On Fri, Apr 21, 2017 at 03:33:45PM +0530, abhijit naik wrote: > Hi Lorenzo, > Thank you very much for reply. > As you mentioned I noted that, "If a Function must generate a Completion > prior to the initial device Configuration Write Request, 0's must be > entered into the Bus Number and Device Number fields" > By above statement this means that completion ID will be 0x0000. For the > first device on any bus, device number will be 0 and function number will > be 0. > Isn't completer (for configuration read) packet will be addressing itself > instead of root complex with bus, device and function number 0? I don't understand what you are asking. The completion (containing the read data) is routed back to the initiator via ID (of the requester) routing. 2.2.4.2 2.2.9 Lorenzo > On Wed, Apr 19, 2017 at 3:56 PM, Lorenzo Pieralisi > <lorenzo.pieralisi@xxxxxxx> wrote: > > On Tue, Apr 11, 2017 at 07:45:40PM +0530, abhijit wrote: > > > > Hi All, > > > > I was referring Linux code for PCIe enumeration and I have one doubt > > w.r.t to very first operation that must be done on device. > > > > Currently while scanning for device, we directly read vendor ID from > > device. But PCIE base specification > > "CB-PCI_Express_Base_4.0r0.7_November-11-2016.pdf" section 2.2.6.2 > > specifies that, > > > > "Functions must capture the Bus and Device Numbers supplied with all > > Type 0 Configuration Write Requests completed by the Function and > > supply these numbers in the Bus and Device Number fields of the > > Requester ID for all Requests initiated by the Device/Function." > > Please note: > "for all Requests initiated by the Device/Function". > ^^^^^^^^^ > > 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? > > That's not initiated by the endpoint device, it is routed by > requester ID, which is the requester ID of the configuration > request - ie master (ie root complex) requester ID. > > Read 2.2.9 - Completion rules > > HTH, > Lorenzo > > -- > Best wishes, > Abhijit Naik
