On 10/31/2013 04:40 PM, [email protected] wrote: > Hi! > On 10/31/2013 05:38 AM, Wanlong Gao wrote: >> On 10/30/2013 07:21 PM, Alexey Kodanev wrote: >>> There is another way to check that PCI Express config space of pci devices >>> can be read successfully. >>> Firstly, find out if a device has a PCI Express Capability: we should get >>> a correct config address offset from the dev's structure (dev->pcie_cap). >>> Using the offset, read a PCI Express header. Check if we can get the right >>> PCI Express CAP ID from the header (it must match the PCI_CAP_ID_EXP macro). >> This can PASS here, thank you. >> >> Why did the original method always FAIL? > > The original code has wrong offset, should be reg = 0x100 at least (as it > written in comment): >> int reg = 100, len = 4; /*PCI-Exp enhanced config register 0x100, 4 implies >> dword access */ > > I don't know about that magic number 0x14011 in the original code. Comments > said that we can find a constant value from that offset, but in truth, we can > find any of the PCI_EXT_CAP_ID_* macors in the first 16 bits or none if > device doesn't have Extended Configuration Space. It can be AER (ERR in the > macro) and it could be any other ID (it depends on the device). > > better find a particular offset using the kernel function, for example: > pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR); /* it will find > Advanced Error Reporting structure */ > > Then get the header (first 4 bytes). First 16 bits should be AER_ID, that it > is to say 0x0001. From bit 16 to bit 19 - capability version (can be 1h or > 2h). The other bits contain the offset to the next PCI Express Capability > structure or zero if it is the last one. That kind of header will never equal > to 0x14011, that's is why the original method will always fail even with the > right offset. >
OK, got it, thank you for your explaination. Wanlong Gao > ------------------------------------------------------------------------------ Android is increasing in popularity, but the open development platform that developers love is also attractive to malware creators. Download this white paper to learn more about secure code signing practices that can help keep Android apps secure. http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk _______________________________________________ Ltp-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ltp-list
