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From: Grant Likely <grant.likely@secretlab.ca>
To: Samuel Ortiz <sameo@linux.intel.com>
Cc: 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>,
	Greg Kroah-Hartman <gregkh@suse.de>
Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers
Date: Fri, 1 Apr 2011 17:58:44 -0600	[thread overview]
Message-ID: <BANLkTi=bq=OGzXFp7qiBr7x_BnGOWf=DRQ@mail.gmail.com> (raw)
In-Reply-To: <20110401235239.GE29397@sortiz-mobl>

On Fri, Apr 1, 2011 at 5:52 PM, Samuel Ortiz <sameo@linux.intel.com> wrote:
> On Fri, Apr 01, 2011 at 11:56:35AM -0600, Grant Likely wrote:
>> On Fri, Apr 1, 2011 at 11:47 AM, Andres Salomon <dilinger@queued.net> wrote:
>> > On Fri, 1 Apr 2011 13:20:31 +0200
>> > Samuel Ortiz <sameo@linux.intel.com> wrote:
>> >
>> >> Hi Grant,
>> >>
>> >> On Thu, Mar 31, 2011 at 05:05:22PM -0600, Grant Likely wrote:
>> > [...]
>> >> > Gah.  Not all devices instantiated via mfd will be an mfd device,
>> >> > which means that the driver may very well expect an *entirely
>> >> > different* platform_device pointer; which further means a very high
>> >> > potential of incorrectly dereferenced structures (as evidenced by a
>> >> > patch series that is not bisectable).  For instance, the xilinx ip
>> >> > cores are used by more than just mfd.
>> >> I agree. Since the vast majority of the MFD subdevices are MFD
>> >> specific IPs, I overlooked that part. The impacted drivers are the
>> >> timberdale and the DaVinci voice codec ones.
>>
>> Another option is you could do this for MFD devices:
>>
>> struct mfd_device {
>>         struct platform_devce pdev;
>>         struct mfd_cell *cell;
>> };
>>
>> However, that requires that drivers using the mfd_cell will *never*
>> get instantiated outside of the mfd infrastructure, and there is no
>> way to protect against this so it is probably a bad idea.
>>
>> Or, mfd_cell could be added to platform_device directly which would
>> *by far* be the safest option at the cost of every platform_device
>> having a mostly unused mfd_cell pointer.  Not a significant cost in my
>> opinion.
> I thought about this one, but I had the impression people would want to kill
> me for adding an MFD specific pointer to platform_device. I guess it's worth
> giving it a try since it would be a simple and safe solution.
> I'll look at it later this weekend.
>
> Thanks for the input.

[cc'ing gregkh because we're talking about modifying struct platform_device]

I'll back you up on this one.  It is a far better solution than the
alternatives.  At least with mfd, it covers a large set of devices.  I
think there is a strong argument for doing this.  Or alternatively,
the particular interesting fields from mfd_cell could be added to
platform_device.  What information do child devices need access to?

g.

  reply	other threads:[~2011-04-01 23:59 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 [this message]
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
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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