aboutsummaryrefslogtreecommitdiff
path: root/drivers/gpio/gpio-74x164.c
blob: c81224ff2dca988b69eaf54296713aad225f6935 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
/*
 *  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 {
	struct gpio_chip	gpio_chip;
	struct mutex		lock;
	u32			registers;
	/*
	 * 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 sent will end up in the last
	 * register at the end of the transfer. So, to have a logical
	 * numbering, store the bytes in reverse order.
	 */
	u8			buffer[0];
};

static int __gen_74x164_write_config(struct gen_74x164_chip *chip)
{
	struct spi_transfer xfer = {
		.tx_buf = chip->buffer,
		.len = chip->registers,
	};

	return spi_sync_transfer(to_spi_device(chip->gpio_chip.parent),
				 &xfer, 1);
}

static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
{
	struct gen_74x164_chip *chip = gpiochip_get_data(gc);
	u8 bank = chip->registers - 1 - 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 = gpiochip_get_data(gc);
	u8 bank = chip->registers - 1 - 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;
	u32 nregs;
	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;

	if (of_property_read_u32(spi->dev.of_node, "registers-number",
				 &nregs)) {
		dev_err(&spi->dev,
			"Missing registers-number property in the DT.\n");
		return -EINVAL;
	}

	chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, 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;

	chip->registers = nregs;
	chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;

	chip->gpio_chip.can_sleep = true;
	chip->gpio_chip.parent = &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_data(&chip->gpio_chip, 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);

	gpiochip_remove(&chip->gpio_chip);
	mutex_destroy(&chip->lock);

	return 0;
}

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",
		.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");