Message-ID: <4D5AF554.2030208@codeaurora.org>
Date: Tue, 15 Feb 2011 13:51:16 -0800
From: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
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To: dilinger@queued.net, Samuel Ortiz <sameo@linux.intel.com>
CC: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Mark Brown <broonie@opensource.wolfsonmicro.com>,
        Ian Lartey <ian@opensource.wolfsonmicro.com>,
        Dimitris Papastamos <dp@opensource.wolfsonmicro.com>,
        Linus Walleij <linus.walleij@stericsson.com>,
        Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>,
        Michael Hennerich <michael.hennerich@analog.com>,
        linux-arm-msm@vger.kernel.org
Subject: platform data and mfd design question
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Currently all the mfd devices declare their struct mfd_cell 
sub_devices[] array within the core driver. The platform data to them is 
either passed in as a part of the core driver's platform data.

Msm on the other hand declares the struct mfd_cell subdevice[] array in 
the board file and passes this on to the core driver via platfom data.
This code can be found here (sorry for the long url - it is convinient 
to click on it),
https://www.codeaurora.org/gitweb/quic/la/?p=kernel/msm.git;a=blob;f=arch/arm/mach-msm/board-msm8x60.c;h=ed9e9a7674b5ee443f25af828a0044ff99fac483;hb=refs/heads/android-msm-2.6.35
look for static struct mfd_cell pm8058_subdevs[]

This gives one the convenience of changing the mfd_cells and their 
platform data in the board file itself. There are boards where the 
platform data of some cells changes and in some cases we dont even add a 
particular cell.

This design makes the core driver very light weight. All it does is 
calls mfd_add_devices on the cell array passed from its platform data.

Will this be acceptable in mainline OR do we need to change to follow 
how others in drivers/mfd do it which is to define the mfd_cell array in 
the core file itself and manipulate their platform data before doing 
mfd_add_devices.


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