Re: [RFC PATCH v3 1/8] leds: add support for hardware driven LEDs
From: Randy Dunlap <hidden>
Date: 2021-11-09 06:17:02
Also in:
linux-devicetree, linux-leds, lkml, netdev
On 11/8/21 6:26 PM, Ansuel Smith wrote:
quoted hunk ↗ jump to hunk
diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst index cd155ead8703..645940b78d81 100644 --- a/Documentation/leds/leds-class.rst +++ b/Documentation/leds/leds-class.rst@@ -169,6 +169,34 @@ Setting the brightness to zero with brightness_set() callback function should completely turn off the LED and cancel the previously programmed hardware blinking function, if any. +Hardware driven LEDs +=================================== + +Some LEDs can be driven by hardware (for example a LED connected to +an ethernet PHY or an ethernet switch can be configured to blink on activity on +the network, which in software is done by the netdev trigger). + +To do such offloading, LED driver must support this and a supported trigger must +be used. + +LED driver should declare the correct blink_mode supported and should set the +blink_mode parameter to one of HARDWARE_CONTROLLED or SOFTWARE_HARDWARE_CONTROLLED. +The trigger will check this option and fail to activate if the blink_mode is not +supported. By default if a LED driver doesn't declare blink_mode, SOFTWARE_CONTROLLED +is assumed. + +The LED must implement 3 main API:
APIs:
+- hw_control_status(): This asks the LED driver if hardware mode is enabled + or not. Triggers will check if the hardware mode is active and will try + to offload their triggers if supported by the driver. +- hw_control_start(): This will simply enable the hardware mode for the LED. +- hw_control_stop(): This will simply disable the hardware mode for the LED. + It's advised to the driver to put the LED in the old state but this is not
for the driver
+ enforcerd and putting the LED off is also accepted.
enforced
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+ +With HARDWARE_CONTROLLED blink_mode hw_control_status/start/stop is optional +and any software only trigger will reject activation as the LED supports only +hardware mode. Known Issues ============diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig index ed800f5da7d8..bd2b19cc77ec 100644 --- a/drivers/leds/Kconfig +++ b/drivers/leds/Kconfig@@ -49,6 +49,17 @@ config LEDS_BRIGHTNESS_HW_CHANGED See Documentation/ABI/testing/sysfs-class-led for details. +config LEDS_HARDWARE_CONTROL + bool "LED Hardware Control support" + help + This option enabled Hardware control support used by leds that
enables LEDs
+ can be driven in hardware by using supported triggers. + + Hardware blink modes will be exposed by sysfs class in + /sys/class/leds based on the trigger currently active. + + If unsure, say Y.
-- ~Randy