/*
 * General Purpose I2C multiplexer
 *
 * Copyright (C) 2017 Axentia Technologies AB
 *
 * Author: Peter Rosin <peda@axentia.se>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/module.h>
#include <linux/mux/consumer.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>

struct mux {
	struct mux_control *control;

	bool do_not_deselect;
};

static int i2c_mux_select(struct i2c_mux_core *muxc, u32 chan)
{
	struct mux *mux = i2c_mux_priv(muxc);
	int ret;

	ret = mux_control_select(mux->control, chan);
	mux->do_not_deselect = ret < 0;

	return ret;
}

static int i2c_mux_deselect(struct i2c_mux_core *muxc, u32 chan)
{
	struct mux *mux = i2c_mux_priv(muxc);

	if (mux->do_not_deselect)
		return 0;

	return mux_control_deselect(mux->control);
}

static struct i2c_adapter *mux_parent_adapter(struct device *dev)
{
	struct device_node *np = dev->of_node;
	struct device_node *parent_np;
	struct i2c_adapter *parent;

	parent_np = of_parse_phandle(np, "i2c-parent", 0);
	if (!parent_np) {
		dev_err(dev, "Cannot parse i2c-parent\n");
		return ERR_PTR(-ENODEV);
	}
	parent = of_find_i2c_adapter_by_node(parent_np);
	of_node_put(parent_np);
	if (!parent)
		return ERR_PTR(-EPROBE_DEFER);

	return parent;
}

static const struct of_device_id i2c_mux_of_match[] = {
	{ .compatible = "i2c-mux", },
	{},
};
MODULE_DEVICE_TABLE(of, i2c_mux_of_match);

static int i2c_mux_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct device_node *np = dev->of_node;
	struct device_node *child;
	struct i2c_mux_core *muxc;
	struct mux *mux;
	struct i2c_adapter *parent;
	int children;
	int ret;

	if (!np)
		return -ENODEV;

	mux = devm_kzalloc(dev, sizeof(*mux), GFP_KERNEL);
	if (!mux)
		return -ENOMEM;

	mux->control = devm_mux_control_get(dev, NULL);
	if (IS_ERR(mux->control)) {
		if (PTR_ERR(mux->control) != -EPROBE_DEFER)
			dev_err(dev, "failed to get control-mux\n");
		return PTR_ERR(mux->control);
	}

	parent = mux_parent_adapter(dev);
	if (IS_ERR(parent)) {
		if (PTR_ERR(parent) != -EPROBE_DEFER)
			dev_err(dev, "failed to get i2c-parent adapter\n");
		return PTR_ERR(parent);
	}

	children = of_get_child_count(np);

	muxc = i2c_mux_alloc(parent, dev, children, 0, 0,
			     i2c_mux_select, i2c_mux_deselect);
	if (!muxc) {
		ret = -ENOMEM;
		goto err_parent;
	}
	muxc->priv = mux;

	platform_set_drvdata(pdev, muxc);

	muxc->mux_locked = of_property_read_bool(np, "mux-locked");

	for_each_child_of_node(np, child) {
		u32 chan;

		ret = of_property_read_u32(child, "reg", &chan);
		if (ret < 0) {
			dev_err(dev, "no reg property for node '%s'\n",
				child->name);
			goto err_children;
		}

		if (chan >= mux_control_states(mux->control)) {
			dev_err(dev, "invalid reg %u\n", chan);
			ret = -EINVAL;
			goto err_children;
		}

		ret = i2c_mux_add_adapter(muxc, 0, chan, 0);
		if (ret)
			goto err_children;
	}

	dev_info(dev, "%d-port mux on %s adapter\n", children, parent->name);

	return 0;

err_children:
	of_node_put(child);
	i2c_mux_del_adapters(muxc);
err_parent:
	i2c_put_adapter(parent);

	return ret;
}

static int i2c_mux_remove(struct platform_device *pdev)
{
	struct i2c_mux_core *muxc = platform_get_drvdata(pdev);

	i2c_mux_del_adapters(muxc);
	i2c_put_adapter(muxc->parent);

	return 0;
}

static struct platform_driver i2c_mux_driver = {
	.probe	= i2c_mux_probe,
	.remove	= i2c_mux_remove,
	.driver	= {
		.name	= "i2c-mux-gpmux",
		.of_match_table = i2c_mux_of_match,
	},
};
module_platform_driver(i2c_mux_driver);

MODULE_DESCRIPTION("General Purpose I2C multiplexer driver");
MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
MODULE_LICENSE("GPL v2");