netdev - Re: [PATCH] leds: trigger: netdev: skip setting baseline state in activate if hw-controlled

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Date: Wed, 6 Dec 2023 18:45:31 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Heiner Kallweit <hkallweit1@...il.com>
Cc: Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
	Christian Marangi <ansuelsmth@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] leds: trigger: netdev: skip setting baseline state in
 activate if hw-controlled

> >> I actually think we need to define some best practices, ordered on
> >> what the hardware can do.
> >>
> >> 1) With software control, set_brightness should do what you expect,
> >> not return an error.
> >>
> >> 2) Without full software control, but there is a mechanism to report a
> >> problem, like constant blinking, or off, do that, and return
> >> -EOPNOTSUPP.
> >>
> >> 3) Really dumb hardware like this, set_brightness should be a NULL
> >> pointer. The core returns -EOPNOTSUPP.
> >>
> >> The core should return this -EOPNOTSUPP to user space, but it should
> >> accept the configuration change. So the user can put it into an
> >> invalid state, in order to get to a valid state with further
> >> configuration.
> >>
> > Sounds good to me. Let me come up with a RFC patch.
> > 
> >> I don't see an easy way to let the user know what the valid states
> >> are. We currently have a 10bit state. I don't think we can put all the
> >> valid ones in a /sysfs file, especially when QCA8K pretty much
> >> supports everything.
> >>
> >> 	 Andrew
> > 
> > Heiner
> 
> Patch is so simple that I send it this way. What do you think?

That is simpler than i expected.

But i think we need to document our expectations. What do we expect an
LED driver to do when it cannot support software blinking. So please
could you add a comment somewhere. Maybe extend the

/*
 *Configurable sysfs attributes:
 *

section?

Thanks
	Andrew