Hi Pavel
On 06/07/2019 17:19, Pavel Machek wrote:
Hi!
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 he lacked the time to work on it.
I will be taking over the task and, before heading in the wrong
direction, wanted a confirmation that the binding Tomi last proposed in
hist last email was indeed the preferred option.
It will probably require some modifications in the LED core to create
the right kind of led-device (normal, flash or backlight) based on the
compatible option.
I recall that discussion. I gave my ack for the LED changes but
now we have more LED people that might want to look into that.
Regarding the LED bindings as discussed by Tom and Rob in
https://patchwork.kernel.org/patch/7293991/, what do you think of using
a 'compatible' string to make a LED device also a backlight or a flash LED ?
After going through the referenced discussion and refreshing my memory
it looks to me the most reasonable way to go for backlight case.
Nevertheless I'd not tamper at LED flash support - if it's not broken,
don't fix it.
Best regards,
Jacek Anaszewski
Here is the example from Tomi at the end of the discussion:
/* tlc59108 is an i2c device */
tlc59116@40 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "ti,tlc59108";
reg = <0x40>;
wan@0 {
label = "wrt1900ac:amber:wan";
reg = <0x0>;
};
bl@2 {
label = "backlight";
reg = <0x2>;
compatible = "led-backlight";
brightness-levels = <0 243 245 247 248 249 251 252 255>;
default-brightness-level = <8>;
enable-gpios = <&pcf_lcd 13 GPIO_ACTIVE_LOW>;
So... this needs some kind of reference to display it belongs to,
right?
This is the reverse. The display uses a reference the backlight.
JJ
Pavel
