linux-kernel - Re: [PATCH 07/12] mfd: syscon: Consider platform data a regmap config name

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Message-ID: <1392203209.3380.57.camel@hornet>
Date:	Wed, 12 Feb 2014 11:06:49 +0000
From:	Pawel Moll <pawel.moll@....com>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Alexander Shiyan <shc_work@...l.ru>,
	"arm@...nel.org" <arm@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>
Subject: Re: [PATCH 07/12] mfd: syscon: Consider platform data a regmap
 config name

On Wed, 2014-02-12 at 08:26 +0000, Lee Jones wrote:
> > > Use the device platform data as a regmap config
> > > name. This is particularly useful in the regmap
> > > debugfs when there is more than one syscon device
> > > registered, to distinguish the register blocks.
> > > 
> > > Cc: Samuel Ortiz <sameo@...ux.intel.com>
> > > Cc: Lee Jones <lee.jones@...aro.org>
> > > Signed-off-by: Pawel Moll <pawel.moll@....com>
> > > ---
> > ...
> > > syscon_regmap_config.max_register = res->end - res->start - 3;
> > > +	syscon_regmap_config.name = dev_get_platdata(&pdev->dev);
> > 
> > Is dev_name(&pdev->dev) can be used for such purpose?
> 
> Yes of course.
> 
> Either use the automatically generated name or over-ride with
> dev->init_name prior to registration or call dev_set_name()
> manually. Then retrieve with Alexander's suggestion.
> 
> Is there any technical reason why this is not possible with your
> implementation?

Hold on, guys. Let me just point out that we're talking "non-DT"
platform devices here (either statically defined struct
platform_device-s or - my case - the MFD cells).

In this case device/driver matching relies completely on device name.
Either the pdev->name must be identical (strcmp) to pdrv->name, or the
pdev->name must be identical (strcmp again) to one of the pdev->id_table
entries. See platform_match() in driver/base/platform.c for more
details.

Therefore the dev_name(&pdev->dev) on a non-DT-originating sysconf
devince will always return "sysconf.*", unless you're ready to maintain
a growing syscon_ids[] list. If so, I will have to add three entries
there ("sys_id", "sys_misc" and "sys_procid"). I hope you are not
seriously considering this idea :-) After all that's what the
platform_data was invented for.

Pawel

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