gpio-74x164.c
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/*
* 74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
*
* Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
* Copyright (C) 2010 Miguel Gaio <miguel.gaio@efixo.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/init.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#include <linux/slab.h>
#include <linux/module.h>
#define GEN_74X164_NUMBER_GPIOS 8
struct gen_74x164_chip {
u8 *buffer;
struct gpio_chip gpio_chip;
struct mutex lock;
u32 registers;
};
static struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc)
{
return container_of(gc, struct gen_74x164_chip, gpio_chip);
}
static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
{
struct spi_device *spi = to_spi_device(chip->gpio_chip.dev);
struct spi_message message;
struct spi_transfer *msg_buf;
int i, ret = 0;
msg_buf = kzalloc(chip->registers * sizeof(struct spi_transfer),
GFP_KERNEL);
if (!msg_buf)
return -ENOMEM;
spi_message_init(&message);
/*
* Since the registers are chained, every byte sent will make
* the previous byte shift to the next register in the
* chain. Thus, the first byte send will end up in the last
* register at the end of the transfer. So, to have a logical
* numbering, send the bytes in reverse order so that the last
* byte of the buffer will end up in the last register.
*/
for (i = chip->registers - 1; i >= 0; i--) {
msg_buf[i].tx_buf = chip->buffer + i;
msg_buf[i].len = sizeof(u8);
spi_message_add_tail(msg_buf + i, &message);
}
ret = spi_sync(spi, &message);
kfree(msg_buf);
return ret;
}
static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
{
struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
u8 bank = offset / 8;
u8 pin = offset % 8;
int ret;
mutex_lock(&chip->lock);
ret = (chip->buffer[bank] >> pin) & 0x1;
mutex_unlock(&chip->lock);
return ret;
}
static void gen_74x164_set_value(struct gpio_chip *gc,
unsigned offset, int val)
{
struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
u8 bank = offset / 8;
u8 pin = offset % 8;
mutex_lock(&chip->lock);
if (val)
chip->buffer[bank] |= (1 << pin);
else
chip->buffer[bank] &= ~(1 << pin);
__gen_74x164_write_config(chip);
mutex_unlock(&chip->lock);
}
static int gen_74x164_direction_output(struct gpio_chip *gc,
unsigned offset, int val)
{
gen_74x164_set_value(gc, offset, val);
return 0;
}
static int gen_74x164_probe(struct spi_device *spi)
{
struct gen_74x164_chip *chip;
int ret;
/*
* bits_per_word cannot be configured in platform data
*/
spi->bits_per_word = 8;
ret = spi_setup(spi);
if (ret < 0)
return ret;
chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
if (!chip)
return -ENOMEM;
spi_set_drvdata(spi, chip);
chip->gpio_chip.label = spi->modalias;
chip->gpio_chip.direction_output = gen_74x164_direction_output;
chip->gpio_chip.get = gen_74x164_get_value;
chip->gpio_chip.set = gen_74x164_set_value;
chip->gpio_chip.base = -1;
if (of_property_read_u32(spi->dev.of_node, "registers-number",
&chip->registers)) {
dev_err(&spi->dev,
"Missing registers-number property in the DT.\n");
return -EINVAL;
}
chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
chip->buffer = devm_kzalloc(&spi->dev, chip->registers, GFP_KERNEL);
if (!chip->buffer)
return -ENOMEM;
chip->gpio_chip.can_sleep = true;
chip->gpio_chip.dev = &spi->dev;
chip->gpio_chip.owner = THIS_MODULE;
mutex_init(&chip->lock);
ret = __gen_74x164_write_config(chip);
if (ret) {
dev_err(&spi->dev, "Failed writing: %d\n", ret);
goto exit_destroy;
}
ret = gpiochip_add(&chip->gpio_chip);
if (!ret)
return 0;
exit_destroy:
mutex_destroy(&chip->lock);
return ret;
}
static int gen_74x164_remove(struct spi_device *spi)
{
struct gen_74x164_chip *chip = spi_get_drvdata(spi);
int ret;
ret = gpiochip_remove(&chip->gpio_chip);
if (!ret)
mutex_destroy(&chip->lock);
return ret;
}
static const struct of_device_id gen_74x164_dt_ids[] = {
{ .compatible = "fairchild,74hc595" },
{},
};
MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);
static struct spi_driver gen_74x164_driver = {
.driver = {
.name = "74x164",
.owner = THIS_MODULE,
.of_match_table = gen_74x164_dt_ids,
},
.probe = gen_74x164_probe,
.remove = gen_74x164_remove,
};
module_spi_driver(gen_74x164_driver);
MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
MODULE_LICENSE("GPL v2");