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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 | { | |
e9a804d7 CM |
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 | ||
99a013c8 | 90 | if (of_get_available_child_count(dev_of_node(dev)) != 1) { |
e9a804d7 CM |
91 | dev_err(dev, "Device must have exactly one LED sub-node."); |
92 | return -EINVAL; | |
93 | } | |
99a013c8 | 94 | child = of_get_next_available_child(dev_of_node(dev), NULL); |
e9a804d7 CM |
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); | |
2779f472 | 104 | led->cdef = device_get_match_data(dev); |
e9a804d7 CM |
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 int 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 | return 0; | |
140 | } | |
141 | ||
142 | static struct spi_driver spi_byte_driver = { | |
143 | .probe = spi_byte_probe, | |
144 | .remove = spi_byte_remove, | |
145 | .driver = { | |
146 | .name = KBUILD_MODNAME, | |
147 | .of_match_table = spi_byte_dt_ids, | |
148 | }, | |
149 | }; | |
150 | ||
151 | module_spi_driver(spi_byte_driver); | |
152 | ||
153 | MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>"); | |
154 | MODULE_DESCRIPTION("single byte SPI LED driver"); | |
155 | MODULE_LICENSE("GPL v2"); | |
156 | MODULE_ALIAS("spi:leds-spi-byte"); |