Date: Wed, 22 Feb 2006 15:47:40 -0600 (CST)
From: Kumar Gala <galak@kernel.crashing.org>
To: Russell King <rmk+lkml@arm.linux.org.uk>, Greg KH <greg@kroah.com>
cc: linux-kernel@vger.kernel.org
Subject: what's a platform device?
Message-ID: <Pine.LNX.4.44.0602221517370.21264-100000@gate.crashing.org>
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Guys,

I was hoping to get your opinion on a question I had.  The question comes 
down to what we think a "platform device" is.

The situation I have is an FPGA connected over PCI.  The FPGA implements
various device functionality (serial ports, I2C controller, IR, etc.) as a
single PCI device/function.  The FPGA breaks any notion of a true PCI
device, it uses PCI as a device interconnect more than anything else.

In talking to Greg about this, he suggested I just create a new bus_type
for this similar to what is being done for usb-serial.  As I started to
think about what I wanted ended up being a platform_device plus a sysfs
entry for the MMIO region.

So, it seems that a "platform device" is a pretty generic concept now.  Do 
you guys thing its acceptable to use a platform device for my needs or 
should I create some new bus_type?  Do we have a better definition of what 
a platform device is or might be?

If we're ok with my use of platform device for this, I assume no one has
an issue with adding a sysfs attribute to platform devices to expose the
MMIO regions similar to what we do for PCI today.

thanks

- kumar

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