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(led->spi, &value, sizeof(value));
76	mutex_unlock(&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(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(dev_of_node(dev), NULL);
95
96	led = devm_kzalloc(dev, 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(child, "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(&led->ldev,
118					 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(&spi->dev, &led->ldev, &init_data);
125	if (ret) {
126		mutex_destroy(&led->mutex);
127		return ret;
128	}
129	spi_set_drvdata(spi, 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(&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