[PATCH v9 0/5] Add a generic driver for LED-based backlight

[PATCH v9 0/5] Add a generic driver for LED-based backlight

[Jean-Jacques Hiblot]

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 v9:
- let to_of_node() check if the fwnode is actually a of_node
- add some checks in of_led_get()
- let dev_of_node() do the check about OF availabilty
- refactor led_bl_probe() to register a cleanup function with
  devm_add_action_or_reset(). This simplifies the error handling (which
  was not 100% done in v7) and allows to get rid of led_bl_remove()

changes in v8:
- use class_find_device_by_of_node() instead of class_find_device()
- renamed devm_led_get() as devm_of_led_get()

changes in v7:
- rebased on top of linux-leds/for-next
- populate the of_node member of the LED device if fwnode is a of_node
  (this is a new patch and the first of the series).
- devm_led_get() works only when the device tree is used. Add a few checks
  for that.  

changes in v6:
- trim the list of included headers
- remove useless definition of BKL_FULL_BRIGHTNESS

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 (3):
  leds: populate the device's of_node
  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                      | 103 ++++++-
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 258 ++++++++++++++++++
 include/linux/leds.h                          |   6 +
 6 files changed, 402 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c

-- 
2.17.1

[PATCH v9 1/5] leds: populate the device's of_node

[Jean-Jacques Hiblot]

If initialization data is available and its fwnode is actually a of_node,
store this information in the led device's structure. This will allow the
device to use or provide OF-based API such (devm_xxx).

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
---
 drivers/leds/led-class.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 647b1263c579..bfa1b1033274 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -276,8 +276,10 @@ int led_classdev_register_ext(struct device *parent,
 		mutex_unlock(&led_cdev->led_access);
 		return PTR_ERR(led_cdev->dev);
 	}
-	if (init_data && init_data->fwnode)
+	if (init_data && init_data->fwnode) {
 		led_cdev->dev->fwnode = init_data->fwnode;
+		led_cdev->dev->of_node = to_of_node(init_data->fwnode);
+	}
 
 	if (ret)
 		dev_warn(parent, "Led %s renamed to %s due to name collision",
-- 
2.17.1

[PATCH v9 2/5] leds: Add of_led_get() and led_put()

[Jean-Jacques Hiblot]

From: Tomi Valkeinen <tomi.valkeinen@ti.com>

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 <tomi.valkeinen@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
---
 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 bfa1b1033274..1d1f1d546dc7 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -19,6 +19,7 @@
 #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;
@@ -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);
 
+/**
+ * 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;
+
+	/* Not using device tree? */
+	if (!IS_ENABLED(CONFIG_OF))
+		return ERR_PTR(-ENOTSUPP);
+	if (!np)
+		return ERR_PTR(-EINVAL);
+
+	led_node = of_parse_phandle(np, "leds", index);
+	if (!led_node)
+		return ERR_PTR(-ENOENT);
+
+	led_dev = class_find_device_by_of_node(leds_class, 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 led_classdev_next_name(const char *init_name, char *name,
 				  size_t len)
 {
diff --git a/include/linux/leds.h b/include/linux/leds.h
index b8df71193329..6f7371bc7757 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -20,6 +20,7 @@
 
 struct device;
 struct led_pattern;
+struct device_node;
 /*
  * LED Core
  */
@@ -196,6 +197,9 @@ 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

[PATCH v9 3/5] leds: Add managed API to get a LED from a device driver

[Jean-Jacques Hiblot]

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 <jjhiblot@ti.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
---
 drivers/leds/led-class.c | 49 ++++++++++++++++++++++++++++++++++++++++
 include/linux/leds.h     |  2 ++
 2 files changed, 51 insertions(+)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 1d1f1d546dc7..639224392ffa 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -264,6 +264,55 @@ 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_of_led_get - Resource-managed request of a LED device
+ * @dev:	LED consumer
+ * @index:	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_of_led_get(struct device *dev,
+						  int index)
+{
+	struct led_classdev *led;
+	struct led_classdev **dr;
+
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	/* Consummer not using device tree? */
+	if (!dev_of_node(dev))
+		return ERR_PTR(-ENOTSUPP);
+
+	led = of_led_get(dev_of_node(dev), 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_of_led_get);
+
 static int led_classdev_next_name(const char *init_name, char *name,
 				  size_t len)
 {
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 6f7371bc7757..9b94cf752012 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -199,6 +199,8 @@ 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_of_led_get(struct device *dev,
+						  int index);
 
 /**
  * led_blink_set - set blinking with software fallback
-- 
2.17.1

Re: [PATCH v9 3/5] leds: Add managed API to get a LED from a device driver

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 1757 bytes --]

Hi!

> 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 <jjhiblot@ti.com>
> Acked-by: Pavel Machek <pavel@ucw.cz>
> ---
>  drivers/leds/led-class.c | 49 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/leds.h     |  2 ++
>  2 files changed, 51 insertions(+)
> 
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 1d1f1d546dc7..639224392ffa 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -264,6 +264,55 @@ 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_of_led_get - Resource-managed request of a LED device
> + * @dev:	LED consumer
> + * @index:	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_of_led_get(struct device *dev,
> +						  int index)
> +{
> +	struct led_classdev *led;
> +	struct led_classdev **dr;
> +
> +	if (!dev)
> +		return ERR_PTR(-EINVAL);
> +
> +	/* Consummer not using device tree? */

Typo "consumer". I may fix it before applying the patch.

Best regards,
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[-- Attachment #2: Digital signature --]
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[PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Jean-Jacques Hiblot]

Add DT binding for led-backlight.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
 .../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

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Rob Herring]

Please send DT bindings to DT list or it's never in my queue. IOW,
send patches to the lists that get_maintainers.pl tells you to.

On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>
> Add DT binding for led-backlight.
>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
> ---
>  .../bindings/leds/backlight/led-backlight.txt | 28 +++++++++++++++++++
>  1 file changed, 28 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt

Please make this a DT schema.

> 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

'leds' is already used as a node name and mixing is not ideal.

We already have 'flash-leds' in use and with the same definition, so
lets continue that and use 'backlight-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.

You can just assume these 2 get a common schema at some point. So just
need to define any additional constraints if possible.

Rob

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Jean-Jacques Hiblot]

Hi Rob,

On 07/10/2019 18:15, Rob Herring wrote:
> Please send DT bindings to DT list or it's never in my queue. IOW,
> send patches to the lists that get_maintainers.pl tells you to.
>
> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>> Add DT binding for led-backlight.
>>
>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
>> ---
>>   .../bindings/leds/backlight/led-backlight.txt | 28 +++++++++++++++++++
>>   1 file changed, 28 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> Please make this a DT schema.

OK.

BTW I used "make dt_binding_check" but had to fix a couple of YAMLs file 
to get it to work. Do you have a kernel tree with already all the YAML 
files in good shape ? Or do you want me to post the changes to 
devicetree@vger.kernel.org ?


>
>> 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
> 'leds' is already used as a node name and mixing is not ideal.
>
> We already have 'flash-leds' in use and with the same definition, so
> lets continue that and use 'backlight-leds'.
OK
>
>> +
>> +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.
> You can just assume these 2 get a common schema at some point. So just
> need to define any additional constraints if possible.

Maybe we should keep them until such a common schema is written ?

JJ

>
> Rob

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Jean-Jacques Hiblot]

Rob,

On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
> Hi Rob,
>
> On 07/10/2019 18:15, Rob Herring wrote:
>> Please send DT bindings to DT list or it's never in my queue. IOW,
>> send patches to the lists that get_maintainers.pl tells you to.
>>
>> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com> 
>> wrote:
>>> Add DT binding for led-backlight.
>>>
>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
>>> ---
>>>   .../bindings/leds/backlight/led-backlight.txt | 28 
>>> +++++++++++++++++++
>>>   1 file changed, 28 insertions(+)
>>>   create mode 100644 
>>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>> Please make this a DT schema.
>
> OK.
>
> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs 
> file to get it to work. Do you have a kernel tree with already all the 
> YAML files in good shape ? Or do you want me to post the changes to 
> devicetree@vger.kernel.org ?
>
>
>>
>>> 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
>> 'leds' is already used as a node name and mixing is not ideal.
>>
>> We already have 'flash-leds' in use and with the same definition, so
>> lets continue that and use 'backlight-leds'.
> OK

I am taking that back. I have added of_get_led() and devm_of_get_led() 
to the LED core to make it easier to get a LED from the DT. I modeled 
the interface like it is done for PWM, PHYs or clocks. The property 
containing list/array of phandle  is always named the same. To get one 
particular PWM/PHY/clock, a identifier (name or integer) must be provided.

So unless there is a strong incentive to do otherwise I's rather keep 
this name here.


JJ


>>> +
>>> +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.
>> You can just assume these 2 get a common schema at some point. So just
>> need to define any additional constraints if possible.
>
> Maybe we should keep them until such a common schema is written ?
>
> JJ
>
>>
>> Rob

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Rob Herring]

On Tue, Oct 8, 2019 at 8:30 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>
> Rob,
>
> On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
> > Hi Rob,
> >
> > On 07/10/2019 18:15, Rob Herring wrote:
> >> Please send DT bindings to DT list or it's never in my queue. IOW,
> >> send patches to the lists that get_maintainers.pl tells you to.
> >>
> >> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com>
> >> wrote:
> >>> Add DT binding for led-backlight.
> >>>
> >>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> >>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> >>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
> >>> ---
> >>>   .../bindings/leds/backlight/led-backlight.txt | 28
> >>> +++++++++++++++++++
> >>>   1 file changed, 28 insertions(+)
> >>>   create mode 100644
> >>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> >> Please make this a DT schema.
> >
> > OK.
> >
> > BTW I used "make dt_binding_check" but had to fix a couple of YAMLs
> > file to get it to work. Do you have a kernel tree with already all the
> > YAML files in good shape ? Or do you want me to post the changes to
> > devicetree@vger.kernel.org ?
> >
> >
> >>
> >>> 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
> >> 'leds' is already used as a node name and mixing is not ideal.
> >>
> >> We already have 'flash-leds' in use and with the same definition, so
> >> lets continue that and use 'backlight-leds'.
> > OK
>
> I am taking that back. I have added of_get_led() and devm_of_get_led()
> to the LED core to make it easier to get a LED from the DT. I modeled
> the interface like it is done for PWM, PHYs or clocks. The property
> containing list/array of phandle  is always named the same. To get one
> particular PWM/PHY/clock, a identifier (name or integer) must be provided.

It can be done as we do support that with '-gpios', but yes, it is a
bit more painful to deal with.

> So unless there is a strong incentive to do otherwise I's rather keep
> this name here.

In that case, this needs to be documented as a common LED binding, not
something hidden away in this binding.

Rob

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Jacek Anaszewski]

On 10/8/19 5:00 PM, Rob Herring wrote:
> On Tue, Oct 8, 2019 at 8:30 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>>
>> Rob,
>>
>> On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
>>> Hi Rob,
>>>
>>> On 07/10/2019 18:15, Rob Herring wrote:
>>>> Please send DT bindings to DT list or it's never in my queue. IOW,
>>>> send patches to the lists that get_maintainers.pl tells you to.
>>>>
>>>> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com>
>>>> wrote:
>>>>> Add DT binding for led-backlight.
>>>>>
>>>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>>>>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
>>>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
>>>>> ---
>>>>>   .../bindings/leds/backlight/led-backlight.txt | 28
>>>>> +++++++++++++++++++
>>>>>   1 file changed, 28 insertions(+)
>>>>>   create mode 100644
>>>>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>>>> Please make this a DT schema.
>>>
>>> OK.
>>>
>>> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs
>>> file to get it to work. Do you have a kernel tree with already all the
>>> YAML files in good shape ? Or do you want me to post the changes to
>>> devicetree@vger.kernel.org ?
>>>
>>>
>>>>
>>>>> 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
>>>> 'leds' is already used as a node name and mixing is not ideal.

for the record: child node names (if that was what you had on mind)
have singular form 'led'.

>>>> We already have 'flash-leds' in use and with the same definition, so
>>>> lets continue that and use 'backlight-leds'.
>>> OK
>>
>> I am taking that back. I have added of_get_led() and devm_of_get_led()
>> to the LED core to make it easier to get a LED from the DT. I modeled
>> the interface like it is done for PWM, PHYs or clocks. The property
>> containing list/array of phandle  is always named the same. To get one
>> particular PWM/PHY/clock, a identifier (name or integer) must be provided.
> 
> It can be done as we do support that with '-gpios', but yes, it is a
> bit more painful to deal with.
> 
>> So unless there is a strong incentive to do otherwise I's rather keep
>> this name here.
> 
> In that case, this needs to be documented as a common LED binding, not
> something hidden away in this binding.
> 
> Rob
> 

-- 
Best regards,
Jacek Anaszewski

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Jacek Anaszewski]

On 10/8/19 5:00 PM, Rob Herring wrote:
> On Tue, Oct 8, 2019 at 8:30 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>>
>> Rob,
>>
>> On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
>>> Hi Rob,
>>>
>>> On 07/10/2019 18:15, Rob Herring wrote:
>>>> Please send DT bindings to DT list or it's never in my queue. IOW,
>>>> send patches to the lists that get_maintainers.pl tells you to.
>>>>
>>>> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com>
>>>> wrote:
>>>>> Add DT binding for led-backlight.
>>>>>
>>>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>>>>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
>>>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
>>>>> ---
>>>>>   .../bindings/leds/backlight/led-backlight.txt | 28
>>>>> +++++++++++++++++++
>>>>>   1 file changed, 28 insertions(+)
>>>>>   create mode 100644
>>>>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>>>> Please make this a DT schema.
>>>
>>> OK.
>>>
>>> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs
>>> file to get it to work. Do you have a kernel tree with already all the
>>> YAML files in good shape ? Or do you want me to post the changes to
>>> devicetree@vger.kernel.org ?
>>>
>>>
>>>>
>>>>> 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
>>>> 'leds' is already used as a node name and mixing is not ideal.

for the record: child node names (if that was what you had on mind)
have singular form 'led'.

>>>> We already have 'flash-leds' in use and with the same definition, so
>>>> lets continue that and use 'backlight-leds'.
>>> OK
>>
>> I am taking that back. I have added of_get_led() and devm_of_get_led()
>> to the LED core to make it easier to get a LED from the DT. I modeled
>> the interface like it is done for PWM, PHYs or clocks. The property
>> containing list/array of phandle  is always named the same. To get one
>> particular PWM/PHY/clock, a identifier (name or integer) must be provided.
> 
> It can be done as we do support that with '-gpios', but yes, it is a
> bit more painful to deal with.
> 
>> So unless there is a strong incentive to do otherwise I's rather keep
>> this name here.
> 
> In that case, this needs to be documented as a common LED binding, not
> something hidden away in this binding.
> 
> Rob
> 

-- 
Best regards,
Jacek Anaszewski

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Rob Herring]

On Tue, Oct 8, 2019 at 12:17 PM Jacek Anaszewski
<jacek.anaszewski@gmail.com> wrote:
>
> On 10/8/19 5:00 PM, Rob Herring wrote:
> > On Tue, Oct 8, 2019 at 8:30 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
> >>
> >> Rob,
> >>
> >> On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
> >>> Hi Rob,
> >>>
> >>> On 07/10/2019 18:15, Rob Herring wrote:
> >>>> Please send DT bindings to DT list or it's never in my queue. IOW,
> >>>> send patches to the lists that get_maintainers.pl tells you to.
> >>>>
> >>>> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com>
> >>>> wrote:
> >>>>> Add DT binding for led-backlight.
> >>>>>
> >>>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> >>>>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> >>>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
> >>>>> ---
> >>>>>   .../bindings/leds/backlight/led-backlight.txt | 28
> >>>>> +++++++++++++++++++
> >>>>>   1 file changed, 28 insertions(+)
> >>>>>   create mode 100644
> >>>>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> >>>> Please make this a DT schema.
> >>>
> >>> OK.
> >>>
> >>> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs
> >>> file to get it to work. Do you have a kernel tree with already all the
> >>> YAML files in good shape ? Or do you want me to post the changes to
> >>> devicetree@vger.kernel.org ?
> >>>
> >>>
> >>>>
> >>>>> 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
> >>>> 'leds' is already used as a node name and mixing is not ideal.
>
> for the record: child node names (if that was what you had on mind)
> have singular form 'led'.

I did actually grep this and not rely on my somewhat faulty memory:

$ git grep '\sleds {' | wc -l
463

These are mostly gpio-leds I think.

Rob

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Jacek Anaszewski]

On 10/8/19 10:00 PM, Rob Herring wrote:
> On Tue, Oct 8, 2019 at 12:17 PM Jacek Anaszewski
> <jacek.anaszewski@gmail.com> wrote:
>>
>> On 10/8/19 5:00 PM, Rob Herring wrote:
>>> On Tue, Oct 8, 2019 at 8:30 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>>>>
>>>> Rob,
>>>>
>>>> On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
>>>>> Hi Rob,
>>>>>
>>>>> On 07/10/2019 18:15, Rob Herring wrote:
>>>>>> Please send DT bindings to DT list or it's never in my queue. IOW,
>>>>>> send patches to the lists that get_maintainers.pl tells you to.
>>>>>>
>>>>>> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com>
>>>>>> wrote:
>>>>>>> Add DT binding for led-backlight.
>>>>>>>
>>>>>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>>>>>>> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
>>>>>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
>>>>>>> ---
>>>>>>>   .../bindings/leds/backlight/led-backlight.txt | 28
>>>>>>> +++++++++++++++++++
>>>>>>>   1 file changed, 28 insertions(+)
>>>>>>>   create mode 100644
>>>>>>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>>>>>> Please make this a DT schema.
>>>>>
>>>>> OK.
>>>>>
>>>>> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs
>>>>> file to get it to work. Do you have a kernel tree with already all the
>>>>> YAML files in good shape ? Or do you want me to post the changes to
>>>>> devicetree@vger.kernel.org ?
>>>>>
>>>>>
>>>>>>
>>>>>>> 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
>>>>>> 'leds' is already used as a node name and mixing is not ideal.
>>
>> for the record: child node names (if that was what you had on mind)
>> have singular form 'led'.
> 
> I did actually grep this and not rely on my somewhat faulty memory:
> 
> $ git grep '\sleds {' | wc -l
> 463
> 
> These are mostly gpio-leds I think.

Indeed. So this is legacy, but common LED bindings have never stated
that. If should be OK to add leds property to common bindings with
proper description.

-- 
Best regards,
Jacek Anaszewski

Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

[Rob Herring]

On Tue, Oct 8, 2019 at 7:51 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>
> Hi Rob,
>
> On 07/10/2019 18:15, Rob Herring wrote:
> > Please send DT bindings to DT list or it's never in my queue. IOW,
> > send patches to the lists that get_maintainers.pl tells you to.
> >
> > On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
> >> Add DT binding for led-backlight.
> >>
> >> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> >> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> >> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
> >> ---
> >>   .../bindings/leds/backlight/led-backlight.txt | 28 +++++++++++++++++++
> >>   1 file changed, 28 insertions(+)
> >>   create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> > Please make this a DT schema.
>
> OK.
>
> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs file
> to get it to work. Do you have a kernel tree with already all the YAML
> files in good shape ? Or do you want me to post the changes to
> devicetree@vger.kernel.org ?

linux-next is fixed now.

> >> 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
> > 'leds' is already used as a node name and mixing is not ideal.
> >
> > We already have 'flash-leds' in use and with the same definition, so
> > lets continue that and use 'backlight-leds'.
> OK
> >
> >> +
> >> +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.
> > You can just assume these 2 get a common schema at some point. So just
> > need to define any additional constraints if possible.
>
> Maybe we should keep them until such a common schema is written ?

I'm not saying to remove them, but you can just have a description if
there are no other constraints.

Rob

[PATCH v9 5/5] backlight: add led-backlight driver

[Jean-Jacques Hiblot]

From: Tomi Valkeinen <tomi.valkeinen@ti.com>

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 <tomi.valkeinen@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
 drivers/video/backlight/Kconfig  |   7 +
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/led_bl.c | 258 +++++++++++++++++++++++++++++++
 3 files changed, 266 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..b89ba20c1d16
--- /dev/null
+++ b/drivers/video/backlight/led_bl.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Texas Instruments Incorporated -  http://www.ti.com/
+ * Authors: Tomi Valkeinen <tomi.valkeinen@ti.com>
+ *          Jean-Jacques Hiblot <jjhiblot@ti.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+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 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++)
+		led_set_brightness(priv->leds[i], bkl_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_get_leds(struct device *dev,
+			   struct led_bl_data *priv)
+{
+	int i, nb_leds, ret;
+	struct device_node *node = dev->of_node;
+	struct led_classdev **leds;
+	unsigned int max_brightness;
+	unsigned int default_brightness;
+
+	ret = of_count_phandle_with_args(node, "leds", NULL);
+	if (ret < 0) {
+		dev_err(dev, "Unable to get led count\n");
+		return -EINVAL;
+	}
+
+	nb_leds = ret;
+	if (nb_leds < 1) {
+		dev_err(dev, "At least one LED must be specified!\n");
+		return -EINVAL;
+	}
+
+	leds = devm_kzalloc(dev, sizeof(struct led_classdev *) * nb_leds,
+			    GFP_KERNEL);
+	if (!leds)
+		return -ENOMEM;
+
+	for (i = 0; i < nb_leds; i++) {
+		leds[i] = devm_of_led_get(dev, i);
+		if (IS_ERR(leds[i]))
+			return PTR_ERR(leds[i]);
+	}
+
+	/* check that the LEDs all have the same brightness range */
+	max_brightness = leds[0]->max_brightness;
+	for (i = 1; i < nb_leds; i++) {
+		if (max_brightness != leds[i]->max_brightness) {
+			dev_err(dev, "LEDs must have identical ranges\n");
+			return -EINVAL;
+		}
+	}
+
+	/* get the default brightness from the first LED from the list */
+	default_brightness = leds[0]->brightness;
+
+	priv->nb_leds = nb_leds;
+	priv->leds = leds;
+	priv->max_brightness = max_brightness;
+	priv->default_brightness = default_brightness;
+
+	return 0;
+}
+
+static int led_bl_parse_levels(struct device *dev,
+			   struct led_bl_data *priv)
+{
+	struct device_node *node = dev->of_node;
+	int num_levels;
+	u32 value;
+	int ret;
+
+	if (!node)
+		return -ENODEV;
+
+	num_levels = of_property_count_u32_elems(node, "brightness-levels");
+	if (num_levels > 1) {
+		int i;
+		unsigned int db;
+		u32 *levels = NULL;
+
+		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;
+
+		/*
+		 * Try to map actual LED brightness to backlight brightness
+		 * level
+		 */
+		db = priv->default_brightness;
+		for (i = 0 ; i < num_levels; i++) {
+			if ((i && db > levels[i-1]) && db <= levels[i])
+				break;
+		}
+		priv->default_brightness = i;
+		priv->max_brightness = num_levels - 1;
+		priv->levels = levels;
+	} else if (num_levels >= 0)
+		dev_warn(dev, "Not enough levels defined\n");
+
+	ret = of_property_read_u32(node, "default-brightness-level", &value);
+	if (!ret && value <= priv->max_brightness)
+		priv->default_brightness = value;
+	else if (!ret  && value > priv->max_brightness)
+		dev_warn(dev, "Invalid default brightness. Ignoring it\n");
+
+	return 0;
+}
+
+static void led_bl_cleanup(void *data)
+{
+	struct led_bl_data *priv = data;
+	int i;
+
+	led_bl_power_off(priv);
+	for (i = 0; i < priv->nb_leds; i++)
+		led_sysfs_enable(priv->leds[i]);
+}
+
+static int led_bl_probe(struct platform_device *pdev)
+{
+	struct backlight_properties props;
+	struct led_bl_data *priv;
+	int ret, 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_get_leds(&pdev->dev, priv);
+	if (ret)
+		return ret;
+
+	ret = led_bl_parse_levels(&pdev->dev, priv);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Failed to parse DT data\n");
+		return ret;
+	}
+
+	ret = devm_add_action_or_reset(&pdev->dev, led_bl_cleanup, priv);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < priv->nb_leds; i++)
+		led_sysfs_disable(priv->leds[i]);
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = priv->max_brightness;
+	props.brightness = priv->default_brightness;
+	props.power = (priv->default_brightness > 0) ? FB_BLANK_POWERDOWN :
+		      FB_BLANK_UNBLANK;
+	priv->bl_dev = devm_backlight_device_register(&pdev->dev,
+			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");
+		return PTR_ERR(priv->bl_dev);
+	}
+
+	backlight_update_status(priv->bl_dev);
+
+	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	= led_bl_of_match,
+	},
+	.probe		= led_bl_probe,
+};
+
+module_platform_driver(led_bl_driver);
+
+MODULE_DESCRIPTION("LED based Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:led-backlight");
-- 
2.17.1