Re: [RFC PATCH v2 1/5] leds: trigger: add API for HW offloading of triggers

From: "Marek Behún" <kabel@kernel.org>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Ansuel Smith <ansuelsmth@gmail.com>,
	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
Subject: Re: [RFC PATCH v2 1/5] leds: trigger: add API for HW offloading of triggers
Date: Mon, 8 Nov 2021 18:56:37 +0100	[thread overview]
Message-ID: <20211108185637.21b63d40@thinkpad> (raw)
In-Reply-To: <YYliclrZuxG/laIh@lunn.ch>

On Mon, 8 Nov 2021 18:46:26 +0100
Andrew Lunn <andrew@lunn.ch> wrote:

> > Dear Ansuel,
> > 
> > what is the purpose of adding trigger_offload() methods to LED, if you
> > are not going to add support to offload the netdev trigger? That was
> > the entire purpose when I wrote that patch.
> > 
> > If you just want to create a new trigger that will make the PHY chip do
> > the blinking, there is no need at all for the offloading patch.
> > 
> > And you will also get a NACK from me and also Pavel (LED subsystem
> > maintainer).
> > 
> > The current plan is to:
> > - add support for offloading existing LED triggers to HW (LED
> >   controllers (PHY chips, for example))
> > - make netdev trigger try offloading itself to HW via this new API (if
> >   it fails, netdev trigger will blink the LED in SW as it does now)
> > - create LED classdevices in a PHY driver that have the offload()
> >   methods implemented. The offload method looks at what trigger is
> >   being enabled for the LED, and it if it is a netdev trigger with such
> >   settings that are possible to offload, it will be offloaded.
> > 
> >   This whole thing makes use of the existing sysfs ABI.
> >   So for example if I do
> >     cd /sys/class/net/eth0/phydev/leds/<LED>
> >     echo netdev >trigger
> >     echo eth0 >device_name
> >     echo 1 >rx
> >     echo 1 >tx
> >   The netdev trigger is activated, and it calls the offload() method.
> >   The offload() method is implemented in the PHY driver, and it checks
> >   that it can offload these settings (blink on rx/tx), and will enable
> >   this.
> > - extend netdev trigger to support more settings:
> >   - indicate link for specific link modes only (for example 1g, 100m)
> >   - ...
> > - extend PHY drivers to support offloading of these new settings
> > 
> > Marek  
> 
> Hi Marek
> 
> The problem here is, you are not making much progress. People are
> giving up on you ever getting this done, and doing their own
> implementation. Ansuel code is not mature enough yet, it has problems,
> but he is responsive, he is dealing with comments, progress is being
> made. At some point, it is going to be good enough, and it will get
> merged, unless you actual get your code to a point it can be merged.
> 
> 	Andrew

Hello Andrew,

you are right that this has been taking too long on my side. I am sorry
for that.

I guess I will have to work on this again ASAP or we will end up with
solution that I don't like.

Nonetheless, what is your opinion about offloading netdev trigger vs
introducing another trigger?

Marek