ASoC: SDCA: add function devices

Use the auxiliary bus to register/unregister subdevices for each
function. Each function will be handled with a separate driver,
matched using a name.

If a vendor wants to override a specific function driver, they could
use a custom name to match with a custom function driver.

Signed-off-by: Pierre-Louis Bossart <[e-mail]>
Tested-by: Bard Liao <[e-mail]>
Reviewed-by: Maciej Strozek <[e-mail]>
Reviewed-by: Peter Ujfalusi <[e-mail]>
Tested-by: Richard Fitzgerald <[e-mail]>
Signed-off-by: Charles Keepax <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Reviewed-by: Vinod Koul <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

include/sound/sdca.h

···
 struct acpi_table_swft;
 struct fwnode_handle;
 struct sdw_slave;
+struct sdca_dev;
 
 #define SDCA_MAX_FUNCTION_COUNT 8
 
 /**
  * struct sdca_function_desc - short descriptor for an SDCA Function
  * @node: firmware node for the Function.
+ * @func_dev: pointer to SDCA function device.
  * @name: Human-readable string.
  * @type: Function topology type.
  * @adr: ACPI address (used for SDCA register access).
  */
 struct sdca_function_desc {
 	struct fwnode_handle *node;
+	struct sdca_dev *func_dev;
 	const char *name;
 	u32 type;
 	u8 adr;
···
 void sdca_lookup_swft(struct sdw_slave *slave);
 void sdca_lookup_interface_revision(struct sdw_slave *slave);
 bool sdca_device_quirk_match(struct sdw_slave *slave, enum sdca_quirk quirk);
+int sdca_dev_register_functions(struct sdw_slave *slave);
+void sdca_dev_unregister_functions(struct sdw_slave *slave);
 
 #else
 
···
 {
 	return false;
 }
+
+static inline int sdca_dev_register_functions(struct sdw_slave *slave)
+{
+	return 0;
+}
+
+static inline void sdca_dev_unregister_functions(struct sdw_slave *slave) {}
+
 #endif
 
 #endif

sound/soc/sdca/Kconfig

···
 config SND_SOC_SDCA
 	tristate
 	depends on ACPI
+	select AUXILIARY_BUS
 	help
 	  This option enables support for the MIPI SoundWire Device
 	  Class for Audio (SDCA).

sound/soc/sdca/Makefile

···
 # SPDX-License-Identifier: GPL-2.0-only
 
-snd-soc-sdca-y := sdca_functions.o sdca_device.o sdca_regmap.o sdca_asoc.o \
-		  sdca_ump.o
+snd-soc-sdca-y := sdca_functions.o sdca_device.o sdca_function_device.o \
+		  sdca_regmap.o sdca_asoc.o sdca_ump.o
 snd-soc-sdca-$(CONFIG_SND_SOC_SDCA_HID) += sdca_hid.o
 snd-soc-sdca-$(CONFIG_SND_SOC_SDCA_IRQ) += sdca_interrupts.o
 snd-soc-sdca-$(CONFIG_SND_SOC_SDCA_FDL) += sdca_fdl.o

sound/soc/sdca/sdca_function_device.c

···
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+// Copyright(c) 2024 Intel Corporation.
+
+/*
+ * SDCA Function Device management
+ */
+
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/auxiliary_bus.h>
+#include <linux/soundwire/sdw.h>
+#include <sound/sdca.h>
+#include <sound/sdca_function.h>
+#include "sdca_function_device.h"
+
+/*
+ * A SoundWire device can have multiple SDCA functions identified by
+ * their type and ADR. there can be multiple SoundWire devices per
+ * link, or multiple devices spread across multiple links. An IDA is
+ * required to identify each instance.
+ */
+static DEFINE_IDA(sdca_function_ida);
+
+static void sdca_dev_release(struct device *dev)
+{
+	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
+	struct sdca_dev *sdev = auxiliary_dev_to_sdca_dev(auxdev);
+
+	ida_free(&sdca_function_ida, auxdev->id);
+	kfree(sdev);
+}
+
+/* alloc, init and add link devices */
+static struct sdca_dev *sdca_dev_register(struct device *parent,
+					  struct sdca_function_desc *function_desc)
+{
+	struct sdca_dev *sdev;
+	struct auxiliary_device *auxdev;
+	int ret;
+	int rc;
+
+	sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
+	if (!sdev)
+		return ERR_PTR(-ENOMEM);
+
+	auxdev = &sdev->auxdev;
+	auxdev->name = function_desc->name;
+	auxdev->dev.parent = parent;
+	auxdev->dev.fwnode = function_desc->node;
+	auxdev->dev.release = sdca_dev_release;
+
+	sdev->function.desc = function_desc;
+
+	rc = ida_alloc(&sdca_function_ida, GFP_KERNEL);
+	if (rc < 0) {
+		kfree(sdev);
+		return ERR_PTR(rc);
+	}
+	auxdev->id = rc;
+
+	/* now follow the two-step init/add sequence */
+	ret = auxiliary_device_init(auxdev);
+	if (ret < 0) {
+		dev_err(parent, "failed to initialize SDCA function dev %s\n",
+			function_desc->name);
+		ida_free(&sdca_function_ida, auxdev->id);
+		kfree(sdev);
+		return ERR_PTR(ret);
+	}
+
+	ret = auxiliary_device_add(auxdev);
+	if (ret < 0) {
+		dev_err(parent, "failed to add SDCA function dev %s\n",
+			sdev->auxdev.name);
+		/* sdev will be freed with the put_device() and .release sequence */
+		auxiliary_device_uninit(&sdev->auxdev);
+		return ERR_PTR(ret);
+	}
+
+	return sdev;
+}
+
+static void sdca_dev_unregister(struct sdca_dev *sdev)
+{
+	auxiliary_device_delete(&sdev->auxdev);
+	auxiliary_device_uninit(&sdev->auxdev);
+}
+
+int sdca_dev_register_functions(struct sdw_slave *slave)
+{
+	struct sdca_device_data *sdca_data = &slave->sdca_data;
+	int i;
+
+	for (i = 0; i < sdca_data->num_functions; i++) {
+		struct sdca_dev *func_dev;
+
+		func_dev = sdca_dev_register(&slave->dev,
+					     &sdca_data->function[i]);
+		if (!func_dev)
+			return -ENODEV;
+
+		sdca_data->function[i].func_dev = func_dev;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_NS(sdca_dev_register_functions, "SND_SOC_SDCA");
+
+void sdca_dev_unregister_functions(struct sdw_slave *slave)
+{
+	struct sdca_device_data *sdca_data = &slave->sdca_data;
+	int i;
+
+	for (i = 0; i < sdca_data->num_functions; i++)
+		sdca_dev_unregister(sdca_data->function[i].func_dev);
+}
+EXPORT_SYMBOL_NS(sdca_dev_unregister_functions, "SND_SOC_SDCA");

sound/soc/sdca/sdca_function_device.h

···
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
+/* Copyright(c) 2024 Intel Corporation. */
+
+#ifndef __SDCA_FUNCTION_DEVICE_H
+#define __SDCA_FUNCTION_DEVICE_H
+
+struct sdca_dev {
+	struct auxiliary_device auxdev;
+	struct sdca_function_data function;
+};
+
+#define auxiliary_dev_to_sdca_dev(auxiliary_dev)		\
+	container_of(auxiliary_dev, struct sdca_dev, auxdev)
+
+#endif