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.
The series affects the LED core and add a new backlight driver.
changes in v2:
- bkl: the backlight can use more than one LED. As a consequence don't make
the backlight device a child of a LED controller.
- bkl: make brightness-levels and default-brightness-level optional
- bkl: removed the option to use a GPIO enable.
- bkl: removed the option to use a regulator. It should be handled by the
LED core
- led: removed the mechanism to bind a child device for each LED
- led: improve the way of_get_led() works and add a managed version of it
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 | 29 +++
drivers/leds/led-class.c | 92 +++++++
drivers/video/backlight/Kconfig | 7 +
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/led_bl.c | 235 ++++++++++++++++++
include/linux/leds.h | 6 +
6 files changed, 370 insertions(+)
create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
create mode 100644 drivers/video/backlight/led_bl.c
--
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]>
---
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 e01b2d982564..0f67b13b0f1f 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -19,6 +19,7 @@
#include <linux/timer.h>
#include <linux/regulator/consumer.h>
#include <uapi/linux/uleds.h>
+#include <linux/of.h>
#include "leds.h"
static struct class *leds_class;
@@ -214,6 +215,55 @@ 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 ? 1 : 0;
+}
+
+/**
+ * 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
From: Tomi Valkeinen <[email protected]>
This patch adds a led-backlight driver (led_bl), which is similar to
pwm_bl except the driver uses a LED class driver to adjust the
brightness in the HW. Multiple LEDs can be used for a single backlight.
Signed-off-by: Tomi Valkeinen <[email protected]>
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
---
drivers/video/backlight/Kconfig | 7 +
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/led_bl.c | 235 +++++++++++++++++++++++++++++++
3 files changed, 243 insertions(+)
create mode 100644 drivers/video/backlight/led_bl.c
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 8b081d61773e..585a1787618c 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -458,6 +458,13 @@ config BACKLIGHT_RAVE_SP
help
Support for backlight control on RAVE SP device.
+config BACKLIGHT_LED
+ tristate "Generic LED based Backlight Driver"
+ depends on LEDS_CLASS && OF
+ help
+ If you have a LCD backlight adjustable by LED class driver, say Y
+ to enable this driver.
+
endif # BACKLIGHT_CLASS_DEVICE
endmenu
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 63c507c07437..2a67642966a5 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -57,3 +57,4 @@ obj-$(CONFIG_BACKLIGHT_TPS65217) += tps65217_bl.o
obj-$(CONFIG_BACKLIGHT_WM831X) += wm831x_bl.o
obj-$(CONFIG_BACKLIGHT_ARCXCNN) += arcxcnn_bl.o
obj-$(CONFIG_BACKLIGHT_RAVE_SP) += rave-sp-backlight.o
+obj-$(CONFIG_BACKLIGHT_LED) += led_bl.o
diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
new file mode 100644
index 000000000000..7644277cfdbb
--- /dev/null
+++ b/drivers/video/backlight/led_bl.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Texas Instruments Incorporated - http://www.ti.com/
+ * Author: Tomi Valkeinen <[email protected]>
+ *
+ * Based on pwm_bl.c
+ */
+
+#include <linux/backlight.h>
+#include <linux/gpio/consumer.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define BKL_FULL_BRIGHTNESS 255
+
+struct led_bl_data {
+ struct device *dev;
+ struct backlight_device *bl_dev;
+ struct led_classdev **leds;
+ bool enabled;
+ int nb_leds;
+ unsigned int *levels;
+ unsigned int default_brightness;
+ unsigned int max_brightness;
+};
+
+static int to_led_brightness(struct led_classdev *led, int value)
+{
+ return (value * led->max_brightness) / BKL_FULL_BRIGHTNESS;
+}
+
+static void led_bl_set_brightness(struct led_bl_data *priv, int level)
+{
+ int i;
+ int bkl_brightness;
+
+ if (priv->levels)
+ bkl_brightness = priv->levels[level];
+ else
+ bkl_brightness = level;
+
+ for (i = 0; i < priv->nb_leds; i++) {
+ int led_brightness;
+ struct led_classdev *led = priv->leds[i];
+
+ led_brightness = to_led_brightness(led, bkl_brightness);
+ led_set_brightness(led, led_brightness);
+ }
+
+ priv->enabled = true;
+}
+
+static void led_bl_power_off(struct led_bl_data *priv)
+{
+ int i;
+
+ if (!priv->enabled)
+ return;
+
+ for (i = 0; i < priv->nb_leds; i++)
+ led_set_brightness(priv->leds[i], LED_OFF);
+
+ priv->enabled = false;
+}
+
+static int led_bl_update_status(struct backlight_device *bl)
+{
+ struct led_bl_data *priv = bl_get_data(bl);
+ int brightness = bl->props.brightness;
+
+ if (bl->props.power != FB_BLANK_UNBLANK ||
+ bl->props.fb_blank != FB_BLANK_UNBLANK ||
+ bl->props.state & BL_CORE_FBBLANK)
+ brightness = 0;
+
+ if (brightness > 0)
+ led_bl_set_brightness(priv, brightness);
+ else
+ led_bl_power_off(priv);
+
+ return 0;
+}
+
+static const struct backlight_ops led_bl_ops = {
+ .update_status = led_bl_update_status,
+};
+
+static int led_bl_parse_dt(struct device *dev,
+ struct led_bl_data *priv)
+{
+ struct device_node *node = dev->of_node;
+ int num_levels;
+ u32 *levels = NULL;
+ u32 value;
+ int ret;
+ bool use_default_levels = false;
+
+ if (!node)
+ return -ENODEV;
+
+ num_levels = of_property_count_u32_elems(node, "brightness-levels");
+ if (num_levels < 0) {
+ dev_warn(dev, "can't get brightness-levels. using default levels\n");
+ use_default_levels = true;
+ num_levels = BKL_FULL_BRIGHTNESS + 1;
+ }
+
+ if (!use_default_levels) {
+ levels = devm_kzalloc(dev, sizeof(u32) * num_levels,
+ GFP_KERNEL);
+ if (!levels)
+ return -ENOMEM;
+
+ ret = of_property_read_u32_array(node, "brightness-levels",
+ levels,
+ num_levels);
+ if (ret < 0)
+ return ret;
+ }
+
+ ret = of_property_read_u32(node, "default-brightness-level", &value);
+ if (ret < 0)
+ value = num_levels / 2;
+
+ if (value >= num_levels) {
+ dev_warn(dev, "invalid default-brightness-level. using default\n");
+ value = num_levels / 2;
+ }
+
+ ret = of_count_phandle_with_args(node, "leds", NULL);
+ if (ret < 0) {
+ dev_err(dev, "unable to get led count\n");
+ return -EINVAL;
+ }
+
+ priv->nb_leds = ret;
+ if (priv->nb_leds < 1) {
+ dev_err(dev, "At least one LED must be specified!\n");
+ return -EINVAL;
+ }
+
+ priv->levels = levels;
+ priv->max_brightness = num_levels - 1;
+ priv->default_brightness = value;
+
+ return 0;
+}
+
+static int led_bl_probe(struct platform_device *pdev)
+{
+ struct backlight_properties props;
+ struct led_bl_data *priv;
+ int ret;
+ int i;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, priv);
+
+ priv->dev = &pdev->dev;
+
+ ret = led_bl_parse_dt(&pdev->dev, priv);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "failed to parse DT data\n");
+ return ret;
+ }
+ priv->leds = devm_kzalloc(&pdev->dev,
+ sizeof(struct led_classdev *) * priv->nb_leds,
+ GFP_KERNEL);
+ if (!priv->leds)
+ return -ENOMEM;
+
+ for (i = 0; i < priv->nb_leds; i++) {
+ priv->leds[i] = devm_led_get(&pdev->dev, i);
+ if (IS_ERR(priv->leds[i]))
+ return PTR_ERR(priv->leds[i]);
+ }
+
+ memset(&props, 0, sizeof(struct backlight_properties));
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = priv->max_brightness;
+ priv->bl_dev = backlight_device_register(dev_name(&pdev->dev),
+ &pdev->dev, priv, &led_bl_ops, &props);
+ if (IS_ERR(priv->bl_dev)) {
+ dev_err(&pdev->dev, "failed to register backlight\n");
+ ret = PTR_ERR(priv->bl_dev);
+ goto err;
+ }
+
+ priv->bl_dev->props.brightness = priv->default_brightness;
+ backlight_update_status(priv->bl_dev);
+
+ return 0;
+
+err:
+ return ret;
+}
+
+static int led_bl_remove(struct platform_device *pdev)
+{
+ struct led_bl_data *priv = platform_get_drvdata(pdev);
+ struct backlight_device *bl = priv->bl_dev;
+
+ backlight_device_unregister(bl);
+
+ led_bl_power_off(priv);
+
+ return 0;
+}
+
+static const struct of_device_id led_bl_of_match[] = {
+ { .compatible = "led-backlight" },
+ { }
+};
+
+MODULE_DEVICE_TABLE(of, led_bl_of_match);
+
+static struct platform_driver led_bl_driver = {
+ .driver = {
+ .name = "led-backlight",
+ .of_match_table = of_match_ptr(led_bl_of_match),
+ },
+ .probe = led_bl_probe,
+ .remove = led_bl_remove,
+};
+
+module_platform_driver(led_bl_driver);
+
+MODULE_DESCRIPTION("LED based Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:led-backlight");
--
2.17.1
If the LED is acquired by a consumer device with devm_led_get(), it is
automatically release when the device is detach.
Signed-off-by: Jean-Jacques Hiblot <[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 0f67b13b0f1f..521cb76fbaf7 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -264,6 +264,48 @@ 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
Add DT binding for led-backlight.
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
---
.../bindings/leds/backlight/led-backlight.txt | 29 +++++++++++++++++++
1 file changed, 29 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..4f545316b288
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
@@ -0,0 +1,29 @@
+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. These
+ are in the range from 0 to 255. The actual brightness
+ level programmed in each LED will be adjusted based on
+ its maximum brightness:
+ led brightness = (level * maximum brightness) / 255
+
+ - default-brightness-level: The default brightness level (index into the
+ array defined by the "brightness-levels" property).
+
+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
On Mon, Jul 08, 2019 at 12:26:59PM +0200, Jean-Jacques Hiblot wrote:
> Add DT binding for led-backlight.
>
> Signed-off-by: Jean-Jacques Hiblot <[email protected]>
> ---
> .../bindings/leds/backlight/led-backlight.txt | 29 +++++++++++++++++++
> 1 file changed, 29 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..4f545316b288
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> @@ -0,0 +1,29 @@
> +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. These
> + are in the range from 0 to 255. The actual brightness
> + level programmed in each LED will be adjusted based on
> + its maximum brightness:
> + led brightness = (level * maximum brightness) / 255
8-bits is a narrow range and likely to make animated backlight effects
impossible because the stepping artefacts would be too obvious.
I'd rather see the brightness-levels table expressed in the native
steps of the LEDs in the leds list.
I know this means that the LEDs must have identical ranges but I think
it is OK. A backlight design whose LEDs are connected to non-identical
drivers is either badly broken or sufficiently exotic to need to special
purpose driver. The driver can therefore fail to probe if the LEDs are
mismatched.
> +
> + - default-brightness-level: The default brightness level (index into the
> + array defined by the "brightness-levels" property).
The brightness-levels property is optional... this text needs to be
updated.
Daniel.
On Mon, Jul 08, 2019 at 12:27:00PM +0200, Jean-Jacques Hiblot wrote:
> From: Tomi Valkeinen <[email protected]>
>
> This patch adds a led-backlight driver (led_bl), which is similar to
> pwm_bl except the driver uses a LED class driver to adjust the
> brightness in the HW. Multiple LEDs can be used for a single backlight.
>
> Signed-off-by: Tomi Valkeinen <[email protected]>
> Signed-off-by: Jean-Jacques Hiblot <[email protected]>
> ---
> drivers/video/backlight/Kconfig | 7 +
> drivers/video/backlight/Makefile | 1 +
> drivers/video/backlight/led_bl.c | 235 +++++++++++++++++++++++++++++++
> 3 files changed, 243 insertions(+)
> create mode 100644 drivers/video/backlight/led_bl.c
> diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
> new file mode 100644
> index 000000000000..7644277cfdbb
> --- /dev/null
> +++ b/drivers/video/backlight/led_bl.c
> @@ -0,0 +1,235 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2015-2019 Texas Instruments Incorporated - http://www.ti.com/
> + * Author: Tomi Valkeinen <[email protected]>
> + *
> + * Based on pwm_bl.c
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/gpio/consumer.h>
Header should no longer be needed.
> +static int led_bl_probe(struct platform_device *pdev)
> +{
> + struct backlight_properties props;
> + struct led_bl_data *priv;
> + int ret;
> + int i;
> +
> + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + platform_set_drvdata(pdev, priv);
> +
> + priv->dev = &pdev->dev;
> +
> + ret = led_bl_parse_dt(&pdev->dev, priv);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "failed to parse DT data\n");
> + return ret;
> + }
> + priv->leds = devm_kzalloc(&pdev->dev,
> + sizeof(struct led_classdev *) * priv->nb_leds,
> + GFP_KERNEL);
> + if (!priv->leds)
> + return -ENOMEM;
> +
> + for (i = 0; i < priv->nb_leds; i++) {
> + priv->leds[i] = devm_led_get(&pdev->dev, i);
> + if (IS_ERR(priv->leds[i]))
> + return PTR_ERR(priv->leds[i]);
> + }
> +
> + memset(&props, 0, sizeof(struct backlight_properties));
> + props.type = BACKLIGHT_RAW;
> + props.max_brightness = priv->max_brightness;
> + priv->bl_dev = backlight_device_register(dev_name(&pdev->dev),
> + &pdev->dev, priv, &led_bl_ops, &props);
> + if (IS_ERR(priv->bl_dev)) {
> + dev_err(&pdev->dev, "failed to register backlight\n");
> + ret = PTR_ERR(priv->bl_dev);
> + goto err;
goto is pointless for a pure-devm function.
> + }
> +
> + priv->bl_dev->props.brightness = priv->default_brightness;
> + backlight_update_status(priv->bl_dev);
This will light up the backlight during backlight probe.
Can you take a look at pwm_backlight_initial_power_state() and decide
how much of it applies to an LED based backlight (the phandle stuff
certainly does).
Daniel.