ASoC: SOF: debug: Handle cases when fw_lib_prefix is not set, NULL

The firmware libraries are not supported by IPC3, the fw_lib_path is not
a valid parameter and it is always NULL.
Do not create the debugfs file for IPC3 at all as it is not applicable.

With IPC4 some vendors/platforms might not support loadable libraries and
the fw_lib_prefix is left to NULL to indicate this.
Handle such case with allocating "Not supported" string.
Reviewed-by: Marc Herbert <marc.herbert@intel.com>
Fixes: 17f40412 ("ASoC: SOF: debug: show firmware/topology prefix/names")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20240426153902.39560-2-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/debug.c

@@ -326,8 +326,27 @@ int snd_sof_dbg_init(struct snd_sof_dev *sdev)
 
 	debugfs_create_str("fw_path", 0444, fw_profile,
 			   (char **)&plat_data->fw_filename_prefix);
-	debugfs_create_str("fw_lib_path", 0444, fw_profile,
-			   (char **)&plat_data->fw_lib_prefix);
+	/* library path is not valid for IPC3 */
+	if (plat_data->ipc_type != SOF_IPC_TYPE_3) {
+		/*
+		 * fw_lib_prefix can be NULL if the vendor/platform does not
+		 * support loadable libraries
+		 */
+		if (plat_data->fw_lib_prefix) {
+			debugfs_create_str("fw_lib_path", 0444, fw_profile,
+					   (char **)&plat_data->fw_lib_prefix);
+		} else {
+			static char *fw_lib_path;
+
+			fw_lib_path = devm_kasprintf(sdev->dev, GFP_KERNEL,
+						     "Not supported");
+			if (!fw_lib_path)
+				return -ENOMEM;
+
+			debugfs_create_str("fw_lib_path", 0444, fw_profile,
+					   (char **)&fw_lib_path);
+		}
+	}
 	debugfs_create_str("tplg_path", 0444, fw_profile,
 			   (char **)&plat_data->tplg_filename_prefix);
 	debugfs_create_str("fw_name", 0444, fw_profile,