From: Christian Mauderer <oss@xxxxxxxxxxxxx>
This driver adds support for simple SPI based LED controller which use
only one byte for setting the brightness.
Signed-off-by: Christian Mauderer <oss@xxxxxxxxxxxxx>
---
Changes compared to v3:
- remove led_classdev_unregister - not longer necessary due to
devm_led_classdev_register
- move off_value and max_value to chipdef structure
- reduce intermediate local variables during open firmware parsing
- destroy mutex if devm_led_classdev_register went wrong
- add 'default-state'
Changes compared to v2:
- use "if (ret)" instead of "if (ret != 0)"
- don't initialize ldev-fields with zero
- use devm_led_classdev_register instead of led_classdev_register
- check for error instead of good case with the last if in spi_byte_probe
Changes compared to v1:
- rename ubnt-spi to leds-spi-byte
- rework probe to get all parameters before allocating anything -> error checks
all collected together and initializing all fields of the device structure is
more obvious
- fix some unsteady indentations during variable declaration
- rework comment with protocol explanation
- handle case of off_bright > max_bright
- fix spelling in commit message
- mutex_destroy in remove
- change label to use either use the given one without a prefix or a default one
drivers/leds/Kconfig | 10 +++
drivers/leds/Makefile | 1 +
drivers/leds/leds-spi-byte.c | 161 +++++++++++++++++++++++++++++++++++
3 files changed, 172 insertions(+)
create mode 100644 drivers/leds/leds-spi-byte.c
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index a72f97fca57b..b6235e7e1482 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -766,6 +766,16 @@ config LEDS_NIC78BX
To compile this driver as a module, choose M here: the module
will be called leds-nic78bx.
+config LEDS_SPI_BYTE
+ tristate "LED support for SPI LED controller with a single byte"
+ depends on LEDS_CLASS
+ depends on SPI
+ depends on OF
+ help
+ This option enables support for LED controller which use a single byte
+ for controlling the brightness. Currently the following controller is
+ supported: Ubiquiti airCube ISP microcontroller based LED controller.
+
comment "LED Triggers"
source "drivers/leds/trigger/Kconfig"
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 4c1b0054f379..1786d7e2c236 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -75,6 +75,7 @@ obj-$(CONFIG_LEDS_PM8058) += leds-pm8058.o
obj-$(CONFIG_LEDS_MLXCPLD) += leds-mlxcpld.o
obj-$(CONFIG_LEDS_MLXREG) += leds-mlxreg.o
obj-$(CONFIG_LEDS_NIC78BX) += leds-nic78bx.o
+obj-$(CONFIG_LEDS_SPI_BYTE) += leds-spi-byte.o
obj-$(CONFIG_LEDS_MT6323) += leds-mt6323.o
obj-$(CONFIG_LEDS_LM3692X) += leds-lm3692x.o
obj-$(CONFIG_LEDS_SC27XX_BLTC) += leds-sc27xx-bltc.o
diff --git a/drivers/leds/leds-spi-byte.c b/drivers/leds/leds-spi-byte.c
new file mode 100644
index 000000000000..b231b563b7bb
--- /dev/null
+++ b/drivers/leds/leds-spi-byte.c
@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Christian Mauderer <oss@xxxxxxxxxxxxx>
+
+/*
+ * 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)
+{
+ const struct of_device_id *of_dev_id;
+ 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;
+
+ of_dev_id = of_match_device(spi_byte_dt_ids, dev);
+ if (!of_dev_id)
+ return -EINVAL;
+
+ if (of_get_child_count(dev->of_node) != 1) {
+ dev_err(dev, "Device must have exactly one LED sub-node.");
+ return -EINVAL;
+ }
+ child = of_get_next_child(dev->of_node, 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 = of_dev_id->data;
+ 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 int spi_byte_remove(struct spi_device *spi)
+{
+ struct spi_byte_led *led = spi_get_drvdata(spi);
+
+ mutex_destroy(&led->mutex);
+
+ return 0;
+}
+
+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@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("single byte SPI LED driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("spi:leds-spi-byte");
--
2.21.0
