Hi Sakari,
Thanks for the patch.
On 09/15/2017 04:40 PM, Sakari Ailus wrote:
> Document referring to LEDs from remote device nodes, such as from camera
> sensors.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> ---
> Documentation/acpi/dsd/leds.txt | 94 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 94 insertions(+)
> create mode 100644 Documentation/acpi/dsd/leds.txt
>
> diff --git a/Documentation/acpi/dsd/leds.txt b/Documentation/acpi/dsd/leds.txt
> new file mode 100644
> index 000000000000..894c82274f53
> --- /dev/null
> +++ b/Documentation/acpi/dsd/leds.txt
> @@ -0,0 +1,94 @@
> +Describing and referring to LEDs in ACPI
> +
> +Individual LEDs are described by hierarchical data extension [6] nodes
> +under the device node, the LED driver chip. The "led" property in the
> +LED specific nodes tells the numerical ID of each individual LED. The
> +"led" property is used here in a similar fashion as the "reg" property
> +in DT. [3]
> +
> +Referring to LEDs in Device tree is documented in [4], in "flash-leds"
> +property documentation. In short, LEDs are directly referred to by
> +using phandles.
> +
> +While Device tree allows referring to any node in the tree[1], in ACPI
> +references are limited to device nodes only [2]. For this reason using
> +the same mechanism on ACPI is not possible.
> +
> +ACPI allows (as does DT) using integer arguments after the reference.
> +A combination of the LED driver device reference and an integer
> +argument, referring to the "led" property of the relevant LED, are
> +use to individual LEDs.
s/are use/is used/ ? (in a sense "combination of ... and .. is used")
s/to individual/to describe individual/
(or another verb, I'm not sure what exactly you intended it to be)
The value of the LED property is a contract
> +between the firmware and software, it uniquely identifies the LED
> +driver outputs.
> +
> +An ASL example of a camera sensor device and a LED driver device for two
> +LEDs. Objects not relevant for LEDs or the references to them have been
> +omitted.
> +
> + Device (LED)
> + {
> + Name (_DSD, Package () {
> + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
> + Package () {
> + Package () { "led0", LED0 },
> + Package () { "led1", LED1 },
> + }
> + })
> + Name (LED0, Package () {
> + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> + Package () {
> + Package () { "led", 0 },
> + Package () { "flash-max-microamp", 1000000 },
> + Package () { "flash-timeout-us", 200000 },
> + Package () { "led-max-microamp", 100000 },
> + Package () { "label", "led:salama" },
> + }
> + })
> + Name (LED1, Package () {
> + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> + Package () {
> + Package () { "led", 1 },
> + Package () { "led-max-microamp", 10000 },
> + Package () { "label", "led:huomiovalo" },
> + }
> + })
> + }
> +
> + Device (SEN)
> + {
> + Name (_DSD, Package () {
> + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> + Package () {
> + Package () {
> + "flash-leds",
> + Package () { ^LED, 0, ^LED, 1 },
> + }
> + }
> + })
> + }
> +
> +where
> +
> + LED LED driver device
> + LED0 First LED
> + LED1 Second LED
> + SEN Camera sensor device (or another device the LED is
> + related to)
> +
> +[1] Device tree. <URL:http://www.devicetree.org>, referenced 2016-10-03.
> +
> +[2] Advanced Configuration and Power Interface Specification.
> + <URL:http://www.uefi.org/sites/default/files/resources/ACPI_6_1.pdf>,
> + referenced 2016-10-04.
> +
> +[3] Documentation/devicetree/bindings/leds/common.txt
> +
> +[4] Documentation/devicetree/bindings/media/video-interfaces.txt
> +
> +[5] Device Properties UUID For _DSD.
> + <URL:http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>,
> + referenced 2016-10-04.
> +
> +[6] Hierarchical Data Extension UUID For _DSD.
> + <URL:http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.pdf>,
> + referenced 2016-10-04.
>
--
Best regards,
Jacek Anaszewski
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