netdev - Re: [RFC PATCH v3 1/8] leds: add support for hardware driven LEDs

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Message-ID: <YYrc1UfhVLEO/Nth@Ansuel-xps.localdomain>
Date:   Tue, 9 Nov 2021 21:40:53 +0100
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     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: [RFC PATCH v3 1/8] leds: add support for hardware driven LEDs

On Tue, Nov 09, 2021 at 09:34:23PM +0100, Andrew Lunn wrote:
> On Tue, Nov 09, 2021 at 03:26:01AM +0100, Ansuel Smith wrote:
> > Some LEDs can be driven by hardware (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 supported
> > trigger must be used.
> > 
> > LED driver should declare the correct blink_mode supported and should set
> > the blink_mode parameter to one of HARDWARE_CONTROLLED or
> > SOFTWARE_HARDWARE_CONTROLLED.
> > The trigger will check this option and fail to activate if the blink_mode
> > is not supported. By default if a LED driver doesn't declare blink_mode,
> > SOFTWARE_CONTROLLED is assumed.
> > 
> > The LED must implement 3 main API:
> > - trigger_offload_status(): This asks the LED driver if offload mode is
> >     enabled or not.
> >     Triggers will check if the offload mode is supported and will be
> >     activated accordingly. If the trigger can't run in software mode,
> >     return -EOPNOTSUPP as the blinking can't be simulated by software.
> 
> I don't understand this last part. The LED controller is not
> implementing software mode, other than providing a method to manually
> turn the LED on and off. And there is a well defined call for that. If
> that call is a NULL, it is clear it is not implemented. There is no
> need to ask the driver.
> 
>      Andrew

You are right I have to remove the last part as it doesn't make sense.
We already use blink_mode. Will remove in v4.

-- 
	Ansuel