Re: [RFC PATCH 1/6] leds: trigger: add API for HW offloading of triggers
From: Randy Dunlap <hidden>
Date: 2021-11-07 22:52:42
Also in:
linux-doc, linux-leds, lkml, netdev
Hi, On 11/7/21 9:57 AM, Ansuel Smith wrote:
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From: Marek Behún <kabel@kernel.org> Add method trigger_offload() and member variable `offloaded` to struct led_classdev. Add helper functions led_trigger_offload() and led_trigger_offload_stop(). The trigger_offload() method, when implemented by the LED driver, should be called (via led_trigger_offload() function) from trigger code wanting to be offloaded at the moment when configuration of the trigger changes. If the trigger is successfully offloaded, this method returns 0 and the trigger does not have to blink the LED in software. If the trigger with given configuration cannot be offloaded, the method should return -EOPNOTSUPP, in which case the trigger must blink the LED in SW. The second argument to trigger_offload() being false means that the offloading is being disabled. In this case the function must return 0, errors are not permitted. An additional config CONFIG_LEDS_OFFLOAD_TRIGGERS is added to add support for these special trigger offload driven. Signed-off-by: Marek Behún <kabel@kernel.org> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com> --- Documentation/leds/leds-class.rst | 22 +++++++++++++++++++++ drivers/leds/led-triggers.c | 1 + drivers/leds/trigger/Kconfig | 10 ++++++++++ include/linux/leds.h | 33 +++++++++++++++++++++++++++++++ 4 files changed, 66 insertions(+)diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst index cd155ead8703..035a738afc4a 100644 --- a/Documentation/leds/leds-class.rst +++ b/Documentation/leds/leds-class.rst@@ -169,6 +169,28 @@ 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 offloading of LED triggers +=================================== + +Some LEDs can offload SW triggers to hardware (for example a LED connected to
Better to s/SW/software/ and s/HW/hardware/ throughout the documentation file and Kconfig file(s).
+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 the this and a deficated offload
drop: the dedicated
+trigger must be used. The LED must implement the trigger_offload() method and
How does an LED implement the trigger_offload() method? They don't have very much logic in them AFAIK.
+the trigger code must try to call this method (via led_trigger_offload() +function) when configuration of the trigger (trigger_data) changes. + +The implementation of the trigger_offload() method by the LED driver must return +0 if the offload is successful and -EOPNOTSUPP if the requested trigger +configuration is not supported and the trigger should be executed in software. +If trigger_offload() returns negative value, the triggering will be done in +software, so any active offloading must also be disabled. + +If the second argument (enable) to the trigger_offload() method is false, any +active HW offloading must be deactivated. In this case errors are not permitted +in the trigger_offload() method.
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diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig index dc6816d36d06..c073e64e0a37 100644 --- a/drivers/leds/trigger/Kconfig +++ b/drivers/leds/trigger/Kconfig@@ -9,6 +9,16 @@ menuconfig LEDS_TRIGGERS if LEDS_TRIGGERS +config LEDS_OFFLOAD_TRIGGERS + bool "LED Offload Trigger support" + help + This option enabled offload triggers support used by leds that
LEDs
+ can be driven in HW by declaring some specific triggers. + A offload trigger will expose a sysfs dir to configure the + different blinking trigger and the available hw trigger.
Are the sysfs file values/meanings documented here? I seem to have missed them.
+ + If unsure, say Y. +
thanks. -- ~Randy