Re: [RFC PATCH v2 1/5] leds: trigger: add API for HW offloading of triggers

From: Randy Dunlap <rdunlap@infradead.org>
To: Ansuel Smith <ansuelsmth@gmail.com>, Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Vladimir Oltean <olteanv@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>, Pavel Machek <pavel@ucw.cz>,
	John Crispin <john@phrozen.org>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-leds@vger.kernel.org
Cc: "Marek Behún" <kabel@kernel.org>
Subject: Re: [RFC PATCH v2 1/5] leds: trigger: add API for HW offloading of triggers
Date: Sun, 7 Nov 2021 18:29:05 -0800	[thread overview]
Message-ID: <7e73d616-9326-ff03-639f-b3b264e64a26@infradead.org> (raw)
In-Reply-To: <20211108002500.19115-2-ansuelsmth@gmail.com>

On 11/7/21 4:24 PM, Ansuel Smith wrote:
> From: Marek Behún <kabel@kernel.org>
> 

> ---
>   Documentation/leds/leds-class.rst | 20 +++++++++++++++++++
>   drivers/leds/led-triggers.c       |  1 +
>   drivers/leds/trigger/Kconfig      | 10 ++++++++++
>   include/linux/leds.h              | 33 +++++++++++++++++++++++++++++++
>   4 files changed, 64 insertions(+)
> 
> diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
> index cd155ead8703..5bf6e5d471ce 100644
> --- a/Documentation/leds/leds-class.rst
> +++ b/Documentation/leds/leds-class.rst
> @@ -169,6 +169,26 @@ 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 be driven by hardware triggers (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 deficated offload

                                                              dedicated

> +trigger must be used. The LED must implement the trigger_offload() method and
> +the trigger code must try to call this method (via led_trigger_offload()
> +function) to set the LED to this particular mode. (and disable any software
> +blinking)
> +
> +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.
> +
> +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

Preferably s/HW/hardware/ and s/SW/software/ throughout documentation and Kconfig
files.

> +in the trigger_offload() method and the driver will be set to the new trigger.
>   
>   Known Issues
>   ============

> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
> index dc6816d36d06..33aba8defeab 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

	              enables                                  LEDs

> +	  can be driven in hardware by declaring some specific triggers.
> +	  A offload trigger will expose a sysfs dir to configure the
> +	  different blinking trigger and the available hardware triggers.
> +
> +	  If unsure, say Y.

-- 
~Randy