Messages in this thread | | | Subject | Re: [RFC PATCH v3 1/8] leds: add support for hardware driven LEDs | From | Randy Dunlap <> | Date | Mon, 8 Nov 2021 22:16:51 -0800 |
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On 11/8/21 6:26 PM, Ansuel Smith wrote: > 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
> + > +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
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