Handle I2S with Python

pitopd/i2s.py

@@ -0,0 +1,224 @@
+import os
+import re
+import shutil
+import subprocess
+
+# Switch I2S on/off, specifically when targeting pi-topSPEAKER/pi-topPULSE.
+# This is **only** used in conjunction with pi-topHUB v1,
+# as I2S is handled automatically on pi-topHUB v2.
+# To configure for I2S, a custom `asound.conf` file is used to enable mixing
+# multiple audio sources.
+# As well as this, some settings in `/boot/config.txt` are altered:
+#   * `dtoverlay=hifiberry-dac` - enables I2S audio on subsequent boots
+#   * `#dtparam=audio=on` - disables default sound driver
+#   * `dtoverlay=i2s-mmap` - allows multiple audio sources to be mixed together
+#
+# Disabling I2S reverses these changes.
+
+
+TEMP_ASOUND_CONF = "/tmp/asound.conf.tmp"
+BAK_ASOUND_CONF = "/etc/asound.conf.bak"
+ASOUND_CONF = "/etc/asound.conf"
+
+# If we can't access this, there's issues
+with open("/boot/config.txt", "r") as f:
+    contents = f.read()
+
+lines = contents.split("\n")
+
+
+def get_matching_lines(regex):
+    return filter(re.compile(regex).match, lines)
+
+
+def activeOverlayExists(overlay):
+    return len(get_matching_lines(f"^dtoverlay={overlay}$")) > 0
+
+
+def inactiveOverlayExists(overlay):
+    return len(get_matching_lines(f"^#dtoverlay={overlay}$")) > 0
+
+
+def activeParamExists(param):
+    return len(get_matching_lines(f"^dtparam={param}=on$")) > 0
+
+
+def inactiveParamExists(param):
+    return len(get_matching_lines(f"#^dtparam={param}=on$")) > 0
+
+
+def i2sIsEnabledThisSession():
+    return (
+        "rpi_simple_soundcard" in subprocess.run(["lsmod"], capture_output=True).stdout
+    )
+
+
+def i2sIsToBeEnabledNextSession():
+    return (
+        activeOverlayExists("i2s-mmap")
+        and activeOverlayExists("hifiberry-dac")
+        and not activeParamExists("audio")
+    )
+
+
+def setDTOverlayState(overlay, enable):
+    if enable:
+        print(f"Attempting to enable {overlay} overlay...")
+        if activeOverlayExists(overlay):
+            print(f"{overlay} overlay already active - nothing to do")
+        else:
+            print(f"{overlay} overlay not active - enabling")
+            # line = f"dtoverlay={overlay}"
+            if inactiveOverlayExists(overlay):
+                # sudo sed -i "s/^#$line$/$line/1" $CONFIG
+                pass
+            else:
+                # echo "$line" | sudo tee -a $CONFIG &>/dev/null
+                pass
+
+    else:
+        print(f"Attempting to disable {overlay} overlay...")
+        if activeOverlayExists(overlay):
+            print(f"{overlay} overlay active - disabling")
+            # sudo sed -i "s/^$line/#&/1" $CONFIG
+            pass
+        else:
+            print(f"{overlay} overlay not in device tree - nothing to do")
+
+
+def setDTParamState(param, enable):
+    if enable:
+        print(f"Attempting to enable {param} param...")
+        if activeParamExists(param):
+            print(f"{param} param already active - nothing to do")
+        else:
+            print(f"{param} param not active - enabling")
+            # line = f"dtparam={param}=on"
+            if inactiveParamExists(param):
+                # sudo sed -i "s/^#$line$/$line/1" $CONFIG
+                pass
+            else:
+                # echo "$line" | sudo tee -a $CONFIG &>/dev/null
+                pass
+
+    else:
+        print(f"Attempting to disable {param} param...")
+        if activeParamExists(param):
+            print(f"{param} param active - disabling")
+            # sudo sed -i "s/^$line/#&/1" $CONFIG
+            pass
+        else:
+            print(f"{param} param not in device tree - nothing to do")
+
+
+def backupOrigAsoundConf():
+    try:
+        os.remove(BAK_ASOUND_CONF)
+    except OSError:
+        pass
+
+    try:
+        shutil.move(ASOUND_CONF, BAK_ASOUND_CONF)
+    except OSError:
+        pass
+
+
+def restoreOrigAsoundConf():
+    try:
+        os.remove(ASOUND_CONF)
+    except OSError:
+        pass
+
+    try:
+        shutil.move(BAK_ASOUND_CONF, ASOUND_CONF)
+    except OSError:
+        pass
+
+
+def setCustomAsoundConfState(enableCustomConf):
+    if enableCustomConf == 0:
+        backupOrigAsoundConf()
+
+        print("Configuring custom asound.conf")
+
+        with open(TEMP_ASOUND_CONF, "w") as f:
+            f.writelines(
+                [
+                    "pcm.real {",
+                    "  type hw",
+                    "  card 0",
+                    "  device 0",
+                    "}",
+                    "pcm.dmixer {",
+                    "  type dmix",
+                    "  ipc_key 1024",
+                    "  ipc_perm 0666",
+                    '  slave.pcm "real"',
+                    "  slave {",
+                    "    period_time 0",
+                    "    period_size 1024",
+                    "    buffer_size 8192",
+                    "    rate 44100",
+                    "  }",
+                    "  bindings {",
+                    "    0 0",
+                    "    1 1",
+                    "  }",
+                    "}",
+                    "ctl.dmixer {",
+                    "  type hw",
+                    "  card 0",
+                    "}" "pcm.softvol {",
+                    "  type softvol",
+                    '  slave.pcm "dmixer"',
+                    "  control {",
+                    '    name "PCM"',
+                    "    card 0",
+                    "   }",
+                    "}",
+                    "pcm.\041default {",
+                    "   type plug",
+                    '   slave.pcm "softvol"',
+                    "}",
+                ]
+            )
+
+        shutil.move(TEMP_ASOUND_CONF, ASOUND_CONF)
+    else:
+        restoreOrigAsoundConf()
+
+
+def setI2S(command):
+    if command is None or command == "status":
+        desired_i2s_enabled_state = -1
+    elif command == "enable":
+        desired_i2s_enabled_state = 0
+    elif command == "disable":
+        desired_i2s_enabled_state = 1
+    else:
+        return
+
+    if i2sIsEnabledThisSession():
+        print("I2S is currently enabled")
+    else:
+        print("I2S is currently disabled")
+
+    if i2sIsToBeEnabledNextSession:
+        print("I2S is due to be enabled on reboot")
+        if desired_i2s_enabled_state == 0:
+            print("Nothing to do")
+            return
+    else:
+        print("I2S is due to be disabled on reboot")
+        if desired_i2s_enabled_state == 1:
+            print("Nothing to do")
+            return
+
+    if command is None or command == "status":
+        return
+
+    setDTOverlayState("i2s-mmap", desired_i2s_enabled_state)
+    setDTOverlayState("hifiberry-dac", desired_i2s_enabled_state)
+    setDTParamState("audio", 1 - desired_i2s_enabled_state)
+    setDTParamState("i2s", desired_i2s_enabled_state)
+    setCustomAsoundConfState(desired_i2s_enabled_state)