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From: Ben Hutchings <bhutchings@solarflare.com>
To: Samuel Ortiz <sameo@linux.intel.com>
Cc: Greg KH <gregkh@suse.de>,
	Grant Likely <grant.likely@secretlab.ca>,
	Andres Salomon <dilinger@queued.net>,
	linux-kernel@vger.kernel.org,
	Mark Brown <broonie@opensource.wolfsonmicro.com>,
	khali@linux-fr.org, ben-linux@fluff.org,
	Peter Korsgaard <jacmet@sunsite.dk>,
	Mauro Carvalho Chehab <mchehab@infradead.org>,
	David Brownell <dbrownell@users.sourceforge.net>,
	linux-i2c@vger.kernel.org, linux-media@vger.kernel.org,
	netdev@vger.kernel.org, spi-devel-general@lists.sourceforge.net,
	Mocean Laboratories <info@mocean-labs.com>
Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers
Date: Wed, 06 Apr 2011 18:16:49 +0100	[thread overview]
Message-ID: <1302110209.2840.20.camel@bwh-desktop> (raw)
In-Reply-To: <20110406170537.GB2757@sortiz-mobl>

On Wed, 2011-04-06 at 19:05 +0200, Samuel Ortiz wrote:
> Hi Greg,
> 
> On Wed, Apr 06, 2011 at 08:58:05AM -0700, Greg KH wrote:
> > On Wed, Apr 06, 2011 at 05:23:23PM +0200, Samuel Ortiz wrote:
> > > --- a/include/linux/device.h
> > > +++ b/include/linux/device.h
> > > @@ -33,6 +33,7 @@ struct class;
> > >  struct subsys_private;
> > >  struct bus_type;
> > >  struct device_node;
> > > +struct mfd_cell;
> > >  
> > >  struct bus_attribute {
> > >  	struct attribute	attr;
> > > @@ -444,6 +445,8 @@ struct device {
> > >  	struct device_node	*of_node; /* associated device tree node */
> > >  	const struct of_device_id *of_match; /* matching of_device_id from driver */
> > >  
> > > +	struct mfd_cell	*mfd_cell; /* MFD cell pointer */
> > > +
> > 
> > What is a "MFD cell pointer" and why is it needed in struct device?
> An MFD cell is an MFD instantiated device.
> MFD (Multi Function Device) drivers instantiate platform devices. Those
> devices drivers sometimes need a platform data pointer, sometimes an MFD
> specific pointer, and sometimes both. Also, some of those drivers have been
> implemented as MFD sub drivers, while others know nothing about MFD and just
> expect a plain platform_data pointer.
> 
> We've been faced with the problem of being able to pass both MFD related data
> and a platform_data pointer to some of those drivers. Squeezing the MFD bits
> in the sub driver platform_data pointer doesn't work for drivers that know
> nothing about MFDs. It also adds an additional dependency on the MFD API to
> all MFD sub drivers. That prevents any of those drivers to eventually be used
> as plain platform device drivers.
> So, adding an MFD cell pointer to the device structure allows us to cleanly
> pass both pieces of information, while keeping all the MFD sub drivers
> independant from the MFD core if they want/can.

Why isn't an MFD the parent of its component devices?

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.


  reply	other threads:[~2011-04-06 17:16 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-03  3:54 [RFC] [PATCH 0/19] mfd sharing support Andres Salomon
2011-02-03  3:55 ` [PATCH 01/19] mfd-core: unconditionally add mfd_cell to every platform_device Andres Salomon
2011-02-03  3:58 ` [PATCH 02/19] jz4740: mfd_cell is now implicitly available to drivers Andres Salomon
2011-02-03  8:09   ` Jean Delvare
2011-02-03  4:01 ` [PATCH 03/19] ab3550: " Andres Salomon
2011-02-04  8:20   ` Mattias Wallin
2011-02-03  4:03 ` [PATCH 04/19] ab3100: " Andres Salomon
2011-02-03 12:52   ` Linus Walleij
2011-02-03  4:04 ` [PATCH 05/19] asic3: " Andres Salomon
2011-02-03  4:05 ` [PATCH 06/19] htc-pasic3: " Andres Salomon
2011-02-03  4:08 ` [PATCH 07/19] timberdale: " Andres Salomon
2011-03-31 23:05   ` Grant Likely
2011-04-01 11:20     ` Samuel Ortiz
2011-04-01 17:47       ` Andres Salomon
2011-04-01 17:56         ` Grant Likely
2011-04-01 18:00           ` Grant Likely
2011-04-01 23:52           ` Samuel Ortiz
2011-04-01 23:58             ` Grant Likely
2011-04-02  0:10               ` Andres Salomon
2011-04-04 10:03               ` Samuel Ortiz
2011-04-05  3:04                 ` Grant Likely
2011-04-06 15:23                   ` Samuel Ortiz
2011-04-06 15:58                     ` Greg KH
2011-04-06 17:05                       ` Samuel Ortiz
2011-04-06 17:16                         ` Ben Hutchings [this message]
2011-04-06 17:51                           ` Samuel Ortiz
2011-04-06 18:07                             ` Ben Hutchings
2011-04-06 17:56                         ` Greg KH
2011-04-06 18:25                           ` Andres Salomon
2011-04-06 18:38                             ` Greg KH
2011-04-07  8:04                               ` Grant Likely
2011-04-06 18:47                           ` Samuel Ortiz
2011-04-06 18:59                             ` Felipe Balbi
2011-04-06 22:09                               ` Greg KH
2011-04-07  8:09                                 ` Felipe Balbi
2011-04-07 13:40                               ` Samuel Ortiz
2011-04-07 14:35                                 ` Grant Likely
2011-04-07 15:03                                   ` Samuel Ortiz
2011-04-07 18:06                                     ` Grant Likely
2011-04-07 16:24                   ` Grant Likely
2011-04-01 18:26         ` Samuel Ortiz
2011-02-03  4:09 ` [PATCH 08/19] t7166xb: " Andres Salomon
2011-02-03  4:11 ` [PATCH 09/19] wl1273: " Andres Salomon
2011-02-03  4:12 ` [PATCH 10/19] sh_mobile_sdhi: " Andres Salomon
2011-02-03  4:13 ` [PATCH 11/19] tc6393xb: " Andres Salomon
2011-02-03  4:15 ` [PATCH 12/19] twl4030: " Andres Salomon
2011-02-03  6:05   ` Dmitry Torokhov
2011-02-03  6:39     ` Andres Salomon
2011-02-03  6:53       ` Dmitry Torokhov
2011-02-03  7:03         ` Andres Salomon
2011-02-03  9:31           ` Mark Brown
2011-02-05  2:39             ` Andres Salomon
2011-02-05  3:25               ` Andres Salomon
2011-02-03 12:23           ` Peter Ujfalusi
2011-02-04 10:41           ` Uwe Kleine-König
2011-02-03  4:16 ` [PATCH 13/19] tc6387xb: " Andres Salomon
2011-02-03  4:17 ` [PATCH 14/19] janz: " Andres Salomon
2011-02-03  4:20 ` [PATCH 15/19] mc13xxx: " Andres Salomon
2011-02-04  9:34   ` Uwe Kleine-König
2011-02-04 10:13     ` Uwe Kleine-König
2011-02-04 10:16     ` Andres Salomon
2011-02-03  4:21 ` [PATCH 16/19] mfd-core: drop platform_data/data_size from core mfd_cell struct Andres Salomon
2011-02-03  4:22 ` [PATCH 17/19] mfd-core: add refcounting support to mfd_cells Andres Salomon
2011-02-03  4:23 ` [PATCH 18/19] mfd-core: add platform_device sharing support for mfd Andres Salomon
2011-02-03  4:26 ` [PATCH 19/19] cs5535-mfd: add sharing for acpi/pms cells Andres Salomon

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