Add an i2c mux driver providing virtual i2c busses using a hardware MUX sitting on a master bus and controlled through gpio pins.
E.G. something like: ---------- ---------- Virtual bus 1 - - - - - | | SCL/SDA | |-------------- | | | |------------| | | | | | Virtual bus 2 | | | Linux | GPIO 1..N | MUX |--------------- Devices | |------------| | | | | | | | Virtual bus M | | | |---------------| | ---------- ---------- - - - - - SCL/SDA of the master I2C bus is multiplexed to virtual bus 1..M according to the settings of the GPIO pins 1..N. Signed-off-by: Peter Korsgaard <[email protected]> --- Changes since v2: - Adjust according to Jean's comments, rename to gpio-i2cmux Changes since v1: - Use i2c-mux infrastructure - Move to drivers/i2c/muxes Documentation/i2c/muxes/gpio-i2cmux | 65 +++++++++++++ MAINTAINERS | 7 ++ drivers/i2c/muxes/Kconfig | 12 +++ drivers/i2c/muxes/Makefile | 1 + drivers/i2c/muxes/gpio-i2cmux.c | 175 +++++++++++++++++++++++++++++++++++ include/linux/gpio-i2cmux.h | 35 +++++++ 6 files changed, 295 insertions(+), 0 deletions(-) create mode 100644 Documentation/i2c/muxes/gpio-i2cmux create mode 100644 drivers/i2c/muxes/gpio-i2cmux.c create mode 100644 include/linux/gpio-i2cmux.h diff --git a/Documentation/i2c/muxes/gpio-i2cmux b/Documentation/i2c/muxes/gpio-i2cmux new file mode 100644 index 0000000..a1768d3 --- /dev/null +++ b/Documentation/i2c/muxes/gpio-i2cmux @@ -0,0 +1,65 @@ +Kernel driver gpio-i2cmux + +Author: Peter Korsgaard <[email protected]> + +Description +----------- + +gpio-i2cmux is an i2c mux driver providing virtual I2C busses from a +master I2C bus and a hardware MUX controlled through GPIO pins. + +E.G.: + + ---------- ---------- Virtual bus 1 - - - - - + | | SCL/SDA | |-------------- | | + | |------------| | + | | | | Virtual bus 2 | | + | Linux | GPIO 1..N | MUX |--------------- Devices + | |------------| | | | + | | | | Virtual bus M + | | | |---------------| | + ---------- ---------- - - - - - + +SCL/SDA of the master I2C bus is multiplexed to virtual bus 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 virtual busses 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 virtual busses +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), + .gpio = myboard_gpiomux_gpios, + .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, + }, +}; diff --git a/MAINTAINERS b/MAINTAINERS index b3be8b3..8117a3f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2579,6 +2579,13 @@ S: Supported F: drivers/i2c/busses/i2c-gpio.c F: include/linux/i2c-gpio.h +GENERIC GPIO I2C MULTIPLEXER DRIVER +M: Peter Korsgaard <[email protected]> +L: [email protected] +S: Supported +F: drivers/i2c/muxes/gpio-i2cmux.c +F: include/linux/gpio-i2mux.h + GENERIC HDLC (WAN) DRIVERS M: Krzysztof Halasa <[email protected]> W: http://www.kernel.org/pub/linux/utils/net/hdlc/ diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig index 4d91d80..394a8b1 100644 --- a/drivers/i2c/muxes/Kconfig +++ b/drivers/i2c/muxes/Kconfig @@ -25,4 +25,16 @@ config I2C_MUX_PCA954x This driver can also be built as a module. If so, the module will be called pca954x. + config I2C_MUX_GPIO + tristate "GPIO-based I2C multiplexer" + depends on GENERIC_GPIO + help + If you say yes to this option, support will be included for a + GPIO based I2C multiplexer. This driver provides access to + I2C busses connected through a MUX, which is controlled + through GPIO pins. + + This driver can also be built as a module. If so, the module + will be called gpio-i2cmux. + endmenu diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile index d743806..b9a56d9 100644 --- a/drivers/i2c/muxes/Makefile +++ b/drivers/i2c/muxes/Makefile @@ -3,5 +3,6 @@ obj-$(CONFIG_I2C_MUX_PCA9541) += pca9541.o obj-$(CONFIG_I2C_MUX_PCA954x) += pca954x.o +obj-$(CONFIG_I2C_MUX_GPIO) += gpio-i2cmux.o ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG diff --git a/drivers/i2c/muxes/gpio-i2cmux.c b/drivers/i2c/muxes/gpio-i2cmux.c new file mode 100644 index 0000000..3487aca --- /dev/null +++ b/drivers/i2c/muxes/gpio-i2cmux.c @@ -0,0 +1,175 @@ +/* + * I2C multiplexer using GPIO API + * + * Peter Korsgaard <[email protected]> + * + * 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 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; + } + + 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], pdata->idle & (1 << i)); + } + + for (i = 0; i < pdata->n_values; i++) { + u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0; + bool has_idle = (pdata->idle != (unsigned)-1); + + mux->adap[i] = + i2c_add_mux_adapter(parent, mux, nr, i, gpiomux_select, + has_idle ? gpiomux_deselect : NULL); + 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 <[email protected]>"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:gpio-i2cmux"); diff --git a/include/linux/gpio-i2cmux.h b/include/linux/gpio-i2cmux.h new file mode 100644 index 0000000..5ac3438 --- /dev/null +++ b/include/linux/gpio-i2cmux.h @@ -0,0 +1,35 @@ +/* + * gpio-i2cmux interface to platform code + * + * Peter Korsgaard <[email protected]> + * + * 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 + +/** + * 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 -1 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 */ -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
