This series aims to add a led-backlight driver, similar to pwm-backlight,
but using a LED class device underneath.
A few years ago (2015), Tomi Valkeinen posted a series implementing a
backlight driver on top of a LED device:
https://patchwork.kernel.org/patch/7293991/
https://patchwork.kernel.org/patch/7294001/
https://patchwork.kernel.org/patch/7293981/
The discussion stopped because Tomi lacked the time to work on it.
changes in v5:
- removed LED brightness scaling
- disable sysfs the interface of the LEDs when used by the backlight device
changes in v4:
- fix dev_err() messages and commit logs following the advices of Pavel
- cosmetic changes (indents, getting rid of "? 1 : 0" in
led_match_led_node())
changes in v3:
- dt binding: don't limit the brightness range to 0-255. Use the range of
the underlying LEDs. as a side-effect, all LEDs must now have the same
range
- driver: Adapt to dt binding update.
- driver: rework probe() for clarity and remove the remaining goto.
changes in v2:
- handle more than one LED.
- don't make the backlight device a child of the LED controller.
- make brightness-levels and default-brightness-level optional
- removed the option to use a GPIO enable.
- removed the option to use a regulator. It should be handled by the LED
core
- don't make any change to the LED core (not needed anymore)
Jean-Jacques Hiblot (2):
leds: Add managed API to get a LED from a device driver
dt-bindings: backlight: Add led-backlight binding
Tomi Valkeinen (2):
leds: Add of_led_get() and led_put()
backlight: add led-backlight driver
.../bindings/leds/backlight/led-backlight.txt | 28 ++
drivers/leds/led-class.c | 92 ++++++
drivers/video/backlight/Kconfig | 7 +
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/led_bl.c | 264 ++++++++++++++++++
include/linux/leds.h | 6 +
6 files changed, 398 insertions(+)
create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
create mode 100644 drivers/video/backlight/led_bl.c
--
2.17.1
If the LED is acquired by a consumer device with devm_led_get(), it is
automatically released when the device is detached.
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
Acked-by: Pavel Machek <[email protected]>
---
drivers/leds/led-class.c | 42 ++++++++++++++++++++++++++++++++++++++++
include/linux/leds.h | 2 ++
2 files changed, 44 insertions(+)
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index eb98bf13e53b..7763aad8fabe 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -263,6 +263,48 @@ void led_put(struct led_classdev *led_cdev)
}
EXPORT_SYMBOL_GPL(led_put);
+static void devm_led_release(struct device *dev, void *res)
+{
+ struct led_classdev **p = res;
+
+ led_put(*p);
+}
+
+/**
+ * devm_led_get - Resource-managed request of a LED device
+ * @dev: LED consumer
+ * @idx: index of the LED to obtain in the consumer
+ *
+ * The device node of the device is parse to find the request LED device.
+ * The LED device returned from this function is automatically released
+ * on driver detach.
+ *
+ * @return a pointer to a LED device or ERR_PTR(errno) on failure.
+ */
+struct led_classdev *__must_check devm_led_get(struct device *dev,
+ int index)
+{
+ struct led_classdev *led;
+ struct led_classdev **dr;
+
+ led = of_led_get(dev->of_node, index);
+ if (IS_ERR(led))
+ return led;
+
+ dr = devres_alloc(devm_led_release, sizeof(struct led_classdev *),
+ GFP_KERNEL);
+ if (!dr) {
+ led_put(led);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ *dr = led;
+ devres_add(dev, dr);
+
+ return led;
+}
+EXPORT_SYMBOL_GPL(devm_led_get);
+
static int match_name(struct device *dev, const void *data)
{
if (!dev_name(dev))
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 0a71c7cdd191..7fcec566d774 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -148,6 +148,8 @@ extern void led_classdev_resume(struct led_classdev *led_cdev);
extern struct led_classdev *of_led_get(struct device_node *np, int index);
extern void led_put(struct led_classdev *led_cdev);
+struct led_classdev *__must_check devm_led_get(struct device *dev,
+ int index);
/**
* led_blink_set - set blinking with software fallback
--
2.17.1
From: Tomi Valkeinen <[email protected]>
This patch adds basic support for a kernel driver to get a LED device.
This will be used by the led-backlight driver.
Only OF version is implemented for now, and the behavior is similar to
PWM's of_pwm_get() and pwm_put().
Signed-off-by: Tomi Valkeinen <[email protected]>
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
Acked-by: Pavel Machek <[email protected]>
---
drivers/leds/led-class.c | 50 ++++++++++++++++++++++++++++++++++++++++
include/linux/leds.h | 4 ++++
2 files changed, 54 insertions(+)
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 4e2af8df5aa8..eb98bf13e53b 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -18,6 +18,7 @@
#include <linux/spinlock.h>
#include <linux/timer.h>
#include <uapi/linux/uleds.h>
+#include <linux/of.h>
#include "leds.h"
static struct class *leds_class;
@@ -213,6 +214,55 @@ static int led_resume(struct device *dev)
static SIMPLE_DEV_PM_OPS(leds_class_dev_pm_ops, led_suspend, led_resume);
+static int led_match_led_node(struct device *led_dev, const void *data)
+{
+ return led_dev->of_node == data;
+}
+
+/**
+ * of_led_get() - request a LED device via the LED framework
+ * @np: device node to get the LED device from
+ * @index: the index of the LED
+ *
+ * Returns the LED device parsed from the phandle specified in the "leds"
+ * property of a device tree node or a negative error-code on failure.
+ */
+struct led_classdev *of_led_get(struct device_node *np, int index)
+{
+ struct device *led_dev;
+ struct led_classdev *led_cdev;
+ struct device_node *led_node;
+
+ led_node = of_parse_phandle(np, "leds", index);
+ if (!led_node)
+ return ERR_PTR(-ENOENT);
+
+ led_dev = class_find_device(leds_class, NULL, led_node,
+ led_match_led_node);
+ of_node_put(led_node);
+
+ if (!led_dev)
+ return ERR_PTR(-EPROBE_DEFER);
+
+ led_cdev = dev_get_drvdata(led_dev);
+
+ if (!try_module_get(led_cdev->dev->parent->driver->owner))
+ return ERR_PTR(-ENODEV);
+
+ return led_cdev;
+}
+EXPORT_SYMBOL_GPL(of_led_get);
+
+/**
+ * led_put() - release a LED device
+ * @led_cdev: LED device
+ */
+void led_put(struct led_classdev *led_cdev)
+{
+ module_put(led_cdev->dev->parent->driver->owner);
+}
+EXPORT_SYMBOL_GPL(led_put);
+
static int match_name(struct device *dev, const void *data)
{
if (!dev_name(dev))
diff --git a/include/linux/leds.h b/include/linux/leds.h
index bee8e3f8dddd..0a71c7cdd191 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -19,6 +19,7 @@
struct device;
struct led_pattern;
+struct device_node;
/*
* LED Core
*/
@@ -145,6 +146,9 @@ extern void devm_led_classdev_unregister(struct device *parent,
extern void led_classdev_suspend(struct led_classdev *led_cdev);
extern void led_classdev_resume(struct led_classdev *led_cdev);
+extern struct led_classdev *of_led_get(struct device_node *np, int index);
+extern void led_put(struct led_classdev *led_cdev);
+
/**
* led_blink_set - set blinking with software fallback
* @led_cdev: the LED to start blinking
--
2.17.1
Add DT binding for led-backlight.
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
---
.../bindings/leds/backlight/led-backlight.txt | 28 +++++++++++++++++++
1 file changed, 28 insertions(+)
create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
diff --git a/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
new file mode 100644
index 000000000000..4c7dfbe7f67a
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
@@ -0,0 +1,28 @@
+led-backlight bindings
+
+This binding is used to describe a basic backlight device made of LEDs.
+It can also be used to describe a backlight device controlled by the output of
+a LED driver.
+
+Required properties:
+ - compatible: "led-backlight"
+ - leds: a list of LEDs
+
+Optional properties:
+ - brightness-levels: Array of distinct brightness levels. The levels must be
+ in the range accepted by the underlying LED devices.
+ This is used to translate a backlight brightness level
+ into a LED brightness level. If it is not provided, the
+ identity mapping is used.
+
+ - default-brightness-level: The default brightness level.
+
+Example:
+
+ backlight {
+ compatible = "led-backlight";
+
+ leds = <&led1>, <&led2>;
+ brightness-levels = <0 4 8 16 32 64 128 255>;
+ default-brightness-level = <6>;
+ };
--
2.17.1