linux/drivers/gpio/gpio-latch.c

// SPDX-License-Identifier: GPL-2.0
/*
 * GPIO latch driver
 *
 *  Copyright (C) 2022 Sascha Hauer <[email protected]>
 *
 * This driver implements a GPIO (or better GPO as there is no input)
 * multiplexer based on latches like this:
 *
 * CLK0 ----------------------.        ,--------.
 * CLK1 -------------------.  `--------|>    #0 |
 *                         |           |        |
 * OUT0 ----------------+--|-----------|D0    Q0|-----|<
 * OUT1 --------------+-|--|-----------|D1    Q1|-----|<
 * OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
 * OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
 * OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
 * OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
 * OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
 * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
 *        | | | | | | | |  |           `--------'
 *        | | | | | | | |  |
 *        | | | | | | | |  |           ,--------.
 *        | | | | | | | |  `-----------|>    #1 |
 *        | | | | | | | |              |        |
 *        | | | | | | | `--------------|D0    Q0|-----|<
 *        | | | | | | `----------------|D1    Q1|-----|<
 *        | | | | | `------------------|D2    Q2|-----|<
 *        | | | | `--------------------|D3    Q3|-----|<
 *        | | | `----------------------|D4    Q4|-----|<
 *        | | `------------------------|D5    Q5|-----|<
 *        | `--------------------------|D6    Q6|-----|<
 *        `----------------------------|D7    Q7|-----|<
 *                                     `--------'
 *
 * The above is just an example. The actual number of number of latches and
 * the number of inputs per latch is derived from the number of GPIOs given
 * in the corresponding device tree properties.
 */

#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/delay.h>

#include "gpiolib.h"

struct gpio_latch_priv { … };

static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
{ … }

static void gpio_latch_set_unlocked(struct gpio_latch_priv *priv,
				    void (*set)(struct gpio_desc *desc, int value),
				    unsigned int offset, bool val)
{ … }

static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
{ … }

static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
{ … }

static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches)
{ … }

/*
 * Some value which is still acceptable to delay in atomic context.
 * If we need to go higher we might have to switch to usleep_range(),
 * but that cannot ne used in atomic context and the driver would have
 * to be adjusted to support that.
 */
#define DURATION_NS_MAX …

static int gpio_latch_probe(struct platform_device *pdev)
{ … }

static const struct of_device_id gpio_latch_ids[] = …;
MODULE_DEVICE_TABLE(of, gpio_latch_ids);

static struct platform_driver gpio_latch_driver = …;
module_platform_driver(…) …;

MODULE_LICENSE(…) …;
MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;