netdev - Re: [RFC v8 net-next 08/16] mfd: ocelot: add support for the vsc7512 chip via spi

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Message-ID: <YnqFijExn8Nn+xhs@google.com>
Date:   Tue, 10 May 2022 16:32:26 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     Colin Foster <colin.foster@...advantage.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Terry Bowman <terry.bowman@....com>,
        Wolfram Sang <wsa@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Manoil <claudiu.manoil@....com>
Subject: Re: [RFC v8 net-next 08/16] mfd: ocelot: add support for the vsc7512
 chip via spi

On Mon, 09 May 2022, Vladimir Oltean wrote:

> On Mon, May 09, 2022 at 04:49:22PM -0700, Colin Foster wrote:
> > > > +struct regmap *ocelot_init_regmap_from_resource(struct device *child,
> > > > +						const struct resource *res)
> > > > +{
> > > > +	struct device *dev = child->parent;
> > > > +
> > > > +	return ocelot_spi_devm_init_regmap(dev, child, res);
> > > 
> > > So much for being bus-agnostic :-/
> > > Maybe get the struct ocelot_ddata and call ocelot_spi_devm_init_regmap()
> > > via a function pointer which is populated by ocelot-spi.c? If you do
> > > that don't forget to clean up drivers/mfd/ocelot.h of SPI specific stuff.
> > 
> > That was my initial design. "core" was calling into "spi" exclusively
> > via function pointers.
> > 
> > The request was "Please find a clearer way to do this without function
> > pointers"
> > 
> > https://lore.kernel.org/netdev/Ydwju35sN9QJqJ%2FP@google.com/
> 
> Yeah, I'm not sure what Lee was looking for, either. In any case I agree
> with the comment that you aren't configuring a bus. In this context it
> seems more appropriate to call this function pointer "init_regmap", with
> different implementations per transport.

FWIW, I'm still against using function pointers for this.

What about making ocelot_init_regmap_from_resource() an inline
function and pushing it into one of the header files?

[As an aside, you don't need to pass both dev (parent) and child]

In there you could simply do:

inline struct regmap *ocelot_init_regmap_from_resource(struct device *dev,
						       const struct resource *res)
{
	if (dev_get_drvdata(dev->parent)->spi)
		return ocelot_spi_devm_init_regmap(dev, res);

	return NULL;
}

Also, do you really need devm in the title?

> Or alternatively you could leave the "core"/"spi" pseudo-separation up
> to the next person who needs to add support for some other register I/O
> method.

Or this.  Your call.

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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