linux-kernel - Re: [PATCH v2 2/5] MFD: RK808: Add new mfd driver for RK808

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Date:	Wed, 27 Aug 2014 12:27:09 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Chris Zhong <zyw@...k-chips.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	sameo@...ux.intel.com, lgirdwood@...il.com, broonie@...nel.org,
	a.zummo@...ertech.it, mturquette@...aro.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	rtc-linux@...glegroups.com, grant.likely@...aro.org,
	hl@...k-chips.com, huangtao@...k-chips.com, cf@...k-chips.com,
	zhangqing@...k-chips.com, xxx@...k-chips.com,
	dianders@...omium.org, heiko@...ech.de, olof@...om.net,
	sonnyrao@...omium.org, dtor@...omium.org,
	javier.martinez@...labora.co.uk, kever.yang@...k-chips.com
Subject: Re: [PATCH v2 2/5] MFD: RK808: Add new mfd driver for RK808

On Tue, 26 Aug 2014, Dmitry Torokhov wrote:
> On Tue, Aug 26, 2014 at 10:22:05AM +0100, Lee Jones wrote:
> > On Mon, 25 Aug 2014, Chris Zhong wrote:
> > > On 08/20/2014 05:21 PM, Lee Jones wrote:
> > > >On Wed, 20 Aug 2014, Chris Zhong wrote:
> > > >
> > > >>The RK808 chip is a power management IC for multimedia and handheld
> > > >>devices. It contains the following components:
> > > >>
> > > >>- Regulators
> > > >>- RTC
> > > >>
> > > >>The rk808 core driver is registered as a platform driver and provides
> > > >>communication through I2C with the host device for the different
> > > >>components.
> > > >>
> > > >>Signed-off-by: Chris Zhong <zyw@...k-chips.com>
> > > >>---
> > 
> > [...]
> > 
> > > >>+	rk808->pdata = pdata;
> > > >Remove pdata from 'struct rk808'.  You can obtain it from dev.
> > > 
> > > Can I keep this pdata in rk808, because it is used in the regulator driver.
> > > The one obtain from dev maybe empty.
> > 
> > If the one in dev is empty, you should populate that instead.
> 
> No, drivers should not populate platform data in devices - they do not
> own it (unlike drvdata). Platform data should be read-only so that if
> one would unbind and then try to re-bind the driver we'd end up in
> exactly same state as before.

Right.

I guess this point is moot now, as my other point about pdata not
actually being required has been accecpted.  But, when I say "you
can obtain it from dev" I meant via dev_get_platdata(dev), rather than
dev_get_platdata(dev->parent).  So if this 'pdata' has to go somewhere,
rather than sticking it in the MFD's (parent) platform_data, the
.platform_data attribute in 'struct mfd_cell' should be used.

> For DT systems we should be allocating platform data separately and make
> sure we clean up after ourselves.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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