From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     Colin Foster <colin.foster@in-advantage.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Claudiu Manoil <claudiu.manoil@nxp.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        "UNGLinuxDriver@microchip.com" <UNGLinuxDriver@microchip.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Ioana Ciornei <ioana.ciornei@nxp.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Lars Povlsen <lars.povlsen@microchip.com>,
        Steen Hegelund <Steen.Hegelund@microchip.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: [RFC PATCH v4 net-next 00/23] add support for VSC75XX control
 over SPI
Thread-Topic: [RFC PATCH v4 net-next 00/23] add support for VSC75XX control
 over SPI
Thread-Index: AQHX2rKEbcpEShKMr0uAL3+1lm3+rawF/9+AgABI9wCAACQTgA==
Date:   Tue, 16 Nov 2021 17:41:16 +0000
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On Tue, Nov 16, 2021 at 07:32:08AM -0800, Colin Foster wrote:
> > > One thing to note: I've been following a pattern of adding "offset"
> > > variables to these drivers. I'm looking for feedback here, because I
> > > don't like it - however I feel like it is the "least bad" interface I
> > > could come up with.=20
> > >=20
> > > Specifically, ocelot has a regmap for GCB. ocelot-pinctrl would creat=
e a
> > > smaller regmap at an address of "GCB + 0x34".
> > >=20
> > > There are three options I saw here:
> > > 1. Have vsc7512_spi create a new regmap at GCB + 0x34 and pass that t=
o
> > > ocelot-pinctrl
> > > 2. Give ocelot-pinctrl the concept of a "parent bus" by which it coul=
d
> > > request a regmap.=20
> > > 3. Keep the same GCB regmap, but pass in 0x34 as an offset.
> > >=20
> > >=20
> > > I will admit that option 2 sounds very enticing, but I don't know if
> > > that type of interaction exists. If not, implementing it is probably
> > > outside the scope of a first patch set. As such, I opted for option 3=
.
> >=20
> > I think that type of interaction is called "mfd", potentially even "sys=
con".
>=20
> Before diving in, I'd come across mfd and thought that might be the
> answer. I'll reconsider it now that I have several months of staring at
> kernel code under my belt. Maybe an mfd that does SPI setup and chip
> resetting. Then I could remove all SPI code from ocelot_vsc7512_spi.

That sounds acceptable to me.=