soundwire: bus_type: add sdw_master_device support

In the existing SoundWire code, Master Devices are not explicitly
represented - only SoundWire Slave Devices are exposed (the use of
capital letters follows the SoundWire specification conventions).

With the existing code, the bus is handled without using a proper device,
and bus->dev typically points to a platform device. The right thing to
do as discussed in multiple reviews is use a device for each bus.

The sdw_master_device addition is done with minimal internal plumbing
and not exposed externally. The existing API based on
sdw_bus_master_add() and sdw_bus_master_delete() will deal with the
sdw_master_device life cycle, which minimizes changes to existing
drivers.

Note that the Intel code will be modified in follow-up patches (no
impact on any platform since the connection with ASoC is not supported
upstream so far).

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Acked-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20200518174322.31561-5-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 81 insertions, 0 deletions

diff --git a/drivers/soundwire/master.c b/drivers/soundwire/master.c
new file mode 100644
index 000000000000..6be0a027def7
--- /dev/null
+++ b/drivers/soundwire/master.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright(c) 2019-2020 Intel Corporation.
+
+#include <linux/device.h>
+#include <linux/acpi.h>
+#include <linux/soundwire/sdw.h>
+#include <linux/soundwire/sdw_type.h>
+#include "bus.h"
+
+static void sdw_master_device_release(struct device *dev)
+{
+	struct sdw_master_device *md = dev_to_sdw_master_device(dev);
+
+	kfree(md);
+}
+
+struct device_type sdw_master_type = {
+	.name =		"soundwire_master",
+	.release =	sdw_master_device_release,
+};
+
+/**
+ * sdw_master_device_add() - create a Linux Master Device representation.
+ * @bus: SDW bus instance
+ * @parent: parent device
+ * @fwnode: firmware node handle
+ */
+int sdw_master_device_add(struct sdw_bus *bus, struct device *parent,
+			  struct fwnode_handle *fwnode)
+{
+	struct sdw_master_device *md;
+	int ret;
+
+	if (!parent)
+		return -EINVAL;
+
+	md = kzalloc(sizeof(*md), GFP_KERNEL);
+	if (!md)
+		return -ENOMEM;
+
+	md->dev.bus = &sdw_bus_type;
+	md->dev.type = &sdw_master_type;
+	md->dev.parent = parent;
+	md->dev.of_node = parent->of_node;
+	md->dev.fwnode = fwnode;
+	md->dev.dma_mask = parent->dma_mask;
+
+	dev_set_name(&md->dev, "sdw-master-%d", bus->id);
+
+	ret = device_register(&md->dev);
+	if (ret) {
+		dev_err(parent, "Failed to add master: ret %d\n", ret);
+		/*
+		 * On err, don't free but drop ref as this will be freed
+		 * when release method is invoked.
+		 */
+		put_device(&md->dev);
+		goto device_register_err;
+	}
+
+	/* add shortcuts to improve code readability/compactness */
+	md->bus = bus;
+	bus->dev = &md->dev;
+	bus->md = md;
+
+device_register_err:
+	return ret;
+}
+
+/**
+ * sdw_master_device_del() - delete a Linux Master Device representation.
+ * @bus: bus handle
+ *
+ * This function is the dual of sdw_master_device_add()
+ */
+int sdw_master_device_del(struct sdw_bus *bus)
+{
+	device_unregister(bus->dev);
+
+	return 0;
+}