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

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Date:   Thu, 12 May 2022 08:03:56 -0700
From:   Colin Foster <colin.foster@...advantage.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Vladimir Oltean <vladimir.oltean@....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 Thu, May 12, 2022 at 10:49:39AM +0100, Lee Jones wrote:
> On Tue, 10 May 2022, Colin Foster wrote:
> 
> > On Tue, May 10, 2022 at 04:32:26PM +0100, Lee Jones wrote:
> > > 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]
> > 
> > I see your point. This wasn't always the case, since ocelot-core prior
> > to v8 would call ocelot_spi_devm_init_regmap. Since this was changed,
> > the "dev, dev" part can all be handled internally. That's nice.
> > 
> > > 
> > > 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;
> > > }
> > 
> > If I do this, won't I have to declare ocelot_spi_devm_init_regmap in a
> > larger scope (include/soc/mscc/ocelot.h)? I like the idea of keeping it
> > more hidden inside drivers/mfd/ocelot.h, assuming I can't keep it
> > enclosed in drivers/mfd/ocelot-spi.c entirely.
> 
> Yes, it will have the same scope as ocelot_init_regmap_from_resource().
> 
> Have you considered include/linux/mfd?

I hadn't, but that seems to make sense here. I'll try to get all the
suggestions implemented in the next few days and send something back
out.

Thanks for the feedback!

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