ASoC: SOF: Add path definition for external firmware libraries

IPC4 based firmware supports dynamically loaded external libraries.
The libraries will be not stored alongside of the firmware or tplg files.

For intel platforms the default path will be:
intel/avs-lib|sof-ipc4-lib/<platform>/ if a community key is used on the
given machine then the libraries will be under 'community' directory, like
it is done for the firmware itself.

Signed-off-by: Peter Ujfalusi <[e-mail]>
Reviewed-by: Ranjani Sridharan <[e-mail]>
Reviewed-by: Pierre-Louis Bossart <[e-mail]>
Reviewed-by: Chao Song <[e-mail]>
Reviewed-by: Kai Vehmanen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

include/sound/sof.h

···
 	const char *tplg_filename_prefix;
 	const char *tplg_filename;
 
+	/* loadable external libraries available under this directory */
+	const char *fw_lib_prefix;
+
 	/* machine */
 	struct platform_device *pdev_mach;
 	const struct snd_soc_acpi_mach *machine;
···
 	unsigned int ipc_supported_mask;
 	enum sof_ipc_type ipc_default;
 
-	/* defaults paths for firmware and topology files */
+	/* defaults paths for firmware, library and topology files */
 	const char *default_fw_path[SOF_IPC_TYPE_COUNT];
+	const char *default_lib_path[SOF_IPC_TYPE_COUNT];
 	const char *default_tplg_path[SOF_IPC_TYPE_COUNT];
 
 	/* default firmware name */

sound/soc/sof/intel/pci-tgl.c

···
 		[SOF_IPC] = "intel/sof",
 		[SOF_INTEL_IPC4] = "intel/avs/adl-n",
 	},
+	.default_lib_path = {
+		[SOF_INTEL_IPC4] = "intel/avs-lib/adl-n",
+	},
 	.default_tplg_path = {
 		[SOF_IPC] = "intel/sof-tplg",
 		[SOF_INTEL_IPC4] = "intel/avs-tplg",

sound/soc/sof/sof-pci-dev.c

···
 module_param(fw_filename, charp, 0444);
 MODULE_PARM_DESC(fw_filename, "alternate filename for SOF firmware.");
 
+static char *lib_path;
+module_param(lib_path, charp, 0444);
+MODULE_PARM_DESC(lib_path, "alternate path for SOF firmware libraries.");
+
 static char *tplg_path;
 module_param(tplg_path, charp, 0444);
 MODULE_PARM_DESC(tplg_path, "alternate path for SOF topology.");
···
 	} else {
 		sof_pdata->fw_filename_prefix =
 			sof_pdata->desc->default_fw_path[sof_pdata->ipc_type];
+	}
+
+	if (lib_path) {
+		sof_pdata->fw_lib_prefix = lib_path;
+
+		dev_dbg(dev, "Module parameter used, changed fw_lib path to %s\n",
+			sof_pdata->fw_lib_prefix);
+
+	} else if (sof_pdata->desc->default_lib_path[sof_pdata->ipc_type]) {
+		if (dmi_check_system(community_key_platforms) && sof_dmi_use_community_key) {
+			sof_pdata->fw_lib_prefix =
+				devm_kasprintf(dev, GFP_KERNEL, "%s/%s",
+					sof_pdata->desc->default_lib_path[sof_pdata->ipc_type],
+					"community");
+
+			dev_dbg(dev,
+				"Platform uses community key, changed fw_lib path to %s\n",
+				sof_pdata->fw_lib_prefix);
+		} else {
+			sof_pdata->fw_lib_prefix =
+				sof_pdata->desc->default_lib_path[sof_pdata->ipc_type];
+		}
 	}
 
 	if (tplg_path)