1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de> 3 4 /* 5 * The driver supports controllers with a very simple SPI protocol: 6 * - one LED is controlled by a single byte on MOSI 7 * - the value of the byte gives the brightness between two values (lowest to 8 * highest) 9 * - no return value is necessary (no MISO signal) 10 * 11 * The value for minimum and maximum brightness depends on the device 12 * (compatible string). 13 * 14 * Supported devices: 15 * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used 16 * for example in Ubiquiti airCube ISP. Reverse engineered protocol for this 17 * controller: 18 * * Higher two bits set a mode. Lower six bits are a parameter. 19 * * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max) 20 * * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From 21 * some tests, the period is about (50ms + 102ms * parameter). There is a 22 * slightly different pattern starting from 0x10 (longer gap between the 23 * pulses) but the time still follows that calculation. 24 * * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a 25 * slight jump in the pattern at 0x10. 26 * * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of 27 * (105ms * parameter) 28 * NOTE: This driver currently only supports mode 00. 29 */ 30 31 #include <linux/leds.h> 32 #include <linux/module.h> 33 #include <linux/of_device.h> 34 #include <linux/spi/spi.h> 35 #include <linux/mutex.h> 36 #include <uapi/linux/uleds.h> 37 38 struct spi_byte_chipdef { 39 /* SPI byte that will be send to switch the LED off */ 40 u8 off_value; 41 /* SPI byte that will be send to switch the LED to maximum brightness */ 42 u8 max_value; 43 }; 44 45 struct spi_byte_led { 46 struct led_classdev ldev; 47 struct spi_device *spi; 48 char name[LED_MAX_NAME_SIZE]; 49 struct mutex mutex; 50 const struct spi_byte_chipdef *cdef; 51 }; 52 53 static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = { 54 .off_value = 0x0, 55 .max_value = 0x3F, 56 }; 57 58 static const struct of_device_id spi_byte_dt_ids[] = { 59 { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef }, 60 {}, 61 }; 62 63 MODULE_DEVICE_TABLE(of, spi_byte_dt_ids); 64 65 static int spi_byte_brightness_set_blocking(struct led_classdev *dev, 66 enum led_brightness brightness) 67 { 68 struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev); 69 u8 value; 70 int ret; 71 72 value = (u8) brightness + led->cdef->off_value; 73 74 mutex_lock(&led->mutex); 75 ret = spi_write(led->spi, &value, sizeof(value)); 76 mutex_unlock(&led->mutex); 77 78 return ret; 79 } 80 81 static int spi_byte_probe(struct spi_device *spi) 82 { 83 struct device_node *child; 84 struct device *dev = &spi->dev; 85 struct spi_byte_led *led; 86 const char *name = "leds-spi-byte::"; 87 const char *state; 88 int ret; 89 90 if (of_get_available_child_count(dev_of_node(dev)) != 1) { 91 dev_err(dev, "Device must have exactly one LED sub-node."); 92 return -EINVAL; 93 } 94 child = of_get_next_available_child(dev_of_node(dev), NULL); 95 96 led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL); 97 if (!led) 98 return -ENOMEM; 99 100 of_property_read_string(child, "label", &name); 101 strlcpy(led->name, name, sizeof(led->name)); 102 led->spi = spi; 103 mutex_init(&led->mutex); 104 led->cdef = device_get_match_data(dev); 105 led->ldev.name = led->name; 106 led->ldev.brightness = LED_OFF; 107 led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value; 108 led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking; 109 110 state = of_get_property(child, "default-state", NULL); 111 if (state) { 112 if (!strcmp(state, "on")) { 113 led->ldev.brightness = led->ldev.max_brightness; 114 } else if (strcmp(state, "off")) { 115 /* all other cases except "off" */ 116 dev_err(dev, "default-state can only be 'on' or 'off'"); 117 return -EINVAL; 118 } 119 } 120 spi_byte_brightness_set_blocking(&led->ldev, 121 led->ldev.brightness); 122 123 ret = devm_led_classdev_register(&spi->dev, &led->ldev); 124 if (ret) { 125 mutex_destroy(&led->mutex); 126 return ret; 127 } 128 spi_set_drvdata(spi, led); 129 130 return 0; 131 } 132 133 static void spi_byte_remove(struct spi_device *spi) 134 { 135 struct spi_byte_led *led = spi_get_drvdata(spi); 136 137 mutex_destroy(&led->mutex); 138 } 139 140 static struct spi_driver spi_byte_driver = { 141 .probe = spi_byte_probe, 142 .remove = spi_byte_remove, 143 .driver = { 144 .name = KBUILD_MODNAME, 145 .of_match_table = spi_byte_dt_ids, 146 }, 147 }; 148 149 module_spi_driver(spi_byte_driver); 150 151 MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>"); 152 MODULE_DESCRIPTION("single byte SPI LED driver"); 153 MODULE_LICENSE("GPL v2"); 154 MODULE_ALIAS("spi:leds-spi-byte"); 155