cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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leds-spi-byte.c (4527B)

      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
     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	const char *name = "leds-spi-byte::";
     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	of_property_read_string(child, "label", &name);
    101	strlcpy(led->name, name, sizeof(led->name));
    102	led->spi = spi;
    103	mutex_init(&led->mutex);
    104	led->cdef = device_get_match_data(dev);
    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
    133static void 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
    140static struct spi_driver spi_byte_driver = {
    141	.probe		= spi_byte_probe,
    142	.remove		= spi_byte_remove,
    143	.driver = {
    144		.name		= KBUILD_MODNAME,
    145		.of_match_table	= spi_byte_dt_ids,
    146	},
    147};
    148
    149module_spi_driver(spi_byte_driver);
    150
    151MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
    152MODULE_DESCRIPTION("single byte SPI LED driver");
    153MODULE_LICENSE("GPL v2");
    154MODULE_ALIAS("spi:leds-spi-byte");