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
spi_byte_brightness_set_blocking(struct led_classdev * dev,enum led_brightness brightness)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
spi_byte_probe(struct spi_device * spi)81 static int spi_byte_probe(struct spi_device *spi)
82 {
83 const struct of_device_id *of_dev_id;
84 struct device_node *child;
85 struct device *dev = &spi->dev;
86 struct spi_byte_led *led;
87 const char *name = "leds-spi-byte::";
88 const char *state;
89 int ret;
90
91 of_dev_id = of_match_device(spi_byte_dt_ids, dev);
92 if (!of_dev_id)
93 return -EINVAL;
94
95 if (of_get_child_count(dev->of_node) != 1) {
96 dev_err(dev, "Device must have exactly one LED sub-node.");
97 return -EINVAL;
98 }
99 child = of_get_next_child(dev->of_node, NULL);
100
101 led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
102 if (!led)
103 return -ENOMEM;
104
105 of_property_read_string(child, "label", &name);
106 strlcpy(led->name, name, sizeof(led->name));
107 led->spi = spi;
108 mutex_init(&led->mutex);
109 led->cdef = of_dev_id->data;
110 led->ldev.name = led->name;
111 led->ldev.brightness = LED_OFF;
112 led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
113 led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
114
115 state = of_get_property(child, "default-state", NULL);
116 if (state) {
117 if (!strcmp(state, "on")) {
118 led->ldev.brightness = led->ldev.max_brightness;
119 } else if (strcmp(state, "off")) {
120 /* all other cases except "off" */
121 dev_err(dev, "default-state can only be 'on' or 'off'");
122 return -EINVAL;
123 }
124 }
125 spi_byte_brightness_set_blocking(&led->ldev,
126 led->ldev.brightness);
127
128 ret = devm_led_classdev_register(&spi->dev, &led->ldev);
129 if (ret) {
130 mutex_destroy(&led->mutex);
131 return ret;
132 }
133 spi_set_drvdata(spi, led);
134
135 return 0;
136 }
137
spi_byte_remove(struct spi_device * spi)138 static int spi_byte_remove(struct spi_device *spi)
139 {
140 struct spi_byte_led *led = spi_get_drvdata(spi);
141
142 mutex_destroy(&led->mutex);
143
144 return 0;
145 }
146
147 static struct spi_driver spi_byte_driver = {
148 .probe = spi_byte_probe,
149 .remove = spi_byte_remove,
150 .driver = {
151 .name = KBUILD_MODNAME,
152 .of_match_table = spi_byte_dt_ids,
153 },
154 };
155
156 module_spi_driver(spi_byte_driver);
157
158 MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
159 MODULE_DESCRIPTION("single byte SPI LED driver");
160 MODULE_LICENSE("GPL v2");
161 MODULE_ALIAS("spi:leds-spi-byte");
162