--- /dev/null
+Kernel driver gpio-i2cmux
+
+Author: Peter Korsgaard <peter.korsgaard@barco.com>
+
+Description
+-----------
+
+gpio-i2cmux is an i2c mux driver providing access to I2C bus segments
+from a master I2C bus and a hardware MUX controlled through GPIO pins.
+
+E.G.:
+
+ ---------- ---------- Bus segment 1 - - - - -
+ | | SCL/SDA | |-------------- | |
+ | |------------| |
+ | | | | Bus segment 2 | |
+ | Linux | GPIO 1..N | MUX |--------------- Devices
+ | |------------| | | |
+ | | | | Bus segment M
+ | | | |---------------| |
+ ---------- ---------- - - - - -
+
+SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
+according to the settings of the GPIO pins 1..N.
+
+Usage
+-----
+
+gpio-i2cmux uses the platform bus, so you need to provide a struct
+platform_device with the platform_data pointing to a struct
+gpio_i2cmux_platform_data with the I2C adapter number of the master
+bus, the number of bus segments to create and the GPIO pins used
+to control it. See include/linux/gpio-i2cmux.h for details.
+
+E.G. something like this for a MUX providing 4 bus segments
+controlled through 3 GPIO pins:
+
+#include <linux/gpio-i2cmux.h>
+#include <linux/platform_device.h>
+
+static const unsigned myboard_gpiomux_gpios[] = {
+ AT91_PIN_PC26, AT91_PIN_PC25, AT91_PIN_PC24
+};
+
+static const unsigned myboard_gpiomux_values[] = {
+ 0, 1, 2, 3
+};
+
+static struct gpio_i2cmux_platform_data myboard_i2cmux_data = {
+ .parent = 1,
+ .base_nr = 2, /* optional */
+ .values = myboard_gpiomux_values,
+ .n_values = ARRAY_SIZE(myboard_gpiomux_values),
+ .gpios = myboard_gpiomux_gpios,
+ .n_gpios = ARRAY_SIZE(myboard_gpiomux_gpios),
+ .idle = 4, /* optional */
+};
+
+static struct platform_device myboard_i2cmux = {
+ .name = "gpio-i2cmux",
+ .id = 0,
+ .dev = {
+ .platform_data = &myboard_i2cmux_data,
+ },
+};
--- /dev/null
+/*
+ * I2C multiplexer using GPIO API
+ *
+ * Peter Korsgaard <peter.korsgaard@barco.com>
+ *
+ * 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/gpio-i2cmux.h>
+#include <linux/platform_device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/gpio.h>
+
+struct gpiomux {
+ struct i2c_adapter *parent;
+ struct i2c_adapter **adap; /* child busses */
+ struct gpio_i2cmux_platform_data data;
+};
+
+static void gpiomux_set(const struct gpiomux *mux, unsigned val)
+{
+ int i;
+
+ for (i = 0; i < mux->data.n_gpios; i++)
+ gpio_set_value(mux->data.gpios[i], val & (1 << i));
+}
+
+static int gpiomux_select(struct i2c_adapter *adap, void *data, u32 chan)
+{
+ struct gpiomux *mux = data;
+
+ gpiomux_set(mux, mux->data.values[chan]);
+
+ return 0;
+}
+
+static int gpiomux_deselect(struct i2c_adapter *adap, void *data, u32 chan)
+{
+ struct gpiomux *mux = data;
+
+ gpiomux_set(mux, mux->data.idle);
+
+ return 0;
+}
+
+static int __devinit gpiomux_probe(struct platform_device *pdev)
+{
+ struct gpiomux *mux;
+ struct gpio_i2cmux_platform_data *pdata;
+ struct i2c_adapter *parent;
+ int (*deselect) (struct i2c_adapter *, void *, u32);
+ unsigned initial_state;
+ int i, ret;
+
+ pdata = pdev->dev.platform_data;
+ if (!pdata) {
+ dev_err(&pdev->dev, "Missing platform data\n");
+ return -ENODEV;
+ }
+
+ parent = i2c_get_adapter(pdata->parent);
+ if (!parent) {
+ dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
+ pdata->parent);
+ return -ENODEV;
+ }
+
+ mux = kzalloc(sizeof(*mux), GFP_KERNEL);
+ if (!mux) {
+ ret = -ENOMEM;
+ goto alloc_failed;
+ }
+
+ mux->parent = parent;
+ mux->data = *pdata;
+ mux->adap = kzalloc(sizeof(struct i2c_adapter *) * pdata->n_values,
+ GFP_KERNEL);
+ if (!mux->adap) {
+ ret = -ENOMEM;
+ goto alloc_failed2;
+ }
+
+ if (pdata->idle != GPIO_I2CMUX_NO_IDLE) {
+ initial_state = pdata->idle;
+ deselect = gpiomux_deselect;
+ } else {
+ initial_state = pdata->values[0];
+ deselect = NULL;
+ }
+
+ for (i = 0; i < pdata->n_gpios; i++) {
+ ret = gpio_request(pdata->gpios[i], "gpio-i2cmux");
+ if (ret)
+ goto err_request_gpio;
+ gpio_direction_output(pdata->gpios[i],
+ initial_state & (1 << i));
+ }
+
+ for (i = 0; i < pdata->n_values; i++) {
+ u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
+
+ mux->adap[i] = i2c_add_mux_adapter(parent, mux, nr, i,
+ gpiomux_select, deselect);
+ if (!mux->adap[i]) {
+ ret = -ENODEV;
+ dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
+ goto add_adapter_failed;
+ }
+ }
+
+ dev_info(&pdev->dev, "%d port mux on %s adapter\n",
+ pdata->n_values, parent->name);
+
+ platform_set_drvdata(pdev, mux);
+
+ return 0;
+
+add_adapter_failed:
+ for (; i > 0; i--)
+ i2c_del_mux_adapter(mux->adap[i - 1]);
+ i = pdata->n_gpios;
+err_request_gpio:
+ for (; i > 0; i--)
+ gpio_free(pdata->gpios[i - 1]);
+ kfree(mux->adap);
+alloc_failed2:
+ kfree(mux);
+alloc_failed:
+ i2c_put_adapter(parent);
+
+ return ret;
+}
+
+static int __devexit gpiomux_remove(struct platform_device *pdev)
+{
+ struct gpiomux *mux = platform_get_drvdata(pdev);
+ int i;
+
+ for (i = 0; i < mux->data.n_values; i++)
+ i2c_del_mux_adapter(mux->adap[i]);
+
+ for (i = 0; i < mux->data.n_gpios; i++)
+ gpio_free(mux->data.gpios[i]);
+
+ platform_set_drvdata(pdev, NULL);
+ i2c_put_adapter(mux->parent);
+ kfree(mux->adap);
+ kfree(mux);
+
+ return 0;
+}
+
+static struct platform_driver gpiomux_driver = {
+ .probe = gpiomux_probe,
+ .remove = __devexit_p(gpiomux_remove),
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "gpio-i2cmux",
+ },
+};
+
+static int __init gpiomux_init(void)
+{
+ return platform_driver_register(&gpiomux_driver);
+}
+
+static void __exit gpiomux_exit(void)
+{
+ platform_driver_unregister(&gpiomux_driver);
+}
+
+module_init(gpiomux_init);
+module_exit(gpiomux_exit);
+
+MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
+MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@barco.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:gpio-i2cmux");
--- /dev/null
+/*
+ * gpio-i2cmux interface to platform code
+ *
+ * Peter Korsgaard <peter.korsgaard@barco.com>
+ *
+ * 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.
+ */
+
+#ifndef _LINUX_GPIO_I2CMUX_H
+#define _LINUX_GPIO_I2CMUX_H
+
+/* MUX has no specific idle mode */
+#define GPIO_I2CMUX_NO_IDLE ((unsigned)-1)
+
+/**
+ * struct gpio_i2cmux_platform_data - Platform-dependent data for gpio-i2cmux
+ * @parent: Parent I2C bus adapter number
+ * @base_nr: Base I2C bus number to number adapters from or zero for dynamic
+ * @values: Array of bitmasks of GPIO settings (low/high) for each
+ * position
+ * @n_values: Number of multiplexer positions (busses to instantiate)
+ * @gpios: Array of GPIO numbers used to control MUX
+ * @n_gpios: Number of GPIOs used to control MUX
+ * @idle: Bitmask to write to MUX when idle or GPIO_I2CMUX_NO_IDLE if not used
+ */
+struct gpio_i2cmux_platform_data {
+ int parent;
+ int base_nr;
+ const unsigned *values;
+ int n_values;
+ const unsigned *gpios;
+ int n_gpios;
+ unsigned idle;
+};
+
+#endif /* _LINUX_GPIO_I2CMUX_H */
projects / linux-flexiantxendom0-natty.git / commitdiff