diff options
Diffstat (limited to 'drivers/leds/leds-spi-byte.c')
| -rw-r--r-- | drivers/leds/leds-spi-byte.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/drivers/leds/leds-spi-byte.c b/drivers/leds/leds-spi-byte.c new file mode 100644 index 000000000..2bc5c99da --- /dev/null +++ b/drivers/leds/leds-spi-byte.c @@ -0,0 +1,154 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de> + +/* + * 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/module.h> +#include <linux/of_device.h> +#include <linux/spi/spi.h> +#include <linux/mutex.h> +#include <uapi/linux/uleds.h> + +struct spi_byte_chipdef { + /* SPI byte that will be send to switch the LED off */ + u8 off_value; + /* SPI byte that will be send to switch the LED to maximum brightness */ + u8 max_value; +}; + +struct spi_byte_led { + struct led_classdev ldev; + struct spi_device *spi; + char name[LED_MAX_NAME_SIZE]; + struct mutex mutex; + const struct spi_byte_chipdef *cdef; +}; + +static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = { + .off_value = 0x0, + .max_value = 0x3F, +}; + +static const struct of_device_id spi_byte_dt_ids[] = { + { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef }, + {}, +}; + +MODULE_DEVICE_TABLE(of, spi_byte_dt_ids); + +static int spi_byte_brightness_set_blocking(struct led_classdev *dev, + enum led_brightness brightness) +{ + struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev); + u8 value; + int ret; + + value = (u8) brightness + led->cdef->off_value; + + mutex_lock(&led->mutex); + ret = spi_write(led->spi, &value, sizeof(value)); + mutex_unlock(&led->mutex); + + return ret; +} + +static int spi_byte_probe(struct spi_device *spi) +{ + struct device_node *child; + struct device *dev = &spi->dev; + struct spi_byte_led *led; + const char *name = "leds-spi-byte::"; + const char *state; + int ret; + + if (of_get_available_child_count(dev_of_node(dev)) != 1) { + dev_err(dev, "Device must have exactly one LED sub-node."); + return -EINVAL; + } + child = of_get_next_available_child(dev_of_node(dev), NULL); + + led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL); + if (!led) + return -ENOMEM; + + of_property_read_string(child, "label", &name); + strlcpy(led->name, name, sizeof(led->name)); + led->spi = spi; + mutex_init(&led->mutex); + led->cdef = device_get_match_data(dev); + led->ldev.name = led->name; + led->ldev.brightness = LED_OFF; + led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value; + led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking; + + state = of_get_property(child, "default-state", NULL); + if (state) { + if (!strcmp(state, "on")) { + led->ldev.brightness = led->ldev.max_brightness; + } else if (strcmp(state, "off")) { + /* all other cases except "off" */ + dev_err(dev, "default-state can only be 'on' or 'off'"); + return -EINVAL; + } + } + spi_byte_brightness_set_blocking(&led->ldev, + led->ldev.brightness); + + ret = devm_led_classdev_register(&spi->dev, &led->ldev); + if (ret) { + mutex_destroy(&led->mutex); + return ret; + } + spi_set_drvdata(spi, led); + + return 0; +} + +static void spi_byte_remove(struct spi_device *spi) +{ + struct spi_byte_led *led = spi_get_drvdata(spi); + + mutex_destroy(&led->mutex); +} + +static struct spi_driver spi_byte_driver = { + .probe = spi_byte_probe, + .remove = spi_byte_remove, + .driver = { + .name = KBUILD_MODNAME, + .of_match_table = spi_byte_dt_ids, + }, +}; + +module_spi_driver(spi_byte_driver); + +MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>"); +MODULE_DESCRIPTION("single byte SPI LED driver"); +MODULE_LICENSE("GPL v2"); +MODULE_ALIAS("spi:leds-spi-byte"); |