linux-kernel - Re: [PATCH v5 2/8] leds: document additional use of blink

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Message-ID: <5ef01f7d-b250-73e5-3f06-d03aba1304c7@infradead.org>
Date:   Fri, 12 Nov 2021 16:55:58 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Ansuel Smith <ansuelsmth@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jonathan Corbet <corbet@....net>, Pavel Machek <pavel@....cz>,
        John Crispin <john@...ozen.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-leds@...r.kernel.org,
        Marek Behún <kabel@...nel.org>
Subject: Re: [PATCH v5 2/8] leds: document additional use of blink_set for
 hardware control

On 11/12/21 7:35 AM, Ansuel Smith wrote:
> diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
> index e5d266919a19..fa6e1cfc4628 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 an LED driver that support a hardware mode should reset every blink mode
>   set by default.
>   
> +Once a trigger has declared support for hardware-controlled blinks, it will use
> +blink_set() to try to offload his trigger on activation/configuration.

                                  this trigger

> +blink_set() will return 0 if the requested modes set in trigger_data can be
> +controlled by hardware or an error 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 mode or doesn't know
> +how to handle the provided trigger data.


-- 
~Randy