Re: [RFC PATCH v3 2/8] leds: add function to configure hardware controlled LED

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, "Marek Behún" <kabel@kernel.org>
Subject: Re: [RFC PATCH v3 2/8] leds: add function to configure hardware controlled LED
Date: Mon, 8 Nov 2021 22:12:05 -0800	[thread overview]
Message-ID: <3e854c1c-25e2-789b-de67-d99344fcb498@infradead.org> (raw)
In-Reply-To: <20211109022608.11109-3-ansuelsmth@gmail.com>

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 645940b78d81..efd2f68c46a7 100644
> --- a/Documentation/leds/leds-class.rst
> +++ b/Documentation/leds/leds-class.rst
> @@ -198,6 +198,31 @@ 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.
>   
> +A trigger once he declared support for hardware controlled blinks, will use the function

Maybe this:
    Once a trigger has declared support for hardware-controller blinks, it will us the function

> +hw_control_configure() provided by the driver to check support for a particular blink mode.
> +This function passes as the first argument (flag) a u32 flag.
> +The second argument (cmd) of hw_control_configure() method can be used to do various
> +operations for the specific blink mode. We currently support ENABLE, DISABLE, READ, ZERO
> +and SUPPORTED to enable, disable, read the state of the blink mode, ask the LED
> +driver if it does supports the specific blink mode and to reset any blink mode active.
> +
> +In ENABLE/DISABLE hw_control_configure() should configure the LED to enable/disable the
> +requested blink mode (flag).
> +In READ hw_control_configure() should return 0 or 1 based on the status of the requested
> +blink mode (flag).
> +In SUPPORTED hw_control_configure() should return 0 or 1 if the LED driver supports the
> +requested blink mode (flags) or not.
> +In ZERO hw_control_configure() should return 0 with success operation or error.
> +
> +The unsigned long flag is specific to the trigger and change across them. It's in the LED

                                                          changes

> +driver interest know how to elaborate this flag and to declare support for a

    driver's interest to know how to

> +particular trigger. For this exact reason explicit support for the specific
> +trigger is mandatory or the driver returns -EOPNOTSUPP if asked to enter offload mode
> +with a not supported trigger.
> +If the driver returns -EOPNOTSUPP on hw_control_configure(), the trigger activation will
> +fail as the driver doesn't support that specific offload trigger or doesn't know
> +how to handle the provided flags.


-- 
~Randy