1 /* 2 * 74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver 3 * 4 * Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org> 5 * Copyright (C) 2010 Miguel Gaio <miguel.gaio@efixo.com> 6 * 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. 10 */ 11 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> 19 20 #define GEN_74X164_NUMBER_GPIOS 8 21 22 struct gen_74x164_chip { 23 u8 *buffer; 24 struct gpio_chip gpio_chip; 25 struct mutex lock; 26 u32 registers; 27 }; 28 29 static struct gen_74x164_chip *gpio_to_74x164_chip(struct gpio_chip *gc) 30 { 31 return container_of(gc, struct gen_74x164_chip, gpio_chip); 32 } 33 34 static int __gen_74x164_write_config(struct gen_74x164_chip *chip) 35 { 36 struct spi_device *spi = to_spi_device(chip->gpio_chip.dev); 37 struct spi_message message; 38 struct spi_transfer *msg_buf; 39 int i, ret = 0; 40 41 msg_buf = kzalloc(chip->registers * sizeof(struct spi_transfer), 42 GFP_KERNEL); 43 if (!msg_buf) 44 return -ENOMEM; 45 46 spi_message_init(&message); 47 48 /* 49 * Since the registers are chained, every byte sent will make 50 * the previous byte shift to the next register in the 51 * chain. Thus, the first byte send will end up in the last 52 * register at the end of the transfer. So, to have a logical 53 * numbering, send the bytes in reverse order so that the last 54 * byte of the buffer will end up in the last register. 55 */ 56 for (i = chip->registers - 1; i >= 0; i--) { 57 msg_buf[i].tx_buf = chip->buffer + i; 58 msg_buf[i].len = sizeof(u8); 59 spi_message_add_tail(msg_buf + i, &message); 60 } 61 62 ret = spi_sync(spi, &message); 63 64 kfree(msg_buf); 65 66 return ret; 67 } 68 69 static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset) 70 { 71 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc); 72 u8 bank = offset / 8; 73 u8 pin = offset % 8; 74 int ret; 75 76 mutex_lock(&chip->lock); 77 ret = (chip->buffer[bank] >> pin) & 0x1; 78 mutex_unlock(&chip->lock); 79 80 return ret; 81 } 82 83 static void gen_74x164_set_value(struct gpio_chip *gc, 84 unsigned offset, int val) 85 { 86 struct gen_74x164_chip *chip = gpio_to_74x164_chip(gc); 87 u8 bank = offset / 8; 88 u8 pin = offset % 8; 89 90 mutex_lock(&chip->lock); 91 if (val) 92 chip->buffer[bank] |= (1 << pin); 93 else 94 chip->buffer[bank] &= ~(1 << pin); 95 96 __gen_74x164_write_config(chip); 97 mutex_unlock(&chip->lock); 98 } 99 100 static int gen_74x164_direction_output(struct gpio_chip *gc, 101 unsigned offset, int val) 102 { 103 gen_74x164_set_value(gc, offset, val); 104 return 0; 105 } 106 107 static int gen_74x164_probe(struct spi_device *spi) 108 { 109 struct gen_74x164_chip *chip; 110 int ret; 111 112 /* 113 * bits_per_word cannot be configured in platform data 114 */ 115 spi->bits_per_word = 8; 116 117 ret = spi_setup(spi); 118 if (ret < 0) 119 return ret; 120 121 chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL); 122 if (!chip) 123 return -ENOMEM; 124 125 spi_set_drvdata(spi, chip); 126 127 chip->gpio_chip.label = spi->modalias; 128 chip->gpio_chip.direction_output = gen_74x164_direction_output; 129 chip->gpio_chip.get = gen_74x164_get_value; 130 chip->gpio_chip.set = gen_74x164_set_value; 131 chip->gpio_chip.base = -1; 132 133 if (of_property_read_u32(spi->dev.of_node, "registers-number", 134 &chip->registers)) { 135 dev_err(&spi->dev, 136 "Missing registers-number property in the DT.\n"); 137 return -EINVAL; 138 } 139 140 chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers; 141 chip->buffer = devm_kzalloc(&spi->dev, chip->registers, GFP_KERNEL); 142 if (!chip->buffer) 143 return -ENOMEM; 144 145 chip->gpio_chip.can_sleep = true; 146 chip->gpio_chip.dev = &spi->dev; 147 chip->gpio_chip.owner = THIS_MODULE; 148 149 mutex_init(&chip->lock); 150 151 ret = __gen_74x164_write_config(chip); 152 if (ret) { 153 dev_err(&spi->dev, "Failed writing: %d\n", ret); 154 goto exit_destroy; 155 } 156 157 ret = gpiochip_add(&chip->gpio_chip); 158 if (!ret) 159 return 0; 160 161 exit_destroy: 162 mutex_destroy(&chip->lock); 163 164 return ret; 165 } 166 167 static int gen_74x164_remove(struct spi_device *spi) 168 { 169 struct gen_74x164_chip *chip = spi_get_drvdata(spi); 170 171 gpiochip_remove(&chip->gpio_chip); 172 mutex_destroy(&chip->lock); 173 174 return 0; 175 } 176 177 static const struct of_device_id gen_74x164_dt_ids[] = { 178 { .compatible = "fairchild,74hc595" }, 179 {}, 180 }; 181 MODULE_DEVICE_TABLE(of, gen_74x164_dt_ids); 182 183 static struct spi_driver gen_74x164_driver = { 184 .driver = { 185 .name = "74x164", 186 .of_match_table = gen_74x164_dt_ids, 187 }, 188 .probe = gen_74x164_probe, 189 .remove = gen_74x164_remove, 190 }; 191 module_spi_driver(gen_74x164_driver); 192 193 MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>"); 194 MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>"); 195 MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register"); 196 MODULE_LICENSE("GPL v2"); 197