linux-kernel - Re: [PATCH linux v1 4/4] arm: dts: Add dt-binding to support seven segment display on zaius

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Message-ID: <CACRpkdaqKDJstfypP0EL9e=TA-atiJmK9zwrBHfLmEVV8SLuAQ@mail.gmail.com>
Date:   Fri, 16 Dec 2016 00:07:36 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Arnd Bergmann <arnd@...db.de>, Mark Rutland <mark.rutland@....com>,
        Jaghathiswari Rankappagounder Natarajan <jaghu@...gle.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH linux v1 4/4] arm: dts: Add dt-binding to support seven
 segment display on zaius

On Wed, Dec 14, 2016 at 12:40 PM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:

> Looking at this more, it's a SPI driver, presumably because the first
> case where it appeared was on a SPI bus.
>
> However, it's not a SPI device as such, it's a piece of standard,
> general purpose logic that's been around for many years, pre-dating
> the SPI bus.

Indeed.

> I think a much more sensible approach would be to turn the GPIO side
> of the 74x164 driver into a library, which can be re-used by multiple
> bus-specific drivers - one for SPI which allows it to be used in its
> current form, one for our platform bus which takes the GPIO lines for
> the data, clock and clear signals.
>
> I also don't see why they shouldn't use the same compatible - they're
> the same _device_ at the end of the day, just wired up differently.
> It makes the binding documentation a little fun wrt what are required
> and optional properties, but nothing that shouldn't be too difficult.

I agree on both accounts.

Sorry for not seeing this in the first place, I was well aware that this
is a standard component and may be connected in a myriad of ways,
so I should have known better :(

Yours,
Linus Walleij