.c  $(SDL_DIR)/src/stdlib
 vpath %.c  $(SDL_DIR)/src/video
 vpath %.c  $(SDL_DIR)/src/video/dummy
 vpath %.c  $(SDL_DIR)/src/audio
-vpath %.c  $(SDL_DIR)/src/audio/dummy
 vpath %.c  $(SDL_DIR)/src/thread
 vpath %.c  $(SDL_DIR)/src/thread/pthread
 vpath %.c  $(SDL_DIR)/src/timer

libports/ports/sdl.mk

@@ -25,6 +25,7 @@ $(CONTRIB_DIR)/$(SDL): $(DOWNLOAD_DIR)/$(SDL_TGZ)
 	$(VERBOSE)tar xfz $< -C $(CONTRIB_DIR) && touch $@
 	$(VERBOSE)rm -f $@/include/SDL_config.h
 	$(VERBOSE)patch -p0 -i src/lib/sdl/SDL_video.patch
+	$(VERBOSE)patch -d $(CONTRIB_DIR)/$(SDL) -p1 -i ../../src/lib/sdl/SDL_audio.patch
 
 #
 # Install SDL headers

libports/src/lib/sdl/SDL_audio.patch

@@ -0,0 +1,26 @@
+diff --git a/src/audio/SDL_audio.c b/src/audio/SDL_audio.c
+--- a/src/audio/SDL_audio.c
++++ b/src/audio/SDL_audio.c
+@@ -113,6 +113,9 @@
+ #if SDL_AUDIO_DRIVER_EPOCAUDIO
+ 	&EPOCAudio_bootstrap,
+ #endif
++#if SDL_AUDIO_DRIVER_GENODE
++	&GENODEAUD_bootstrap,
++#endif
+ 	NULL
+ };
+ SDL_AudioDevice *current_audio = NULL;
+diff --git a/src/audio/SDL_sysaudio.h b/src/audio/SDL_sysaudio.h
+--- a/src/audio/SDL_sysaudio.h
++++ b/src/audio/SDL_sysaudio.h
+@@ -177,6 +177,9 @@
+ #if SDL_AUDIO_DRIVER_EPOCAUDIO
+ extern AudioBootStrap EPOCAudio_bootstrap; 
+ #endif
++#if SDL_AUDIO_DRIVER_GENODE
++extern AudioBootStrap GENODEAUD_bootstrap;
++#endif
+ 
+ /* This is the current audio device */
+ extern SDL_AudioDevice *current_audio;

libports/src/lib/sdl/SDL_config_genode.h

@@ -38,8 +38,8 @@
 #include <stdio.h>
 #include <sys/types.h>
 
-/* Enable the dummy audio driver (src/audio/dummy/\*.c) */
-#define SDL_AUDIO_DRIVER_DUMMY 1
+/* Enable the Genode audio driver */
+#define SDL_AUDIO_DRIVER_GENODE 1
 
 /* Enable the stub cdrom driver (src/cdrom/dummy/\*.c) */
 #define SDL_CDROM_DISABLED 1

libports/src/lib/sdl/audio/SDL_genodeaudio.cc

@@ -0,0 +1,264 @@
+/*
+ * \brief  Genode-specific audio backend
+ * \author Christian Prochaska
+ * \date   2012-03-13
+ *
+ * based on the dummy SDL audio driver
+ */
+
+/*
+ * Copyright (C) 2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#include <base/allocator_avl.h>
+#include <base/printf.h>
+#include <base/thread.h>
+#include <audio_out_session/connection.h>
+#include <os/config.h>
+
+enum {
+	AUDIO_OUT_SAMPLE_SIZE = sizeof(float),
+	AUDIO_OUT_CHANNELS = 2,
+	AUDIO_OUT_FREQ = 44100,
+	AUDIO_OUT_SAMPLES = 1024,
+};
+
+using Genode::env;
+using Genode::Allocator_avl;
+using Genode::Signal_context;
+using Genode::Signal_receiver;
+
+static const char *channel_names[] = { "front left", "front right" };
+static float volume = 1.0;
+static Signal_context config_signal_context;
+
+extern "C" {
+
+#include "SDL_config.h"
+
+/* Output audio to Genode audio service. */
+
+#include "SDL_rwops.h"
+#include "SDL_timer.h"
+#include "SDL_audio.h"
+#include "SDL_audiomem.h"
+#include "SDL_audio_c.h"
+#include "SDL_audiodev_c.h"
+#include "SDL_genodeaudio.h"
+
+/* The tag name used by Genode audio */
+#define GENODEAUD_DRIVER_NAME "genode"
+
+typedef Audio_out::Session::Channel::Source Stream;
+
+
+struct SDL_PrivateAudioData {
+	Uint8 *mixbuf;
+	Uint32 mixlen;
+	Genode::Allocator_avl *block_alloc[AUDIO_OUT_CHANNELS];
+	Audio_out::Connection *audio_out[AUDIO_OUT_CHANNELS];
+	Stream *stream[AUDIO_OUT_CHANNELS];
+};
+
+
+/*
+ * The first 'Signal_receiver' object in a process creates a signal receiver
+ * thread. Currently this must not happen before the main program has started
+ * or else the thread's context area would get overmapped on Genode/Linux when
+ * the main program calls 'main_thread_bootstrap()' from '_main()'.
+ */
+static Signal_receiver *signal_receiver()
+{
+	static Signal_receiver _signal_receiver;
+	return &_signal_receiver;
+}
+
+
+static void read_config()
+{
+	/* read volume from config file */
+	try {
+		unsigned int config_volume;
+		Genode::config()->xml_node().sub_node("sdl_audio_volume").attribute("value").value(&config_volume);
+		volume = (float)config_volume / 100;
+	}
+	catch (Genode::Config::Invalid) { }
+	catch (Genode::Xml_node::Nonexistent_sub_node) { }
+	catch (Genode::Xml_node::Nonexistent_attribute) { }
+}
+
+
+/* Audio driver functions */
+static int GENODEAUD_OpenAudio(_THIS, SDL_AudioSpec *spec);
+static void GENODEAUD_WaitAudio(_THIS);
+static void GENODEAUD_PlayAudio(_THIS);
+static Uint8 *GENODEAUD_GetAudioBuf(_THIS);
+static void GENODEAUD_CloseAudio(_THIS);
+
+
+/* Audio driver bootstrap functions */
+static int GENODEAUD_Available(void)
+{
+	return 1;
+}
+
+
+static void GENODEAUD_DeleteDevice(SDL_AudioDevice *device)
+{
+	for (int channel = 0; channel < AUDIO_OUT_CHANNELS; channel++) {
+		destroy(env()->heap(), device->hidden->audio_out[channel]);
+		destroy(env()->heap(), device->hidden->block_alloc[channel]);
+	}
+
+	SDL_free(device->hidden);
+	SDL_free(device);
+}
+
+
+static SDL_AudioDevice *GENODEAUD_CreateDevice(int devindex)
+{
+	SDL_AudioDevice *_this;
+
+	/* Initialize all variables that we clean on shutdown */
+	_this = (SDL_AudioDevice *)SDL_malloc(sizeof(SDL_AudioDevice));
+	if ( _this ) {
+		SDL_memset(_this, 0, (sizeof *_this));
+		_this->hidden = (struct SDL_PrivateAudioData *)
+				SDL_malloc((sizeof *_this->hidden));
+	}
+	if ( (_this == NULL) || (_this->hidden == NULL) ) {
+		SDL_OutOfMemory();
+		if ( _this ) {
+			SDL_free(_this);
+		}
+		return(0);
+	}
+	SDL_memset(_this->hidden, 0, (sizeof *_this->hidden));
+
+	/* Set the function pointers */
+	_this->OpenAudio = GENODEAUD_OpenAudio;
+	_this->WaitAudio = GENODEAUD_WaitAudio;
+	_this->PlayAudio = GENODEAUD_PlayAudio;
+	_this->GetAudioBuf = GENODEAUD_GetAudioBuf;
+	_this->CloseAudio = GENODEAUD_CloseAudio;
+
+	_this->free = GENODEAUD_DeleteDevice;
+
+	/* connect to 'Audio_out' service */
+	for (int channel = 0; channel < AUDIO_OUT_CHANNELS; channel++) {
+		_this->hidden->block_alloc[channel] = new (env()->heap()) Allocator_avl(env()->heap());
+		try {
+			_this->hidden->audio_out[channel] = new (env()->heap())
+				Audio_out::Connection(channel_names[channel], _this->hidden->block_alloc[channel]);
+			_this->hidden->stream[channel] = _this->hidden->audio_out[channel]->stream();
+		} catch(Genode::Parent::Service_denied) {
+			PERR("Could not connect to 'Audio_out' service.");
+			destroy(env()->heap(), _this->hidden->block_alloc[channel]);
+			while(--channel > 0) {
+				destroy(env()->heap(), _this->hidden->audio_out[channel]);
+				destroy(env()->heap(), _this->hidden->block_alloc[channel]);
+			}
+			return NULL;
+		}
+		if (channel > 0)
+			_this->hidden->audio_out[channel]->sync_session(_this->hidden->audio_out[channel-1]->session_capability());
+	}
+
+	Genode::config()->sigh(signal_receiver()->manage(&config_signal_context));
+	read_config();
+
+	return _this;
+}
+
+
+AudioBootStrap GENODEAUD_bootstrap = {
+	GENODEAUD_DRIVER_NAME, "Genode audio driver",
+	GENODEAUD_Available, GENODEAUD_CreateDevice
+};
+
+
+/* This function waits until it is possible to write a full sound buffer */
+static void GENODEAUD_WaitAudio(_THIS)
+{
+	for (int channel = 0; channel < AUDIO_OUT_CHANNELS; channel++)
+		while (_this->hidden->stream[channel]->ack_avail() ||
+		       !_this->hidden->stream[channel]->ready_to_submit()) {
+			_this->hidden->stream[channel]->release_packet(_this->hidden->stream[channel]->get_acked_packet());
+		}
+}
+
+
+static void GENODEAUD_PlayAudio(_THIS)
+{
+	Packet_descriptor p[AUDIO_OUT_CHANNELS];
+
+	for (int channel = 0; channel < AUDIO_OUT_CHANNELS; channel++)
+		while (1)
+			try {
+				p[channel] = _this->hidden->stream[channel]->alloc_packet(AUDIO_OUT_SAMPLE_SIZE * AUDIO_OUT_SAMPLES);
+				break;
+			} catch (Stream::Packet_alloc_failed) {
+				/* wait for next finished packet */
+				_this->hidden->stream[channel]->release_packet(_this->hidden->stream[channel]->get_acked_packet());
+			}
+
+	if (signal_receiver()->pending()) {
+		signal_receiver()->wait_for_signal();
+		Genode::config()->reload();
+		read_config();
+	}
+
+	for (int sample = 0; sample < AUDIO_OUT_SAMPLES; sample++)
+		for (int channel = 0; channel < AUDIO_OUT_CHANNELS; channel++)
+			_this->hidden->stream[channel]->packet_content(p[channel])[sample] =
+				volume * (float)(((int16_t*)_this->hidden->mixbuf)[sample * AUDIO_OUT_CHANNELS + channel]) / 32768;
+
+	for (int channel = 0; channel < AUDIO_OUT_CHANNELS; channel++)
+		_this->hidden->stream[channel]->submit_packet(p[channel]);
+}
+
+
+static Uint8 *GENODEAUD_GetAudioBuf(_THIS)
+{
+	return(_this->hidden->mixbuf);
+}
+
+
+static void GENODEAUD_CloseAudio(_THIS)
+{
+	if ( _this->hidden->mixbuf != NULL ) {
+		SDL_FreeAudioMem(_this->hidden->mixbuf);
+		_this->hidden->mixbuf = NULL;
+	}
+}
+
+
+static int GENODEAUD_OpenAudio(_THIS, SDL_AudioSpec *spec)
+{
+	PDBG("requested freq = %d", spec->freq);
+	PDBG("requested format = 0x%x", spec->format);
+	PDBG("requested samples = %u", spec->samples);
+	PDBG("requested size = %u", spec->size);
+
+	spec->channels = AUDIO_OUT_CHANNELS;
+	spec->format = AUDIO_S16LSB;
+	spec->freq = AUDIO_OUT_FREQ;
+	spec->samples = AUDIO_OUT_SAMPLES;
+	SDL_CalculateAudioSpec(spec);
+
+	/* Allocate mixing buffer */
+	_this->hidden->mixlen = spec->size;
+	_this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(_this->hidden->mixlen);
+	if ( _this->hidden->mixbuf == NULL ) {
+		return(-1);
+	}
+	SDL_memset(_this->hidden->mixbuf, spec->silence, spec->size);
+
+	/* We're ready to rock and roll. :-) */
+	return(0);
+}
+
+}

libports/src/lib/sdl/audio/SDL_genodeaudio.h

@@ -0,0 +1,26 @@
+/*
+ * \brief  Genode-specific audio backend
+ * \author Christian Prochaska
+ * \date   2012-03-13
+ *
+ * based on the dummy SDL audio driver
+ */
+
+/*
+ * Copyright (C) 2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#include "SDL_config.h"
+
+#ifndef _SDL_genodeaudio_h
+#define _SDL_genodeaudio_h
+
+#include "SDL_sysaudio.h"
+
+/* Hidden "this" pointer for the video functions */
+#define _THIS	SDL_AudioDevice *_this
+
+#endif /* _SDL_genodeaudio_h */