1/*
  2 * I2C multiplexer using GPIO API
  3 *
  4 * Peter Korsgaard <peter.korsgaard@barco.com>
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License version 2 as
  8 * published by the Free Software Foundation.
  9 */
 10
 11#include <linux/i2c.h>
 12#include <linux/i2c-mux.h>
 13#include <linux/gpio-i2cmux.h>
 14#include <linux/platform_device.h>
 15#include <linux/init.h>
 16#include <linux/module.h>
 17#include <linux/slab.h>
 18#include <linux/gpio.h>
 19
 20struct gpiomux {
 21	struct i2c_adapter *parent;
 22	struct i2c_adapter **adap; /* child busses */
 23	struct gpio_i2cmux_platform_data data;
 24};
 25
 26static void gpiomux_set(const struct gpiomux *mux, unsigned val)
 27{
 28	int i;
 29
 30	for (i = 0; i < mux->data.n_gpios; i++)
 31		gpio_set_value(mux->data.gpios[i], val & (1 << i));
 32}
 33
 34static int gpiomux_select(struct i2c_adapter *adap, void *data, u32 chan)
 35{
 36	struct gpiomux *mux = data;
 37
 38	gpiomux_set(mux, mux->data.values[chan]);
 39
 40	return 0;
 41}
 42
 43static int gpiomux_deselect(struct i2c_adapter *adap, void *data, u32 chan)
 44{
 45	struct gpiomux *mux = data;
 46
 47	gpiomux_set(mux, mux->data.idle);
 48
 49	return 0;
 50}
 51
 52static int __devinit gpiomux_probe(struct platform_device *pdev)
 53{
 54	struct gpiomux *mux;
 55	struct gpio_i2cmux_platform_data *pdata;
 56	struct i2c_adapter *parent;
 57	int (*deselect) (struct i2c_adapter *, void *, u32);
 58	unsigned initial_state;
 59	int i, ret;
 60
 61	pdata = pdev->dev.platform_data;
 62	if (!pdata) {
 63		dev_err(&pdev->dev, "Missing platform data\n");
 64		return -ENODEV;
 65	}
 66
 67	parent = i2c_get_adapter(pdata->parent);
 68	if (!parent) {
 69		dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
 70			pdata->parent);
 71		return -ENODEV;
 72	}
 73
 74	mux = kzalloc(sizeof(*mux), GFP_KERNEL);
 75	if (!mux) {
 76		ret = -ENOMEM;
 77		goto alloc_failed;
 78	}
 79
 80	mux->parent = parent;
 81	mux->data = *pdata;
 82	mux->adap = kzalloc(sizeof(struct i2c_adapter *) * pdata->n_values,
 83			    GFP_KERNEL);
 84	if (!mux->adap) {
 85		ret = -ENOMEM;
 86		goto alloc_failed2;
 87	}
 88
 89	if (pdata->idle != GPIO_I2CMUX_NO_IDLE) {
 90		initial_state = pdata->idle;
 91		deselect = gpiomux_deselect;
 92	} else {
 93		initial_state = pdata->values[0];
 94		deselect = NULL;
 95	}
 96
 97	for (i = 0; i < pdata->n_gpios; i++) {
 98		ret = gpio_request(pdata->gpios[i], "gpio-i2cmux");
 99		if (ret)
100			goto err_request_gpio;
101		gpio_direction_output(pdata->gpios[i],
102				      initial_state & (1 << i));
103	}
104
105	for (i = 0; i < pdata->n_values; i++) {
106		u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
107
108		mux->adap[i] = i2c_add_mux_adapter(parent, mux, nr, i,
109						   gpiomux_select, deselect);
110		if (!mux->adap[i]) {
111			ret = -ENODEV;
112			dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
113			goto add_adapter_failed;
114		}
115	}
116
117	dev_info(&pdev->dev, "%d port mux on %s adapter\n",
118		 pdata->n_values, parent->name);
119
120	platform_set_drvdata(pdev, mux);
121
122	return 0;
123
124add_adapter_failed:
125	for (; i > 0; i--)
126		i2c_del_mux_adapter(mux->adap[i - 1]);
127	i = pdata->n_gpios;
128err_request_gpio:
129	for (; i > 0; i--)
130		gpio_free(pdata->gpios[i - 1]);
131	kfree(mux->adap);
132alloc_failed2:
133	kfree(mux);
134alloc_failed:
135	i2c_put_adapter(parent);
136
137	return ret;
138}
139
140static int __devexit gpiomux_remove(struct platform_device *pdev)
141{
142	struct gpiomux *mux = platform_get_drvdata(pdev);
143	int i;
144
145	for (i = 0; i < mux->data.n_values; i++)
146		i2c_del_mux_adapter(mux->adap[i]);
147
148	for (i = 0; i < mux->data.n_gpios; i++)
149		gpio_free(mux->data.gpios[i]);
150
151	platform_set_drvdata(pdev, NULL);
152	i2c_put_adapter(mux->parent);
153	kfree(mux->adap);
154	kfree(mux);
155
156	return 0;
157}
158
159static struct platform_driver gpiomux_driver = {
160	.probe	= gpiomux_probe,
161	.remove	= __devexit_p(gpiomux_remove),
162	.driver	= {
163		.owner	= THIS_MODULE,
164		.name	= "gpio-i2cmux",
165	},
166};
167
168static int __init gpiomux_init(void)
169{
170	return platform_driver_register(&gpiomux_driver);
171}
172
173static void __exit gpiomux_exit(void)
174{
175	platform_driver_unregister(&gpiomux_driver);
176}
177
178module_init(gpiomux_init);
179module_exit(gpiomux_exit);
180
181MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
182MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@barco.com>");
183MODULE_LICENSE("GPL");
184MODULE_ALIAS("platform:gpio-i2cmux");