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.h>
34#include <linux/spi/spi.h>
35#include <linux/mutex.h>
36#include <uapi/linux/uleds.h>
37
38struct 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
45struct 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
53static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {
54 .off_value = 0x0,
55 .max_value = 0x3F,
56};
57
58static const struct of_device_id spi_byte_dt_ids[] = {
59 { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },
60 {},
61};
62
63MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);
64
65static 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(spi: led->spi, buf: &value, len: sizeof(value));
76 mutex_unlock(lock: &led->mutex);
77
78 return ret;
79}
80
81static 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 struct led_init_data init_data = {};
87 const char *state;
88 int ret;
89
90 if (of_get_available_child_count(np: 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(node: dev_of_node(dev), NULL);
95
96 led = devm_kzalloc(dev, size: sizeof(*led), GFP_KERNEL);
97 if (!led)
98 return -ENOMEM;
99
100 led->spi = spi;
101 mutex_init(&led->mutex);
102 led->cdef = device_get_match_data(dev);
103 led->ldev.brightness = LED_OFF;
104 led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
105 led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
106
107 state = of_get_property(node: child, name: "default-state", NULL);
108 if (state) {
109 if (!strcmp(state, "on")) {
110 led->ldev.brightness = led->ldev.max_brightness;
111 } else if (strcmp(state, "off")) {
112 /* all other cases except "off" */
113 dev_err(dev, "default-state can only be 'on' or 'off'");
114 return -EINVAL;
115 }
116 }
117 spi_byte_brightness_set_blocking(dev: &led->ldev,
118 brightness: led->ldev.brightness);
119
120 init_data.fwnode = of_fwnode_handle(child);
121 init_data.devicename = "leds-spi-byte";
122 init_data.default_label = ":";
123
124 ret = devm_led_classdev_register_ext(parent: &spi->dev, led_cdev: &led->ldev, init_data: &init_data);
125 if (ret) {
126 mutex_destroy(lock: &led->mutex);
127 return ret;
128 }
129 spi_set_drvdata(spi, data: led);
130
131 return 0;
132}
133
134static void spi_byte_remove(struct spi_device *spi)
135{
136 struct spi_byte_led *led = spi_get_drvdata(spi);
137
138 mutex_destroy(lock: &led->mutex);
139}
140
141static struct spi_driver spi_byte_driver = {
142 .probe = spi_byte_probe,
143 .remove = spi_byte_remove,
144 .driver = {
145 .name = KBUILD_MODNAME,
146 .of_match_table = spi_byte_dt_ids,
147 },
148};
149
150module_spi_driver(spi_byte_driver);
151
152MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
153MODULE_DESCRIPTION("single byte SPI LED driver");
154MODULE_LICENSE("GPL v2");
155MODULE_ALIAS("spi:leds-spi-byte");
156

source code of linux/drivers/leds/leds-spi-byte.c