Switch to PortAudio

Switch to PortAudio for cross-platform and cross backend compatibility.

Linux v6.7 propose a solution to resolve sound stutter effect.
Therefore, upgrade the kernel version as well.

It is confirmed that there exists unknown issues in Linux Kernel
that user has to adjust the buffer size to more than four times of period size,
or the program cannot write PCM frames into guest ALSA stack.

Author: Cuda-Chen

.clang-format

@@ -24,3 +24,5 @@ ForEachMacros:
   - hlist_for_each_entry
   - rb_list_foreach
   - rb_list_foreach_safe
+StatementAttributeLikeMacros:
+  - IIF

.gitmodules

@@ -1,12 +1,12 @@
-[submodule "cnfa"]
-    path = cnfa
-    url = https://github.com/cntools/cnfa
-    shallow = true
 [submodule "mini-gdbstub"]
     path = mini-gdbstub
     url = https://github.com/RinHizakura/mini-gdbstub
     shallow = true
 [submodule "minislirp"]
 	path = minislirp
 	url = https://github.com/edubart/minislirp
-    shallow = true
+    shallow = true
+[submodule "portaudio"]
+    path = portaudio
+    url = https://github.com/PortAudio/portaudio
+    shallow = true

Makefile

@@ -14,7 +14,7 @@ OBJS_EXTRA :=
 # command line option
 OPTS :=
 
-LDFLAGS := -lm
+LDFLAGS :=
 
 # virtio-blk
 ENABLE_VIRTIOBLK ?= 1
@@ -56,37 +56,61 @@ endif
 
 # virtio-snd
 ENABLE_VIRTIOSND ?= 1
-ifneq ($(UNAME_S),$(filter $(UNAME_S),Linux))
+ifneq ($(UNAME_S),$(filter $(UNAME_S),Linux Darwin))
     ENABLE_VIRTIOSND := 0
 endif
 
-# Check ALSA installation
 ifeq ($(UNAME_S),Linux)
+    # Check ALSA installation
     ifeq (0, $(call check-alsa))
         $(warning No libasound installed. Check libasound in advance.)
         ENABLE_VIRTIOSND := 0
     endif
 endif
+ifeq ($(UNAME_S),Darwin)
+    ifeq (0, $(call check-coreaudio))
+        $(warning No CoreAudio installed Check AudioToolbox in advance.)
+        ENABLE_VIRTIOSND := 0
+    endif
+endif
 $(call set-feature, VIRTIOSND)
 ifeq ($(call has, VIRTIOSND), 1)
     OBJS_EXTRA += virtio-snd.o
 
-    LDFLAGS += -lasound -lpthread
-    CFLAGS += -Icnfa
+    PORTAUDIOLIB := portaudio/lib/.libs/libportaudio.a
+    LDFLAGS += $(PORTAUDIOLIB)
 
-cnfa/Makefile:
-	git submodule update --init cnfa
-cnfa/os_generic: cnfa/Makefile
-	$(MAKE) -C $(dir $<) os_generic.h
-CNFA_LIB := cnfa/CNFA_sf.h
-$(CNFA_LIB): cnfa/Makefile cnfa/os_generic
-	$(MAKE) -C $(dir $<) CNFA_sf.h
-main.o: $(CNFA_LIB)
+    ifeq ($(UNAME_S),Linux)
+        LDFLAGS += -lasound -lrt
+        # Check PulseAudio installation
+        ifeq (0, $(call check-pa))
+            LDFLAGS += -lpulse
+        endif
+    endif
+    ifeq ($(UNAME_S),Darwin)
+        LDFLAGS += -framework CoreServices -framework CoreFoundation -framework AudioUnit -framework AudioToolbox -framework CoreAudio
+    endif
 
-# suppress warning when compiling CNFA
-virtio-snd.o: CFLAGS += -Wno-unused-parameter -Wno-sign-compare
+    CFLAGS += -Iportaudio/include
+    # PortAudio requires libm, yet we set -lm in the end of LDFLAGS
+    # so that the other libraries will be benefited for no need to set
+    # -lm separately.
+    LDFLAGS += -lpthread
+
+portaudio/Makefile:
+	git submodule update --init portaudio
+$(PORTAUDIOLIB): portaudio/Makefile
+	cd $(dir $<) && ./configure
+	$(MAKE) -C $(dir $<)
+main.o: $(PORTAUDIOLIB)
+
+# suppress warning when compiling PortAudio
+virtio-snd.o: CFLAGS += -Wno-unused-parameter
 endif
 
+# Set libm as the last dependency so that no need to set -lm seperately.
+LDFLAGS += -lm
+
 # .DEFAULT_GOAL should be set to all since the very first target is not all
 # after git submodule.
 .DEFAULT_GOAL := all

README.md

@@ -12,9 +12,12 @@ A minimalist RISC-V system emulator capable of running Linux the kernel and corr
 - Three types of I/O support using VirtIO standard:
     - virtio-blk acquires disk image from the host.
     - virtio-net is mapped as TAP interface.
-    - virtio-snd uses ALSA for sound operation with the following limitations:
-        - The emulator will hang if PulseAudio is enabled on host.
-        - The playback may plays with repeating artifact.
+    - virtio-snd uses [PortAudio](https://github.com/PortAudio/portaudio) for sound playback on the host with one limitations:
+        - As some unknown issues in guest Linux OS (confirmed in v6.7 and v6.12), you need
+          to adjust the buffer size to more than four times of period size, or
+          the program cannot write the PCM frames into guest OS ALSA stack.
+            - For instance, the following buffer/period size settings on `aplay` has been tested
+              with broken and stutter effects yet complete with no any errors: `aplay --buffer-size=32768 --period-size=4096 /usr/share/sounds/alsa/Front_Center.wav`.
 
 ## Prerequisites
 

cnfa

@@ -34,3 +34,19 @@ static inline int ilog2(int x)
 #else /* unsupported compilers */
 #define PACKED(name)
 #endif
+
+/* Pattern Matching for C macros.
+ * https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
+ */
+
+/* In Visual Studio, __VA_ARGS__ is treated as a separate parameter. */
+#define FIX_VC_BUG(x) x
+
+/* catenate */
+#define PRIMITIVE_CAT(a, ...) FIX_VC_BUG(a##__VA_ARGS__)
+
+#define IIF(c) PRIMITIVE_CAT(IIF_, c)
+/* run the 2nd parameter */
+#define IIF_0(t, ...) __VA_ARGS__
+/* run the 1st parameter */
+#define IIF_1(t, ...) t

common.h

@@ -945,6 +945,7 @@ CONFIG_DUMMY_CONSOLE_ROWS=25
 CONFIG_SOUND=y
 CONFIG_SND=y
 CONFIG_SND_VIRTIO=y
+CONFIG_SND_HRTIMER=y
 
 #
 # HID support

configs/linux.config

@@ -10,8 +10,41 @@ int main(){\n\
 }\n'
 endef
 
+# Create a mininal PulseAudio program
+define create-pa-prog
+echo '\
+#include <pulse/mainloop.h>\n\
+int main(){\n\
+    pa_mainloop *m;\n\
+    return 0;\n\
+}\n'
+endef
+
+# Create a mininal CoreAudio program
+define create-ca-prog
+echo '\
+#include <CoreAudio/CoreAudio.h>\n\
+#include <AudioToolbox/AudioQueue.h>
+int main(){\n\
+    AudioQueueRef queue;\n\
+    AudioQueueDispose(queue, TRUE);\n\
+    return 0;\n\
+}\n'
+endef
+
 # Check ALSA installation
 define check-alsa
 $(shell $(call create-alsa-prog) | $(CC) -x c -lasound -o /dev/null > /dev/null 2> /dev/null - 
 	&& echo $$?)
 endef
+
+# Check PulseAudio installation
+define check-pa
+$(shell $(call create-pa-prog) | $(CC) -x c -lpulse -o /dev/null - && echo 0 || echo 1)
+endef
+
+# Check CoreAudio installation
+define check-coreaudio
+$(shell $(call create-ca-prog) | $(CC) -x c -framework AudioToolbox -o /dev/null > /dev/null 2> /dev/null - 
+	&& echo $$?)
+endef