linux-kernel - Re: [PATCH v9 03/12] mfd: simple-mfd-i2c: Save the register client data

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Date:   Tue, 10 Aug 2021 17:03:34 +1000
From:   Alistair Francis <alistair23@...il.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Alistair Francis <alistair@...stair23.me>,
        Rob Herring <robh+dt@...nel.org>, lgirdwood@...il.com,
        dl-linux-imx <linux-imx@....com>,
        Sascha Hauer <kernel@...gutronix.de>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 03/12] mfd: simple-mfd-i2c: Save the register client data

On Mon, Aug 9, 2021 at 9:14 PM Lee Jones <lee.jones@...aro.org> wrote:
>
> On Fri, 06 Aug 2021, Mark Brown wrote:
>
> > On Fri, Aug 06, 2021 at 12:38:36PM +0100, Lee Jones wrote:
> > > On Fri, 06 Aug 2021, Alistair Francis wrote:
> >
> > > > + i2c_set_clientdata(i2c, regmap);
> > > > +
> >
> > > No need to store this here.
> >
> > > Just do this in the child device:
> >
> > >      dev_get_regmap(pdev->dev.parent, NULL);
> >
> > Note that dev_get_regmap() is relatively expensive compared to a simple
> > driver data reference since it needs to go search for the device to find
> > the regmap, it's not the end of the world especially in the context of
> > doing I2C I/O but storing it isn't a terrible idea.
>
> It would be nice if someone could do some metrics on this.

I updated it to use `dev_get_regmap()` in version 10 of the series

Alistair

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