1 /* 2 * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/ 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License as 6 * published by the Free Software Foundation version 2. 7 * 8 * This program is distributed "as is" WITHOUT ANY WARRANTY of any 9 * kind, whether express or implied; without even the implied warranty 10 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 * GNU General Public License for more details. 12 * 13 * A generic driver to read multiple gpio lines and translate the 14 * encoded numeric value into an input event. 15 */ 16 17 #include <linux/device.h> 18 #include <linux/gpio/consumer.h> 19 #include <linux/input.h> 20 #include <linux/kernel.h> 21 #include <linux/module.h> 22 #include <linux/of.h> 23 #include <linux/platform_device.h> 24 25 struct gpio_decoder { 26 struct gpio_descs *input_gpios; 27 struct device *dev; 28 u32 axis; 29 u32 last_stable; 30 }; 31 32 static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder) 33 { 34 struct gpio_descs *gpios = decoder->input_gpios; 35 unsigned int ret = 0; 36 int i, val; 37 38 for (i = 0; i < gpios->ndescs; i++) { 39 val = gpiod_get_value_cansleep(gpios->desc[i]); 40 if (val < 0) { 41 dev_err(decoder->dev, 42 "Error reading gpio %d: %d\n", 43 desc_to_gpio(gpios->desc[i]), val); 44 return val; 45 } 46 47 val = !!val; 48 ret = (ret << 1) | val; 49 } 50 51 return ret; 52 } 53 54 static void gpio_decoder_poll_gpios(struct input_dev *input) 55 { 56 struct gpio_decoder *decoder = input_get_drvdata(input); 57 int state; 58 59 state = gpio_decoder_get_gpios_state(decoder); 60 if (state >= 0 && state != decoder->last_stable) { 61 input_report_abs(input, decoder->axis, state); 62 input_sync(input); 63 decoder->last_stable = state; 64 } 65 } 66 67 static int gpio_decoder_probe(struct platform_device *pdev) 68 { 69 struct device *dev = &pdev->dev; 70 struct gpio_decoder *decoder; 71 struct input_dev *input; 72 u32 max; 73 int err; 74 75 decoder = devm_kzalloc(dev, sizeof(*decoder), GFP_KERNEL); 76 if (!decoder) 77 return -ENOMEM; 78 79 decoder->dev = dev; 80 device_property_read_u32(dev, "linux,axis", &decoder->axis); 81 82 decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN); 83 if (IS_ERR(decoder->input_gpios)) { 84 dev_err(dev, "unable to acquire input gpios\n"); 85 return PTR_ERR(decoder->input_gpios); 86 } 87 88 if (decoder->input_gpios->ndescs < 2) { 89 dev_err(dev, "not enough gpios found\n"); 90 return -EINVAL; 91 } 92 93 if (device_property_read_u32(dev, "decoder-max-value", &max)) 94 max = (1U << decoder->input_gpios->ndescs) - 1; 95 96 input = devm_input_allocate_device(dev); 97 if (!input) 98 return -ENOMEM; 99 100 input_set_drvdata(input, decoder); 101 102 input->name = pdev->name; 103 input->id.bustype = BUS_HOST; 104 input_set_abs_params(input, decoder->axis, 0, max, 0, 0); 105 106 err = input_setup_polling(input, gpio_decoder_poll_gpios); 107 if (err) { 108 dev_err(dev, "failed to set up polling\n"); 109 return err; 110 } 111 112 err = input_register_device(input); 113 if (err) { 114 dev_err(dev, "failed to register input device\n"); 115 return err; 116 } 117 118 return 0; 119 } 120 121 #ifdef CONFIG_OF 122 static const struct of_device_id gpio_decoder_of_match[] = { 123 { .compatible = "gpio-decoder", }, 124 { }, 125 }; 126 MODULE_DEVICE_TABLE(of, gpio_decoder_of_match); 127 #endif 128 129 static struct platform_driver gpio_decoder_driver = { 130 .probe = gpio_decoder_probe, 131 .driver = { 132 .name = "gpio-decoder", 133 .of_match_table = of_match_ptr(gpio_decoder_of_match), 134 } 135 }; 136 module_platform_driver(gpio_decoder_driver); 137 138 MODULE_DESCRIPTION("GPIO decoder input driver"); 139 MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>"); 140 MODULE_LICENSE("GPL v2"); 141