linux-kernel - Re: [PATCH 12/19] twl4030: mfd_cell is now implicitly available to drivers

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Message-ID: <20110202223959.244b4a01@queued.net>
Date:	Wed, 2 Feb 2011 22:39:59 -0800
From:	Andres Salomon <dilinger@...ued.net>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>, linux-kernel@...r.kernel.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Peter Ujfalusi <peter.ujfalusi@...ia.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Timur Tabi <timur@...escale.com>, linux-input@...r.kernel.org,
	alsa-devel@...a-project.org
Subject: Re: [PATCH 12/19] twl4030: mfd_cell is now implicitly available to
 drivers

On Wed, 2 Feb 2011 22:05:21 -0800
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:

> On Wed, Feb 02, 2011 at 08:15:22PM -0800, Andres Salomon wrote:
> >  static int __devinit twl4030_vibra_probe(struct platform_device
> > *pdev) {
> > -	struct twl4030_codec_vibra_data *pdata =
> > pdev->dev.platform_data;
> > +	struct twl4030_codec_vibra_data *pdata =
> > platform_get_drvdata(pdev);
> 
> No, device's drvdata belongs to _this_ driver, and it is supposed to
> manage it and use as it sees fit.

Right, so it's used to pass data to the probe function; once the probe
function has obtained the pdata pointer, it's free to do with it what
it will.


> 
> Note platform_set_drvdata(pdev, info) later in this function along
> with platform_set_drvdata(pdev, NULL) in twl4030_vibra_remove(),
> which means that with your change you will be able to bind the device
> only once.
> 

Hm, good point; if the driver is reloaded, the pdev that was created by
mfd-core will have lost the pointer to pdata.

I wonder if I should be using mfd's driver_data instead. I used
platform_data because a bunch of drivers had already made use of it to
pass cell information..
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