case-lib: is_ipc4: use new debugfs file instead of kernel parameter

First step to remove use of kernel parameters

Link: thesofproject/linux#4902
Link: #1166

Signed-off-by: Pierre-Louis Bossart <[email protected]>

case-lib/lib.sh

@@ -813,22 +813,47 @@ is_firmware_file_zephyr()
 is_ipc4()
 {
     local ipc_type
-    ipc_file=/sys/module/snd_sof_pci/parameters/ipc_type
 
-    # If /sys/module/snd_sof_pci/parameters/ipc_type does not exist
-    # the DUT is running IPC3 mode
-    ipc_type=$(cat $ipc_file) || {
-        return 1
-    }
+    if ipc_type=$(cat /sys/kernel/debug/sof/ipc_type); then
+	# "cat" was successful
+	case $ipc_type in
+	    0)
+		return 1
+		;;
+	    1)
+		return 0 # in shell, success = error code 0 = "true"
+		;;
+	    *)
+		die "invalid ipc_type in /sys/kernel/debug/sof/ipc_type=$ipc_type"
+		;;
+	esac
+    fi
 
-    # If /sys/module/snd_sof_pci/parameters/ipc_type exists
-    # If the value of file ipc_type is:
-    # -1: DUT runs IPC3 mode, is_ipc4 return 1(false)
-    # 1: DUT runs IPC4 mode, is_ipc4 return 0(true)
-    if [ "$ipc_type" -eq 1 ]; then
-        return 0
+    # "cat" failed, backwards-compatible fallback with ipc_type kernel parameter
+    if ipc_type=$(cat /sys/module/snd_sof_pci/parameters/ipc_type); then
+	# "cat" was successful
+	case $ipc_type in
+	    -1)
+		# the parameter is not set, assume IPC3 was used.
+		return 1
+		;;
+	    0)
+		# the parameter is set, IPC3 was used.
+		return 1
+		;;
+	    1)
+		# the parameter is set, IPC4 was used.
+		return 0 # in shell, success = error code 0 = "true"
+		;;
+	    *)
+		die "invalid ipc_type in /sys/module/snd_sof_pci/parameters/ipc_type=$ipc_type"
+		;;
+	esac
     fi
-    return 1
+
+    # If /sys/module/snd_sof_pci/parameters/ipc_type does not exist
+    #  assume IPC3 was used.
+   return 1
 }
 
 logger_disabled()