Re: Doubt on first access for PCIe device

[Jon Masters]

On 04/11/2017 10:15 AM, abhijit wrote:

> Here I am assuming, the completer ID will be device number and function 
> number that will eventually programmed in to  device. In that case, my 
> question is, without first write, how read request(VENDOR ID read) is 
> serviced/routed?

You'll want to read about PCIe enumeration at boot time and how the BIOS
walks the topology to assign these (which an OS may later re-number). In
particular, read about ECAM for configuration. This uses memory mapped
config space read/write accessors that target a memory address space
under the control of the root complex.

Jon.