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/input-polldev.h> 21 #include <linux/kernel.h> 22 #include <linux/module.h> 23 #include <linux/of.h> 24 #include <linux/platform_device.h> 25 26 struct gpio_decoder { 27 struct input_polled_dev *poll_dev; 28 struct gpio_descs *input_gpios; 29 struct device *dev; 30 u32 axis; 31 u32 last_stable; 32 }; 33 34 static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder) 35 { 36 struct gpio_descs *gpios = decoder->input_gpios; 37 unsigned int ret = 0; 38 int i, val; 39 40 for (i = 0; i < gpios->ndescs; i++) { 41 val = gpiod_get_value_cansleep(gpios->desc[i]); 42 if (val < 0) { 43 dev_err(decoder->dev, 44 "Error reading gpio %d: %d\n", 45 desc_to_gpio(gpios->desc[i]), val); 46 return val; 47 } 48 49 val = !!val; 50 ret = (ret << 1) | val; 51 } 52 53 return ret; 54 } 55 56 static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev) 57 { 58 struct gpio_decoder *decoder = poll_dev->private; 59 int state; 60 61 state = gpio_decoder_get_gpios_state(decoder); 62 if (state >= 0 && state != decoder->last_stable) { 63 input_report_abs(poll_dev->input, decoder->axis, state); 64 input_sync(poll_dev->input); 65 decoder->last_stable = state; 66 } 67 } 68 69 static int gpio_decoder_probe(struct platform_device *pdev) 70 { 71 struct device *dev = &pdev->dev; 72 struct gpio_decoder *decoder; 73 struct input_polled_dev *poll_dev; 74 u32 max; 75 int err; 76 77 decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL); 78 if (!decoder) 79 return -ENOMEM; 80 81 device_property_read_u32(dev, "linux,axis", &decoder->axis); 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 if (decoder->input_gpios->ndescs < 2) { 88 dev_err(dev, "not enough gpios found\n"); 89 return -EINVAL; 90 } 91 92 if (device_property_read_u32(dev, "decoder-max-value", &max)) 93 max = (1U << decoder->input_gpios->ndescs) - 1; 94 95 decoder->dev = dev; 96 poll_dev = devm_input_allocate_polled_device(decoder->dev); 97 if (!poll_dev) 98 return -ENOMEM; 99 100 poll_dev->private = decoder; 101 poll_dev->poll = gpio_decoder_poll_gpios; 102 decoder->poll_dev = poll_dev; 103 104 poll_dev->input->name = pdev->name; 105 poll_dev->input->id.bustype = BUS_HOST; 106 input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 0); 107 108 err = input_register_polled_device(poll_dev); 109 if (err) { 110 dev_err(dev, "failed to register polled device\n"); 111 return err; 112 } 113 114 return 0; 115 } 116 117 #ifdef CONFIG_OF 118 static const struct of_device_id gpio_decoder_of_match[] = { 119 { .compatible = "gpio-decoder", }, 120 { }, 121 }; 122 MODULE_DEVICE_TABLE(of, gpio_decoder_of_match); 123 #endif 124 125 static struct platform_driver gpio_decoder_driver = { 126 .probe = gpio_decoder_probe, 127 .driver = { 128 .name = "gpio-decoder", 129 .of_match_table = of_match_ptr(gpio_decoder_of_match), 130 } 131 }; 132 module_platform_driver(gpio_decoder_driver); 133 134 MODULE_DESCRIPTION("GPIO decoder input driver"); 135 MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>"); 136 MODULE_LICENSE("GPL v2"); 137