linux/drivers/leds/leds-spi-byte.c

// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Christian Mauderer <[email protected]>

/*
 * The driver supports controllers with a very simple SPI protocol:
 * - one LED is controlled by a single byte on MOSI
 * - the value of the byte gives the brightness between two values (lowest to
 *   highest)
 * - no return value is necessary (no MISO signal)
 *
 * The value for minimum and maximum brightness depends on the device
 * (compatible string).
 *
 * Supported devices:
 * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used
 *   for example in Ubiquiti airCube ISP. Reverse engineered protocol for this
 *   controller:
 *   * Higher two bits set a mode. Lower six bits are a parameter.
 *   * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max)
 *   * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From
 *     some tests, the period is about (50ms + 102ms * parameter). There is a
 *     slightly different pattern starting from 0x10 (longer gap between the
 *     pulses) but the time still follows that calculation.
 *   * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a
 *     slight jump in the pattern at 0x10.
 *   * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of
 *     (105ms * parameter)
 *   NOTE: This driver currently only supports mode 00.
 */

#include <linux/leds.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/spi/spi.h>
#include <uapi/linux/uleds.h>

struct spi_byte_chipdef { … };

struct spi_byte_led { … };

static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = …;

static int spi_byte_brightness_set_blocking(struct led_classdev *dev,
					    enum led_brightness brightness)
{ … }

static int spi_byte_probe(struct spi_device *spi)
{ … }

static const struct of_device_id spi_byte_dt_ids[] = …;
MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);

static struct spi_driver spi_byte_driver = …;
module_spi_driver(…) …;

MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;
MODULE_ALIAS(…) …;