soundwire: slave: lookup SDCA version and functions

Use SDCA helpers to get the basic information and store it in the
slave context. The information will be optionally be used in codec
drivers to register sub-devices for each Function.

When platforms are not based on ACPI the helpers do absolutely
nothing.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

Author: plbossart

drivers/soundwire/Kconfig

@@ -6,6 +6,7 @@
 menuconfig SOUNDWIRE
 	tristate "SoundWire support"
 	depends on ACPI || OF
+	depends on SND_SOC_SDCA_OPTIONAL
 	help
 	  SoundWire is a 2-Pin interface with data and clock line ratified
 	  by the MIPI Alliance. SoundWire is used for transporting data

drivers/soundwire/slave.c

@@ -5,6 +5,7 @@
 #include <linux/of.h>
 #include <linux/soundwire/sdw.h>
 #include <linux/soundwire/sdw_type.h>
+#include <sound/sdca.h>
 #include "bus.h"
 #include "sysfs_local.h"
 
@@ -70,6 +71,17 @@ int sdw_slave_add(struct sdw_bus *bus,
 	list_add_tail(&slave->node, &bus->slaves);
 	mutex_unlock(&bus->bus_lock);
 
+	/*
+	 * The Soundwire driver probe may optionally register SDCA
+	 * sub-devices, one per Function. This means the information
+	 * on the SDCA revision and the number/type of Functions need
+	 * to be extracted from platform firmware before the SoundWire
+	 * driver probe, and as a consequence before the SoundWire
+	 * device_register() below.
+	 */
+	sdca_lookup_interface_revision(slave);
+	sdca_lookup_functions(slave);
+
 	ret = device_register(&slave->dev);
 	if (ret) {
 		dev_err(bus->dev, "Failed to add slave: ret %d\n", ret);
@@ -259,3 +271,5 @@ int sdw_of_find_slaves(struct sdw_bus *bus)
 
 	return 0;
 }
+
+MODULE_IMPORT_NS(SND_SOC_SDCA);