linux-kernel - Re: [RFC PATCH 3/3] gpio: ej1x8: Add GPIO driver for Etron Tech Inc. EJ168/EJ188/EJ198

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Date:   Thu, 31 Dec 2020 01:15:08 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     linux-usb <linux-usb@...r.kernel.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>,
        Rob Herring <robh+dt@...nel.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 3/3] gpio: ej1x8: Add GPIO driver for Etron Tech Inc. EJ168/EJ188/EJ198

Hi Linus,

On Mon, Dec 21, 2020 at 4:28 PM Martin Blumenstingl
<martin.blumenstingl@...glemail.com> wrote:
>
> Hi Linus,
>
> On Wed, Oct 7, 2020 at 9:44 PM Martin Blumenstingl
> <martin.blumenstingl@...glemail.com> wrote:
> [...]
> > > As noted on the earlier patches I think this should be folded into the
> > > existing XHCI USB driver in drivers/usb/host/xhci-pci.c or, if that
> > > gets messy, as a separate bolt-on, something like
> > > xhci-pci-gpio.[c|h] in the drivers/usb/host/* directory.
> > > You can use a Kconfig symbol for the GPIO portions or not.
> > OK, I will do that if there are no objections from other developers
> > I am intending to place the relevant code in xhci-pci-etron.c, similar
> > to what we already have with xhci-pci-renesas.c
> I tried this and unfortunately there's a catch.
> the nice thing about having a separate GPIO driver means that the
> xhci-pci driver doesn't need to know about it.
>
> I implemented xhci-pci-etron.c and gave it a Kconfig option.
> xhci-pci is then calling into xhci-pci-etron (through some
> etron_xhci_pci_probe function).
> unfortunately this means that xhci-pci now depends on xhci-pci-etron.
> for xhci-pci-renesas this is fine (I think) because that part of the
> code is needed to get the xHCI controller going
> but for xhci-pci-etron this is a different story: the GPIO controller
> is entirely optional and only used on few devices
>
> my goal is (at some point in the future) to have the GPIO driver in OpenWrt.
> I am not sure if they would accept a patch where xhci-pci would then
> pull in the dependencies for that Etron controller, even though most
> boards don't need it.
>
> Please let me know if you have any idea on how to solve this.
next week I have some free time to work on this
I am still interested in any ideas that you have about this


Best regards,
Martin