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Subject: Re: [PATCH v2 6/7] dt-bindings: net: realtek: Add property to
 configure LED mode
To:     Rob Herring <robh+dt@kernel.org>,
        Matthias Kaehlcke <mka@chromium.org>,
        Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Mark Rutland <mark.rutland@arm.com>,
        netdev <netdev@vger.kernel.org>, devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Douglas Anderson <dianders@chromium.org>
References: <20190703193724.246854-1-mka@chromium.org>
 <20190703193724.246854-6-mka@chromium.org>
 <e8fe7baf-e4e0-c713-7b93-07a3859c33c6@gmail.com>
 <20190703232331.GL250418@google.com>
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From:   Florian Fainelli <f.fainelli@gmail.com>
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Date:   Wed, 10 Jul 2019 09:28:39 -0700
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On 7/10/19 8:55 AM, Rob Herring wrote:
> On Wed, Jul 3, 2019 at 5:23 PM Matthias Kaehlcke <mka@chromium.org> wrote:
>>
>> Hi Florian,
>>
>> On Wed, Jul 03, 2019 at 02:37:47PM -0700, Florian Fainelli wrote:
>>> On 7/3/19 12:37 PM, Matthias Kaehlcke wrote:
>>>> The LED behavior of some Realtek PHYs is configurable. Add the
>>>> property 'realtek,led-modes' to specify the configuration of the
>>>> LEDs.
>>>>
>>>> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
>>>> ---
>>>> Changes in v2:
>>>> - patch added to the series
>>>> ---
>>>>  .../devicetree/bindings/net/realtek.txt         |  9 +++++++++
>>>>  include/dt-bindings/net/realtek.h               | 17 +++++++++++++++++
>>>>  2 files changed, 26 insertions(+)
>>>>  create mode 100644 include/dt-bindings/net/realtek.h
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/net/realtek.txt b/Documentation/devicetree/bindings/net/realtek.txt
>>>> index 71d386c78269..40b0d6f9ee21 100644
>>>> --- a/Documentation/devicetree/bindings/net/realtek.txt
>>>> +++ b/Documentation/devicetree/bindings/net/realtek.txt
>>>> @@ -9,6 +9,12 @@ Optional properties:
>>>>
>>>>     SSC is only available on some Realtek PHYs (e.g. RTL8211E).
>>>>
>>>> +- realtek,led-modes: LED mode configuration.
>>>> +
>>>> +   A 0..3 element vector, with each element configuring the operating
>>>> +   mode of an LED. Omitted LEDs are turned off. Allowed values are
>>>> +   defined in "include/dt-bindings/net/realtek.h".
>>>
>>> This should probably be made more general and we should define LED modes
>>> that makes sense regardless of the PHY device, introduce a set of
>>> generic functions for validating and then add new function pointer for
>>> setting the LED configuration to the PHY driver. This would allow to be
>>> more future proof where each PHY driver could expose standard LEDs class
>>> devices to user-space, and it would also allow facilities like: ethtool
>>> -p to plug into that.
>>>
>>> Right now, each driver invents its own way of configuring LEDs, that
>>> does not scale, and there is not really a good reason for that other
>>> than reviewing drivers in isolation and therefore making it harder to
>>> extract the commonality. Yes, I realize that since you are the latest
>>> person submitting something in that area, you are being selected :)
> 
> I agree.
> 
>> I see the merit of your proposal to come up with a generic mechanism
>> to configure Ethernet LEDs, however I can't justify spending much of
>> my work time on this. If it is deemed useful I'm happy to send another
>> version of the current patchset that addresses the reviewer's comments,
>> but if the implementation of a generic LED configuration interface is
>> a requirement I will have to abandon at least the LED configuration
>> part of this series.
> 
> Can you at least define a common binding for this. Maybe that's just
> removing 'realtek'. While the kernel side can evolve to a common
> infrastructure, the DT bindings can't.

That would be a great start, and that is actually what I had in mind
(should have been more specific), I was not going to have you Matthias
do the grand slam and convert all this LED configuration into the LEDs
class etc. that would not be fair.

It seems to be that we can fairly easily agree on a common binding for
LED configuration, I would define something along those lines to be
flexible:

phy-led-configuration = <LED_NUM_MASK LED_CFG_MASK>;

where LED_NUM_MASK is one of:

0 -> link
1 -> activity
2 -> speed

that way you can define single/dual/triple LED configurations by
updating the bitmask.

LED_CFG_MASK is one of:

0 -> LED_CFG_10
1 -> LED_CFG_100
2 -> LED_CFG_1000

(let's assume 1Gbps or less for now)

or this can be combined in a single cell with a left shift.

Andrew, Heiner, do you see that approach working correctly and scaling
appropriately?
-- 
Florian