Re: [PATCH v5 1/8] leds: add support for hardware driven LEDs
From: Randy Dunlap <hidden>
Date: 2021-11-13 01:04:25
Also in:
linux-devicetree, linux-leds, lkml, netdev
On 11/12/21 7:35 AM, Ansuel Smith wrote:
quoted hunk ↗ jump to hunk
diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst index cd155ead8703..e5d266919a19 100644 --- a/Documentation/leds/leds-class.rst +++ b/Documentation/leds/leds-class.rst@@ -169,6 +169,38 @@ 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 an 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 control mode supported and should set +the LED_SOFTWARE_CONTROLLED or LED_HARDWARE_CONTROLLED bit in the flags +parameter. +The trigger will check these bits and fail to activate if the control mode +is not supported. By default if a LED driver doesn't declare a control mode,
if an LED driver
+bit LED_SOFTWARE_CONTROLLED is assumed and set. + +The LED must implement 3 main APIs: +- hw_control_status(): This asks the LED driver if hardware mode is enabled + or not. +- hw_control_start(): This will simply enable the hardware mode for the LED + and the LED driver should reset any active blink_mode. +- 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 + enforced and putting the LED off is also accepted. + +If LED_HARDWARE_CONTROLLED bit is the only control mode set (LED_SOFTWARE_CONTROLLED +not set) set hw_control_status/start/stop is optional as the LED supports only
^^^ is that an extra "set"? I can't quite read this sentence.
And it would be better with a comma added, like so:
not set),
+hardware mode and any software only trigger will reject activation.
software-only
+ +On init an LED driver that support a hardware mode should reset every blink mode
supports
+set by default.
-- ~Randy