On Feb 22, 2006, at 10:39 PM, Greg KH wrote:
On Wed, Feb 22, 2006 at 03:47:40PM -0600, Kumar Gala wrote:
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?
Well, your FPGA is a pci device, right? It's only the devices that
hang
off of it that you are concerned about. I really think you should
make
your own bus type, as it's not much work, and it would not disturb the
existing platform devices, which do not know about mmio regions like
PCI.
Yes, the FPGA is a pci device.
Not sure I follow exactly what you mean by the fact that platform
devices dont know about mmio regions. They know about struct
resource and iomem_resource & ioport_resource.
I think I might be missing something fundamental here. In
implementing my own bus_type, I'll end up introducing my own struct
foobar_device which looked pretty much like struct platform_device.
Then I'll need a set of functions to assign resources, etc.
I got no issue implementing my own bus_type, but I clearly feel like
I'm missing something here (just not sure what it is :)
- kumar
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