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i2c: Add generic I2C multiplexer using GPIO API
Add an i2c mux driver providing access to i2c bus segments using a hardware MUX sitting on a master bus and controlled through gpio pins. E.G. something like: ---------- ---------- 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. Signed-off-by: Peter Korsgaard <peter.korsgaard@barco.com> Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Peter Korsgaard
Jean Delvare
parent
b18a5c80eb
commit
92ed1a76ca
65
Documentation/i2c/muxes/gpio-i2cmux
Normal file
65
Documentation/i2c/muxes/gpio-i2cmux
Normal file
@ -0,0 +1,65 @@
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Kernel driver gpio-i2cmux
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Author: Peter Korsgaard <peter.korsgaard@barco.com>
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Description
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-----------
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gpio-i2cmux is an i2c mux driver providing access to I2C bus segments
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from a master I2C bus and a hardware MUX controlled through GPIO pins.
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E.G.:
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---------- ---------- Bus segment 1 - - - - -
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| | SCL/SDA | |-------------- | |
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| |------------| |
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| | | | Bus segment 2 | |
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| Linux | GPIO 1..N | MUX |--------------- Devices
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| |------------| | | |
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| | | | Bus segment M
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| | | |---------------| |
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---------- ---------- - - - - -
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SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
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according to the settings of the GPIO pins 1..N.
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Usage
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-----
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gpio-i2cmux uses the platform bus, so you need to provide a struct
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platform_device with the platform_data pointing to a struct
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gpio_i2cmux_platform_data with the I2C adapter number of the master
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bus, the number of bus segments to create and the GPIO pins used
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to control it. See include/linux/gpio-i2cmux.h for details.
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E.G. something like this for a MUX providing 4 bus segments
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controlled through 3 GPIO pins:
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#include <linux/gpio-i2cmux.h>
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#include <linux/platform_device.h>
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static const unsigned myboard_gpiomux_gpios[] = {
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AT91_PIN_PC26, AT91_PIN_PC25, AT91_PIN_PC24
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};
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static const unsigned myboard_gpiomux_values[] = {
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0, 1, 2, 3
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};
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static struct gpio_i2cmux_platform_data myboard_i2cmux_data = {
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.parent = 1,
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.base_nr = 2, /* optional */
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.values = myboard_gpiomux_values,
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.n_values = ARRAY_SIZE(myboard_gpiomux_values),
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.gpios = myboard_gpiomux_gpios,
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.n_gpios = ARRAY_SIZE(myboard_gpiomux_gpios),
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.idle = 4, /* optional */
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};
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static struct platform_device myboard_i2cmux = {
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.name = "gpio-i2cmux",
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.id = 0,
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.dev = {
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.platform_data = &myboard_i2cmux_data,
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},
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};
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@ -2608,6 +2608,14 @@ S: Supported
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F: drivers/i2c/busses/i2c-gpio.c
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F: include/linux/i2c-gpio.h
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GENERIC GPIO I2C MULTIPLEXER DRIVER
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M: Peter Korsgaard <peter.korsgaard@barco.com>
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L: linux-i2c@vger.kernel.org
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S: Supported
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F: drivers/i2c/muxes/gpio-i2cmux.c
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F: include/linux/gpio-i2cmux.h
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F: Documentation/i2c/muxes/gpio-i2cmux
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GENERIC HDLC (WAN) DRIVERS
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M: Krzysztof Halasa <khc@pm.waw.pl>
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W: http://www.kernel.org/pub/linux/utils/net/hdlc/
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@ -5,6 +5,18 @@
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menu "Multiplexer I2C Chip support"
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depends on I2C_MUX
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config I2C_MUX_GPIO
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tristate "GPIO-based I2C multiplexer"
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depends on GENERIC_GPIO
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help
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If you say yes to this option, support will be included for a
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GPIO based I2C multiplexer. This driver provides access to
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I2C busses connected through a MUX, which is controlled
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through GPIO pins.
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This driver can also be built as a module. If so, the module
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will be called gpio-i2cmux.
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config I2C_MUX_PCA9541
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tristate "NXP PCA9541 I2C Master Selector"
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depends on EXPERIMENTAL
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@ -1,6 +1,7 @@
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#
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# Makefile for multiplexer I2C chip drivers.
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obj-$(CONFIG_I2C_MUX_GPIO) += gpio-i2cmux.o
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obj-$(CONFIG_I2C_MUX_PCA9541) += pca9541.o
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obj-$(CONFIG_I2C_MUX_PCA954x) += pca954x.o
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184
drivers/i2c/muxes/gpio-i2cmux.c
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184
drivers/i2c/muxes/gpio-i2cmux.c
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@ -0,0 +1,184 @@
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/*
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* I2C multiplexer using GPIO API
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*
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* Peter Korsgaard <peter.korsgaard@barco.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/i2c.h>
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#include <linux/i2c-mux.h>
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#include <linux/gpio-i2cmux.h>
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#include <linux/platform_device.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/gpio.h>
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struct gpiomux {
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struct i2c_adapter *parent;
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struct i2c_adapter **adap; /* child busses */
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struct gpio_i2cmux_platform_data data;
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};
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static void gpiomux_set(const struct gpiomux *mux, unsigned val)
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{
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int i;
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for (i = 0; i < mux->data.n_gpios; i++)
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gpio_set_value(mux->data.gpios[i], val & (1 << i));
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}
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static int gpiomux_select(struct i2c_adapter *adap, void *data, u32 chan)
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{
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struct gpiomux *mux = data;
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gpiomux_set(mux, mux->data.values[chan]);
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return 0;
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}
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static int gpiomux_deselect(struct i2c_adapter *adap, void *data, u32 chan)
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{
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struct gpiomux *mux = data;
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gpiomux_set(mux, mux->data.idle);
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return 0;
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}
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static int __devinit gpiomux_probe(struct platform_device *pdev)
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{
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struct gpiomux *mux;
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struct gpio_i2cmux_platform_data *pdata;
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struct i2c_adapter *parent;
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int (*deselect) (struct i2c_adapter *, void *, u32);
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unsigned initial_state;
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int i, ret;
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pdata = pdev->dev.platform_data;
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if (!pdata) {
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dev_err(&pdev->dev, "Missing platform data\n");
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return -ENODEV;
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}
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parent = i2c_get_adapter(pdata->parent);
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if (!parent) {
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dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
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pdata->parent);
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return -ENODEV;
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}
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mux = kzalloc(sizeof(*mux), GFP_KERNEL);
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if (!mux) {
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ret = -ENOMEM;
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goto alloc_failed;
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}
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mux->parent = parent;
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mux->data = *pdata;
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mux->adap = kzalloc(sizeof(struct i2c_adapter *) * pdata->n_values,
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GFP_KERNEL);
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if (!mux->adap) {
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ret = -ENOMEM;
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goto alloc_failed2;
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}
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if (pdata->idle != GPIO_I2CMUX_NO_IDLE) {
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initial_state = pdata->idle;
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deselect = gpiomux_deselect;
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} else {
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initial_state = pdata->values[0];
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deselect = NULL;
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}
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for (i = 0; i < pdata->n_gpios; i++) {
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ret = gpio_request(pdata->gpios[i], "gpio-i2cmux");
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if (ret)
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goto err_request_gpio;
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gpio_direction_output(pdata->gpios[i],
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initial_state & (1 << i));
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}
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for (i = 0; i < pdata->n_values; i++) {
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u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
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mux->adap[i] = i2c_add_mux_adapter(parent, mux, nr, i,
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gpiomux_select, deselect);
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if (!mux->adap[i]) {
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ret = -ENODEV;
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dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
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goto add_adapter_failed;
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}
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}
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dev_info(&pdev->dev, "%d port mux on %s adapter\n",
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pdata->n_values, parent->name);
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platform_set_drvdata(pdev, mux);
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return 0;
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add_adapter_failed:
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for (; i > 0; i--)
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i2c_del_mux_adapter(mux->adap[i - 1]);
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i = pdata->n_gpios;
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err_request_gpio:
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for (; i > 0; i--)
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gpio_free(pdata->gpios[i - 1]);
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kfree(mux->adap);
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alloc_failed2:
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kfree(mux);
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alloc_failed:
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i2c_put_adapter(parent);
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return ret;
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}
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static int __devexit gpiomux_remove(struct platform_device *pdev)
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{
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struct gpiomux *mux = platform_get_drvdata(pdev);
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int i;
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for (i = 0; i < mux->data.n_values; i++)
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i2c_del_mux_adapter(mux->adap[i]);
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for (i = 0; i < mux->data.n_gpios; i++)
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gpio_free(mux->data.gpios[i]);
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platform_set_drvdata(pdev, NULL);
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i2c_put_adapter(mux->parent);
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kfree(mux->adap);
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kfree(mux);
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return 0;
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}
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static struct platform_driver gpiomux_driver = {
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.probe = gpiomux_probe,
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.remove = __devexit_p(gpiomux_remove),
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.driver = {
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.owner = THIS_MODULE,
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.name = "gpio-i2cmux",
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},
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};
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static int __init gpiomux_init(void)
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{
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return platform_driver_register(&gpiomux_driver);
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}
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static void __exit gpiomux_exit(void)
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{
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platform_driver_unregister(&gpiomux_driver);
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}
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module_init(gpiomux_init);
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module_exit(gpiomux_exit);
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MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
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MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@barco.com>");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:gpio-i2cmux");
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38
include/linux/gpio-i2cmux.h
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38
include/linux/gpio-i2cmux.h
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@ -0,0 +1,38 @@
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/*
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* gpio-i2cmux interface to platform code
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*
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* Peter Korsgaard <peter.korsgaard@barco.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _LINUX_GPIO_I2CMUX_H
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#define _LINUX_GPIO_I2CMUX_H
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/* MUX has no specific idle mode */
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#define GPIO_I2CMUX_NO_IDLE ((unsigned)-1)
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/**
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* struct gpio_i2cmux_platform_data - Platform-dependent data for gpio-i2cmux
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* @parent: Parent I2C bus adapter number
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* @base_nr: Base I2C bus number to number adapters from or zero for dynamic
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* @values: Array of bitmasks of GPIO settings (low/high) for each
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* position
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* @n_values: Number of multiplexer positions (busses to instantiate)
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* @gpios: Array of GPIO numbers used to control MUX
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* @n_gpios: Number of GPIOs used to control MUX
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* @idle: Bitmask to write to MUX when idle or GPIO_I2CMUX_NO_IDLE if not used
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*/
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struct gpio_i2cmux_platform_data {
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int parent;
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int base_nr;
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const unsigned *values;
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int n_values;
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const unsigned *gpios;
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int n_gpios;
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unsigned idle;
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};
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#endif /* _LINUX_GPIO_I2CMUX_H */
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