netdev - Re: [PATCH net-next 5/5] igc: Export LEDs

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Date:   Tue, 20 Jul 2021 10:54:24 +0200
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Tony Nguyen <anthony.l.nguyen@...el.com>, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org, sasha.neftin@...el.com,
        vitaly.lifshits@...el.com, vinicius.gomes@...el.com,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Dvora Fuxbrumer <dvorax.fuxbrumer@...ux.intel.com>
Subject: Re: [PATCH net-next 5/5] igc: Export LEDs

Hi Andrew,

On Mon Jul 19 2021, Andrew Lunn wrote:
> On Mon, Jul 19, 2021 at 08:06:41AM +0200, Kurt Kanzenbach wrote:
>> There are different modes such as ON, OFF, LINK established, LINK
>> activity, PAUSED ... Blinking is controlled by a different register.
>> 
>> Are there better ways to export this?
>
> As i said in another email, using LED triggers. For simple link speed
> indication, take a look at CONFIG_LED_TRIGGER_PHY. This is purely
> software, and probably not what you want.

Here's my use case/reasoning behind this patch: Upon reception of a
certain Ethernet frame, the LEDs should blink for a certain period of
time. Afterwards the default behavior should be restored. The blinking
can be done in hardware, but only for a fixed period. I needed a
different period.

Therefore, I've exported these as regular LEDs to toggle the brightness
from user space directly.

> The more complex offload of to LED control to hardware in the PHY
> subsystem it still going around and around. The basic idea is agreed,
> just not the implementation.  However, most of the implementation is
> of no help to you, since Intel drivers ignore the kernel PHY drivers
> and do their own. But the basic idea and style of user space API
> should be kept the same. So take a look at the work Marek Behún has
> been doing, e.g.
>
> https://lwn.net/Articles/830947/
>
> and a more recent version
>
> https://lore.kernel.org/netdev/20210602144439.4d20b295@dellmb/T/#m4e97c9016597fb40849c104c7c0e3bc10d5c1ff5

Thanks for the pointer.

>
> Looking at the basic idea of using LED triggers and offloading
> them. Please also try to make us of generic names for these triggers,
> so the PHY subsystem might also use the same or similar names when it
> eventually gets something merged.
>
> Please also Cc: The LED maintainers and LED list. Doing that from the
> start would of avoided this revert, since you would of get earlier
> feedback about this.

Yeah, noted.

Thanks,
Kurt

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