linux-kernel - Re: [RFC PATCH 2/3] dt-bindings: gpio: Add binding documentation for Etron EJ168/EJ188/EJ198

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Message-ID: <CAFBinCBpDn1Vx1ZQdk-Gf-muuAyxjXb+zCkvW6jsH8jP6mDuTw@mail.gmail.com>
Date:   Fri, 16 Oct 2020 22:52:44 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [RFC PATCH 2/3] dt-bindings: gpio: Add binding documentation for
 Etron EJ168/EJ188/EJ198

Hi Linus,

On Wed, Oct 14, 2020 at 2:43 PM Rob Herring <robh+dt@...nel.org> wrote:
>
> On Tue, Oct 13, 2020 at 8:27 AM Linus Walleij <linus.walleij@...aro.org> wrote:
> >
> > On Wed, Oct 7, 2020 at 9:58 PM Martin Blumenstingl
> > <martin.blumenstingl@...glemail.com> wrote:
> > > On Wed, Oct 7, 2020 at 11:19 AM Linus Walleij <linus.walleij@...aro.org> wrote:
> > > > On Sun, Oct 4, 2020 at 8:00 PM Martin Blumenstingl
> > > > <martin.blumenstingl@...glemail.com> wrote:
> > > >
> > > > > +properties:
> > > > > +  compatible:
> > > > > +    enum:
> > > > > +      - pci1b6f,7023
> > > > > +      - pci1b6f,7052
> > > >
> > > > I think it is better to let the PCI driver for the whole hardware in
> > > > drivers/usb/host/xhci-pci.c probe from the PCI configuration space
> > > > numbers, and then add a gpio_chip to xhci-pci.c.
> > >
> > > to have everything consistent I will move the binding to
> > > Documentation/devicetree/bindings/usb
> >
> > I do not understand why a PCI device would need a DT binding
> > at all. They just probe from the magic number in the PCI
> > config space, they spawn struct pci_dev PCI devices, not the
> > type of platform devices coming out of the DT parser code.
> > No DT compatible needed.
>
> Same reason for all the discoverable buses need bindings. There can be
> parts that are not discoverable or connections with non-discoverable
> nodes. There's also cases where the discoverable device has to be
> powered, reset deasserted, clocks enabled, etc. first to be
> discovered.
>
> If the GPIOs here had connections elsewhere in the DT, then we have to
> describe the provider in DT.
this is exactly what I need it for: that platform has hand-written
.dts files and I need to wire up a GPIO LED


Best regards,
Martin