linux-kernel - Re: [PATCH net-next 1/4] dt-bindings: net: dsa: realtek: describe LED usage

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Date: Thu, 21 Mar 2024 09:03:34 -0300
From: Luiz Angelo Daros de Luca <luizluca@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Linus Walleij <linus.walleij@...aro.org>, Alvin Šipraga <alsi@...g-olufsen.dk>, 
	Florian Fainelli <f.fainelli@...il.com>, Vladimir Oltean <olteanv@...il.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH net-next 1/4] dt-bindings: net: dsa: realtek: describe LED usage

Hi Andrew,

Em dom., 10 de mar. de 2024 às 15:02, Andrew Lunn <andrew@...n.ch> escreveu:
>> On Sun, Mar 10, 2024 at 01:51:58AM -0300, Luiz Angelo Daros de Luca wrote:
> > Each port can have up to 4 LEDs (3 for current rtl8365mb devices). The
> > LED reg property will indicate its LED group.
> > +                properties:
> > +                  reg:
> > +                    description:
> > +                      "reg indicates the LED group for this LED"
> > +                    enum: [0, 1, 2, 3]
>
> If this identifies the group, what identifies the actual LED? There
> are four of them. How do i say LEDs 0 and 1 are unused, 2 and 3 are
> wired to LEDs?

Do we need to mention a specific HW is not present? I guess we just
omit it, like the led@1 and led@2 in the example.

> It would be much more usual for reg to be the LED number for the
> port. And there then be a group property indicating what group the LED
> belongs to. However, i'm wondering, is group fixed? Do we actually
> need it in DT, or can there just be a table in the driver which maps
> port:led to group?

The LED groups are a fixed HW feature. The chip has dedicated pins for
each LED in each group. Those pins might have an alternative usage (as
an GPIO) but you cannot change a LED from a group to another in SW.
That's why I thought it was a thing to be described in the DT.

>          Andrew

Regards,

Luiz