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// SPDX-License-Identifier: GPL-2.0
/*
* GPIO line mux which acts as virtual gpiochip and provides a 1-to-many
* mapping between virtual GPIOs and a real GPIO + multiplexer.
*
* Copyright (c) 2025 Jonas Jelonek <jelonek.jonas@gmail.com>
*/
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/mod_devicetable.h>
#include <linux/mutex.h>
#include <linux/mux/consumer.h>
#include <linux/platform_device.h>
#define MUX_SELECT_DELAY_US 100
struct gpio_lmux {
struct gpio_chip gc;
struct mux_control *mux;
struct gpio_desc *muxed_gpio;
u32 num_gpio_mux_states;
unsigned int gpio_mux_states[] __counted_by(num_gpio_mux_states);
};
static int gpio_lmux_gpio_get(struct gpio_chip *gc, unsigned int offset)
{
struct gpio_lmux *glm = gpiochip_get_data(gc);
int ret;
ret = mux_control_select_delay(glm->mux, glm->gpio_mux_states[offset],
MUX_SELECT_DELAY_US);
if (ret < 0)
return ret;
ret = gpiod_get_raw_value_cansleep(glm->muxed_gpio);
mux_control_deselect(glm->mux);
return ret;
}
static int gpio_lmux_gpio_get_direction(struct gpio_chip *gc,
unsigned int offset)
{
return GPIO_LINE_DIRECTION_IN;
}
static int gpio_lmux_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct gpio_lmux *glm;
unsigned int ngpio;
size_t size;
int ret;
ngpio = device_property_count_u32(dev, "gpio-line-mux-states");
if (!ngpio)
return -EINVAL;
size = struct_size(glm, gpio_mux_states, ngpio);
glm = devm_kzalloc(dev, size, GFP_KERNEL);
if (!glm)
return -ENOMEM;
glm->gc.base = -1;
glm->gc.can_sleep = true;
glm->gc.fwnode = dev_fwnode(dev);
glm->gc.label = dev_name(dev);
glm->gc.ngpio = ngpio;
glm->gc.owner = THIS_MODULE;
glm->gc.parent = dev;
glm->gc.get = gpio_lmux_gpio_get;
glm->gc.get_direction = gpio_lmux_gpio_get_direction;
glm->mux = devm_mux_control_get(dev, NULL);
if (IS_ERR(glm->mux))
return dev_err_probe(dev, PTR_ERR(glm->mux),
"could not get mux controller\n");
glm->muxed_gpio = devm_gpiod_get(dev, "muxed", GPIOD_IN);
if (IS_ERR(glm->muxed_gpio))
return dev_err_probe(dev, PTR_ERR(glm->muxed_gpio),
"could not get muxed-gpio\n");
glm->num_gpio_mux_states = ngpio;
ret = device_property_read_u32_array(dev, "gpio-line-mux-states",
&glm->gpio_mux_states[0], ngpio);
if (ret)
return dev_err_probe(dev, ret, "could not get mux states\n");
ret = devm_gpiochip_add_data(dev, &glm->gc, glm);
if (ret)
return dev_err_probe(dev, ret, "failed to add gpiochip\n");
return 0;
}
static const struct of_device_id gpio_lmux_of_match[] = {
{ .compatible = "gpio-line-mux" },
{ }
};
MODULE_DEVICE_TABLE(of, gpio_lmux_of_match);
static struct platform_driver gpio_lmux_driver = {
.driver = {
.name = "gpio-line-mux",
.of_match_table = gpio_lmux_of_match,
},
.probe = gpio_lmux_probe,
};
module_platform_driver(gpio_lmux_driver);
MODULE_AUTHOR("Jonas Jelonek <jelonek.jonas@gmail.com>");
MODULE_DESCRIPTION("GPIO line mux driver");
MODULE_LICENSE("GPL");
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