155 lines
4.4 KiB
C
155 lines
4.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de>
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/*
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* The driver supports controllers with a very simple SPI protocol:
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* - one LED is controlled by a single byte on MOSI
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* - the value of the byte gives the brightness between two values (lowest to
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* highest)
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* - no return value is necessary (no MISO signal)
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*
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* The value for minimum and maximum brightness depends on the device
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* (compatible string).
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*
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* Supported devices:
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* - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used
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* for example in Ubiquiti airCube ISP. Reverse engineered protocol for this
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* controller:
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* * Higher two bits set a mode. Lower six bits are a parameter.
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* * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max)
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* * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From
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* some tests, the period is about (50ms + 102ms * parameter). There is a
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* slightly different pattern starting from 0x10 (longer gap between the
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* pulses) but the time still follows that calculation.
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* * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a
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* slight jump in the pattern at 0x10.
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* * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of
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* (105ms * parameter)
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* NOTE: This driver currently only supports mode 00.
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*/
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#include <linux/leds.h>
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#include <linux/module.h>
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#include <linux/of_device.h>
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#include <linux/spi/spi.h>
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#include <linux/mutex.h>
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#include <uapi/linux/uleds.h>
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struct spi_byte_chipdef {
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/* SPI byte that will be send to switch the LED off */
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u8 off_value;
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/* SPI byte that will be send to switch the LED to maximum brightness */
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u8 max_value;
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};
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struct spi_byte_led {
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struct led_classdev ldev;
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struct spi_device *spi;
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char name[LED_MAX_NAME_SIZE];
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struct mutex mutex;
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const struct spi_byte_chipdef *cdef;
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};
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static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {
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.off_value = 0x0,
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.max_value = 0x3F,
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};
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static const struct of_device_id spi_byte_dt_ids[] = {
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{ .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },
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{},
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};
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MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);
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static int spi_byte_brightness_set_blocking(struct led_classdev *dev,
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enum led_brightness brightness)
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{
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struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev);
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u8 value;
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int ret;
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value = (u8) brightness + led->cdef->off_value;
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mutex_lock(&led->mutex);
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ret = spi_write(led->spi, &value, sizeof(value));
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mutex_unlock(&led->mutex);
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return ret;
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}
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static int spi_byte_probe(struct spi_device *spi)
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{
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struct device_node *child;
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struct device *dev = &spi->dev;
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struct spi_byte_led *led;
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const char *name = "leds-spi-byte::";
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const char *state;
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int ret;
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if (of_get_available_child_count(dev_of_node(dev)) != 1) {
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dev_err(dev, "Device must have exactly one LED sub-node.");
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return -EINVAL;
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}
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child = of_get_next_available_child(dev_of_node(dev), NULL);
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led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
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if (!led)
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return -ENOMEM;
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of_property_read_string(child, "label", &name);
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strlcpy(led->name, name, sizeof(led->name));
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led->spi = spi;
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mutex_init(&led->mutex);
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led->cdef = device_get_match_data(dev);
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led->ldev.name = led->name;
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led->ldev.brightness = LED_OFF;
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led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
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led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
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state = of_get_property(child, "default-state", NULL);
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if (state) {
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if (!strcmp(state, "on")) {
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led->ldev.brightness = led->ldev.max_brightness;
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} else if (strcmp(state, "off")) {
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/* all other cases except "off" */
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dev_err(dev, "default-state can only be 'on' or 'off'");
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return -EINVAL;
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}
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}
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spi_byte_brightness_set_blocking(&led->ldev,
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led->ldev.brightness);
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ret = devm_led_classdev_register(&spi->dev, &led->ldev);
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if (ret) {
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mutex_destroy(&led->mutex);
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return ret;
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}
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spi_set_drvdata(spi, led);
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return 0;
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}
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static void spi_byte_remove(struct spi_device *spi)
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{
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struct spi_byte_led *led = spi_get_drvdata(spi);
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mutex_destroy(&led->mutex);
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}
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static struct spi_driver spi_byte_driver = {
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.probe = spi_byte_probe,
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.remove = spi_byte_remove,
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.driver = {
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.name = KBUILD_MODNAME,
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.of_match_table = spi_byte_dt_ids,
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},
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};
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module_spi_driver(spi_byte_driver);
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MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
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MODULE_DESCRIPTION("single byte SPI LED driver");
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MODULE_LICENSE("GPL v2");
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MODULE_ALIAS("spi:leds-spi-byte");
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