Messages in this thread |  | | | From | Kumar Gala <> | | Subject | Re: what's a platform device? | | Date | Thu, 23 Feb 2006 10:13:45 -0600 |
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On Feb 23, 2006, at 3:33 AM, Russell King wrote:
> On Wed, Feb 22, 2006 at 03:47:40PM -0600, Kumar Gala wrote: >> 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. > > We have at least one example where we have a single PCI function > containing more than one type of functionality which are the parallel > port and serial cards [*]. Normally, the different types of > functionality are accessible via different BARs which at least gives > some logical separation. > > It's not really a good model because you have to have a special PCI > probe driver to register the various functionalities with the > subsystems > rather than using the generic 8250_pci and parport_pci drivers > directly. > Also it can have problems if you want to have (eg) serial built-in and > i2c as a module. > > The alternative as Greg points out is to implement a pseudo > bus_type, but > I start to worry about the overhead associated with doing so. > > Given the choice between a small PCI "probe" driver for a small number > of functionalities and a complete driver model infrastructure, I'd > prefer the former over the latter.
I might not have been clear before. The number of functions that are implemented in the FPGA is not a small hand full. I think Greg's idea of creating a bus is appropriate for the scale.
- kumar
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