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/mod_devicetable.h> 33 #include <linux/module.h> 34 #include <linux/mutex.h> 35 #include <linux/property.h> 36 #include <linux/spi/spi.h> 37 #include <uapi/linux/uleds.h> 38 39 struct spi_byte_chipdef { 40 /* SPI byte that will be send to switch the LED off */ 41 u8 off_value; 42 /* SPI byte that will be send to switch the LED to maximum brightness */ 43 u8 max_value; 44 }; 45 46 struct spi_byte_led { 47 struct led_classdev ldev; 48 struct spi_device *spi; 49 char name[LED_MAX_NAME_SIZE]; 50 struct mutex mutex; 51 const struct spi_byte_chipdef *cdef; 52 }; 53 54 static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = { 55 .off_value = 0x0, 56 .max_value = 0x3F, 57 }; 58 59 static int spi_byte_brightness_set_blocking(struct led_classdev *dev, 60 enum led_brightness brightness) 61 { 62 struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev); 63 u8 value; 64 int ret; 65 66 value = (u8) brightness + led->cdef->off_value; 67 68 mutex_lock(&led->mutex); 69 ret = spi_write(led->spi, &value, sizeof(value)); 70 mutex_unlock(&led->mutex); 71 72 return ret; 73 } 74 75 static int spi_byte_probe(struct spi_device *spi) 76 { 77 struct fwnode_handle *child __free(fwnode_handle) = NULL; 78 struct device *dev = &spi->dev; 79 struct spi_byte_led *led; 80 struct led_init_data init_data = {}; 81 enum led_default_state state; 82 int ret; 83 84 if (device_get_child_node_count(dev) != 1) { 85 dev_err(dev, "Device must have exactly one LED sub-node."); 86 return -EINVAL; 87 } 88 89 led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL); 90 if (!led) 91 return -ENOMEM; 92 93 ret = devm_mutex_init(dev, &led->mutex); 94 if (ret) 95 return ret; 96 97 led->spi = spi; 98 led->cdef = device_get_match_data(dev); 99 led->ldev.brightness = LED_OFF; 100 led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value; 101 led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking; 102 103 child = device_get_next_child_node(dev, NULL); 104 105 state = led_init_default_state_get(child); 106 if (state == LEDS_DEFSTATE_ON) 107 led->ldev.brightness = led->ldev.max_brightness; 108 spi_byte_brightness_set_blocking(&led->ldev, 109 led->ldev.brightness); 110 111 init_data.fwnode = child; 112 init_data.devicename = "leds-spi-byte"; 113 init_data.default_label = ":"; 114 115 return devm_led_classdev_register_ext(dev, &led->ldev, &init_data); 116 } 117 118 static const struct of_device_id spi_byte_dt_ids[] = { 119 { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef }, 120 {} 121 }; 122 MODULE_DEVICE_TABLE(of, spi_byte_dt_ids); 123 124 static struct spi_driver spi_byte_driver = { 125 .probe = spi_byte_probe, 126 .driver = { 127 .name = KBUILD_MODNAME, 128 .of_match_table = spi_byte_dt_ids, 129 }, 130 }; 131 module_spi_driver(spi_byte_driver); 132 133 MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>"); 134 MODULE_DESCRIPTION("single byte SPI LED driver"); 135 MODULE_LICENSE("GPL v2"); 136 MODULE_ALIAS("spi:leds-spi-byte"); 137