Re: [PATCH 1/1] Documentation: leds: leds-class: Document keyboard backlight LED class naming

[Lee Jones <lee@kernel.org>]

On Mon, 06 Apr 2026, Hans de Goede wrote:

> From: Carlos Ferreira <carlosmiguelferreira.2003@gmail.com>
> 
> Document the existing practice of always using 'kbd_backlight' for
> the function part of LED class device names for LED class devices which
> control single-zone keyboard backlights.
> 
> Also extend this existing practice with a new naming scheme for keyboards
> with zoned backlight control. There are several drivers in the works (see
> the Link:tags below) which offer backlight control for keyboards where
> the keyboard backlight is divided in a limited number of zones, e.g.
> "main", "cursor" and "numpad" zones.
> 
> It is important to agree on a consistent naming scheme for these now,
> so that userspace can support multiple different models / vendors through
> a single unified naming scheme.
> 
> Link: https://lore.kernel.org/platform-driver-x86/20230131235027.36304-1-rishitbansal0@gmail.com/
> Link: https://lore.kernel.org/platform-driver-x86/20240719100011.16656-1-carlosmiguelferreira.2003@gmail.com/
> Link: https://lore.kernel.org/platform-driver-x86/20260304105831.119349-3-edip@medip.dev/
> Link: https://lore.kernel.org/platform-driver-x86/20240806205001.191551-2-mustafa.eskieksi@gmail.com/
> Link: https://lore.kernel.org/linux-input/20260402075239.3829699-1-xav@bes.tel/
> Signed-off-by: Carlos Ferreira <carlosmiguelferreira.2003@gmail.com>
> Co-authored-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
> Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>

The premise is fine I think.

> ---
>  Documentation/leds/leds-class.rst | 63 +++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
> 
> diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
> index 5db620ed27aa..d2b042519a66 100644
> --- a/Documentation/leds/leds-class.rst
> +++ b/Documentation/leds/leds-class.rst
> @@ -116,6 +116,69 @@ above leaves scope for further attributes should they be needed. If sections
>  of the name don't apply, just leave that section blank.
>  
>  
> +Keyboard backlight control LED Device Naming
> +============================================
> +
> +For backlit keyboards with a single brightness / color settings a single
> +(multicolor) LED class device should be used to allow userspace to change
> +the backlight brightness (and if possible the color). This LED class device
> +must use "kbd_backlight" for the function part of the LED class device name.
> +IOW the name must end with ":kbd_backlight".
> +
> +For backlit keyboards with multiple control zones, one (multicolor) LED class
> +device should be used per zone. These LED class devices' name must follow:
> +
> +	"<devicename>:<color>:kbd_zoned_backlight-<zone_name>"
> +
> +and <devicename> must be the same for all zones of the same keyboard.
> +
> +<zone_name> should be descriptive of which part of the keyboard backlight
> +the zone covers and should be suitable for userspace to show to an end user
> +in an UI for controlling the zones.
> +
> +Where possible <zone_name> should be a value already used by other
> +zoned keyboards with a similar or identical zone layout, e.g.:
> +
> +<devicename>:<color>:kbd_zoned_backlight-right
> +<devicename>:<color>:kbd_zoned_backlight-middle
> +<devicename>:<color>:kbd_zoned_backlight-left
> +<devicename>:<color>:kbd_zoned_backlight-corners
> +<devicename>:<color>:kbd_zoned_backlight-wasd
> +
> +or:
> +
> +<devicename>:<color>:kbd_zoned_backlight-main
> +<devicename>:<color>:kbd_zoned_backlight-cursor
> +<devicename>:<color>:kbd_zoned_backlight-numpad
> +<devicename>:<color>:kbd_zoned_backlight-corners
> +<devicename>:<color>:kbd_zoned_backlight-wasd
> +
> +Note that this is intended for keyboards with a limited number of zones,
> +keyboards with per key addressable backlighting must not use LED class devices
> +since the sysfs API is not suitable for rapidly change multiple LEDs in one
> +"commit" as is necessary to do animations / special effects on such keyboards.
> +
> +An exception to the rule that all zones must follow:
> +
> +	"<devicename>:<color>:kbd_zoned_backlight-<zone_name>"
> +
> +is made for the special case where there is a single big zone which controls
> +the backlighting of almost all of the keyboard and there are some small areas
> +with separate control, like just the 4 cursor keys, or the WASD keys. In this
> +case the main zone should use 'kbd_backlight' for the function part of the name
> +for compatiblity with (older) userspace code which is not aware of

Nit: compatibility

There may be others.  Please run it through a spell checker.

> +the "kbd_zoned_backlight-<zone_name>" function naming scheme.
> +
> +While the smaller zones should use the new zoned naming scheme. Such a setup
> +would result in e.g.:
> +
> +<devicename>:<color>:kbd_backlight
> +<devicename>:<color>:kbd_zoned_backlight-wasd
> +
> +"kbd_zoned_backlight-<zone_name>" aware userspace should be aware of this
> +exception and check for a main zone with a "kbd_backlight" function-name.
> +
> +
>  Brightness setting API
>  ======================
>  
> -- 
> 2.53.0
> 

-- 
Lee Jones