Messages in this thread | | | From | Kumar Gala <> | Subject | Re: what's a platform device? | Date | Thu, 23 Feb 2006 01:04:22 -0600 |
| |
>> 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. > > Yes, as they have no "bus" to attach too. That's why they are there, > they are for devices with no bus, but are merely "raw" memory mapped > devices.
I'm not sure I follow this. How is PCI different? How would "kumar" bus be different?
>> 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 :) > > I guess I look at your FPGA as a PCI "bridge" chip, that bridges > between > the PCI bus, and your "kumar" bus (for lack of a better name). Your > devices hang off of that bus, which is attached to the FPGA, which is > attached to the pci bridge, and so on. If you use the platform > bus, you > break that link. > > Does that make sense?
This makes sense, but you seem to be talking about hierarchy more the functionality. I agree in your description of hierarchy.
I was looking at it from a functional point of view, maybe more from the device view then from the bus. I need a struct device type that contains resources, a name, an id. I'll do matching based on name. From a functional point of view platform does all this.
Based on your description would you say that a platform_device's parent device should always be platform_bus? [I'm getting at the fact that we allow pdev->dev.parent to be set by the caller of platform_device_add].
Hmm, as I think about this further, I think that its more coincidence that the functionality for the "kumar" bus is equivalent to that of the "platform" bus.
> Russell probably has other thoughts about this.
Hopefully he'll provide his thoughts :)
- kumar
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |