Subject: Re: [RFC PATCH v4 2/8] leds: document additional use of blink_set for
 hardware control
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,
        =?UTF-8?Q?Marek_Beh=c3=ban?= <kabel@kernel.org>
References: <20211111013500.13882-1-ansuelsmth@gmail.com>
 <20211111013500.13882-3-ansuelsmth@gmail.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <3c37f8c8-5c0a-302c-e68c-e6ac37cde695@infradead.org>
Date:   Wed, 10 Nov 2021 18:28:09 -0800
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Hi Ansuel,

Sorry -- I screwed this one up a little bit on the previous iteration.

On 11/10/21 5:34 PM, Ansuel Smith wrote:
> diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
> index 0175954717a3..c06a18b811de 100644
> --- a/Documentation/leds/leds-class.rst
> +++ b/Documentation/leds/leds-class.rst
> @@ -202,6 +202,23 @@ hardware mode and any software only trigger will reject activation.
>   On init a LED driver that support a hardware mode should reset every blink mode
>   set by default.
>   
> +Once a trigger has declared support for hardware-controller blinks, it will use

                                            hardware-controlled

> +blink_set() to try to offload his trigger on activation/configuration.
> +blink_set() will return 0 if the requested modes set in trigger_data can be
> +controlled by hardware or an error if both the mode bitmap is not supported by

maybe:                                if both of the bitmap modes are not supported by

> +the hardware or there was a problem in the configuration.
> +
> +Following blink_set logic, setting brightness to LED_OFF with hardware control active
> +will reset any active blink mode and disable hardware control setting the LED to off.
> +
> +It's in the LED driver's interest to know how to elaborate the trigger data and report support
> +for a particular set of blink modes. For this exact reason explicit support for the specific
> +trigger is mandatory or the driver returns -EOPNOTSUPP if asked to enter hardware 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 hardware blink modes or doesn't know

                                                                    mode

> +how to handle the provided trigger data.


thanks.
-- 
~Randy