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
spi_byte_brightness_set_blocking(struct led_classdev * dev,enum led_brightness brightness)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
spi_byte_probe(struct spi_device * spi)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