2 * 74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
4 * Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
5 * Copyright (C) 2010 Miguel Gaio <miguel.gaio@efixo.com>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/init.h>
13 #include <linux/mutex.h>
14 #include <linux/spi/spi.h>
15 #include <linux/gpio.h>
16 #include <linux/of_gpio.h>
17 #include <linux/slab.h>
18 #include <linux/module.h>
20 #define GEN_74X164_NUMBER_GPIOS 8
22 struct gen_74x164_chip {
23 struct gpio_chip gpio_chip;
27 * Since the registers are chained, every byte sent will make
28 * the previous byte shift to the next register in the
29 * chain. Thus, the first byte sent will end up in the last
30 * register at the end of the transfer. So, to have a logical
31 * numbering, store the bytes in reverse order.
36 static struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc)
38 return container_of(gc, struct gen_74x164_chip, gpio_chip);
41 static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
43 struct spi_transfer xfer = {
44 .tx_buf = chip->buffer,
45 .len = chip->registers,
48 return spi_sync_transfer(to_spi_device(chip->gpio_chip.parent),
52 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
54 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
55 u8 bank = chip->registers - 1 - offset / 8;
59 mutex_lock(&chip->lock);
60 ret = (chip->buffer[bank] >> pin) & 0x1;
61 mutex_unlock(&chip->lock);
66 static void gen_74x164_set_value(struct gpio_chip *gc,
67 unsigned offset, int val)
69 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc);
70 u8 bank = chip->registers - 1 - offset / 8;
73 mutex_lock(&chip->lock);
75 chip->buffer[bank] |= (1 << pin);
77 chip->buffer[bank] &= ~(1 << pin);
79 __gen_74x164_write_config(chip);
80 mutex_unlock(&chip->lock);
83 static int gen_74x164_direction_output(struct gpio_chip *gc,
84 unsigned offset, int val)
86 gen_74x164_set_value(gc, offset, val);
90 static int gen_74x164_probe(struct spi_device *spi)
92 struct gen_74x164_chip *chip;
97 * bits_per_word cannot be configured in platform data
99 spi->bits_per_word = 8;
101 ret = spi_setup(spi);
105 if (of_property_read_u32(spi->dev.of_node, "registers-number",
108 "Missing registers-number property in the DT.\n");
112 chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL);
116 spi_set_drvdata(spi, chip);
118 chip->gpio_chip.label = spi->modalias;
119 chip->gpio_chip.direction_output = gen_74x164_direction_output;
120 chip->gpio_chip.get = gen_74x164_get_value;
121 chip->gpio_chip.set = gen_74x164_set_value;
122 chip->gpio_chip.base = -1;
124 chip->registers = nregs;
125 chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
127 chip->gpio_chip.can_sleep = true;
128 chip->gpio_chip.parent = &spi->dev;
129 chip->gpio_chip.owner = THIS_MODULE;
131 mutex_init(&chip->lock);
133 ret = __gen_74x164_write_config(chip);
135 dev_err(&spi->dev, "Failed writing: %d\n", ret);
139 ret = gpiochip_add(&chip->gpio_chip);
144 mutex_destroy(&chip->lock);
149 static int gen_74x164_remove(struct spi_device *spi)
151 struct gen_74x164_chip *chip = spi_get_drvdata(spi);
153 gpiochip_remove(&chip->gpio_chip);
154 mutex_destroy(&chip->lock);
159 static const struct of_device_id gen_74x164_dt_ids[] = {
160 { .compatible = "fairchild,74hc595" },
163 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids);
165 static struct spi_driver gen_74x164_driver = {
168 .of_match_table = gen_74x164_dt_ids,
170 .probe = gen_74x164_probe,
171 .remove = gen_74x164_remove,
173 module_spi_driver(gen_74x164_driver);
175 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
176 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
177 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
178 MODULE_LICENSE("GPL v2");