linux-kernel - Re: [PATCH 15/19] mc13xxx: mfd_cell is now implicitly available to drivers

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Message-ID: <20110204101338.GI30452@pengutronix.de>
Date:	Fri, 4 Feb 2011 11:13:38 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Andres Salomon <dilinger@...ued.net>
Cc:	Russell King <linux@....linux.org.uk>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, Richard Purdie <rpurdie@...ys.net>,
	Sascha Hauer <kernel@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org,
	Liam Girdwood <lrg@...mlogic.co.uk>
Subject: Re: [PATCH 15/19] mc13xxx: mfd_cell is now implicitly available to
 drivers

Hello,

On Fri, Feb 04, 2011 at 10:34:58AM +0100, Uwe Kleine-König wrote:
> And I think this patch has a conceptual problem, too.  In my opionion
> platform_data is the point to hand over platform specific data to a
> driver.  driver_data is something that is private to the driver and has
> to be considered opaque for the platform.  The driver was sort of OK
> before ...

So consequently I propose the patch below.  I'm sure that a few drivers
will break, but IMHO that's OK.

And by the way, did you know that platform_set_drvdata can fail and you
have no nice way to notice that but to do:

	dev_set_drvdata(dev, mypreciousdata);
	if (dev_get_drvdata(dev) != mypreciousdata)
		goto fail;

Best regards
Uwe

------>8-----------
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Date: Fri, 4 Feb 2011 11:00:42 +0100
Subject: [PATCH] MFD: platform_set_drvdata should be only called by drivers

driver data is data private to drivers so it's not a point to hand over
data to the driver by the platform.  That's what platform_data is available
for.  The only place platform_set_drvdata should be called is in a
driver that has bound the device in question.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
 drivers/mfd/mfd-core.c   |    1 -
 include/linux/mfd/core.h |    3 ---
 2 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index d83ad0f..8d06e0c 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -37,7 +37,6 @@ static int mfd_add_device(struct device *parent, int id,
 		goto fail_device;
 
 	pdev->dev.parent = parent;
-	platform_set_drvdata(pdev, cell->driver_data);
 
 	if (cell->data_size) {
 		ret = platform_device_add_data(pdev,
diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
index 835996e..88bb7b5 100644
--- a/include/linux/mfd/core.h
+++ b/include/linux/mfd/core.h
@@ -30,9 +30,6 @@ struct mfd_cell {
 	int			(*suspend)(struct platform_device *dev);
 	int			(*resume)(struct platform_device *dev);
 
-	/* driver-specific data for MFD-aware "cell" drivers */
-	void			*driver_data;
-
 	/* platform_data can be used to either pass data to "generic"
 	   driver or as a hook to mfd_cell for the "cell" drivers */
 	void			*platform_data;
-- 
1.7.2.3

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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