accessing PCI configuration space

Discussion in 'Windows Vista Drivers' started by Maxim, Jun 17, 2008.

  1. Maxim

    Maxim Guest

    Is there a way to access PCI(E) config space from user mode in Windows 2003+?
    I.e., an equivalent of lspci command? Alternatively, does that information
    get cached
    somewhere (e.g. in the registry) by the OS?

    I know a driver can read that information out, but the idea is to get access
    to the
    information without having to load a driver for a device.

    The basic problem I am trying to solve is to determine the width of PCIE link
    in the slot that my device is plugged into. The only information I can find
    in the registry
    is vendor/product PCI IDs and a few other things, but nothing close to a
    full dump of
    PCI config space.
    Maxim, Jun 17, 2008
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  2. Maxim

    Maxim Guest

    Btw, I'll also take an answer in a form of an existing freeware application
    that does not install a driver :)
    Maxim, Jun 17, 2008
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  3. starting in vista (and subsequent OS's) the current link speed is exposed
    through a DEVPKEY (DEVPKEY_PciDevice_CurrentLinkSpeed in pciprop.h). before
    that, you need to figure this out for yourself...

    Doron Holan [MSFT], Jun 17, 2008
  4. Maxim

    Calvin Guan Guest

    You don't need a driver, it's free. does that count?
    Calvin Guan, Jun 18, 2008
  5. Maxim

    Maxim Guest

    bummer. oh well, thanks anyhow
    Maxim, Jun 18, 2008
  6. Maxim

    Maxim Guest

    i don't think it does, because it does not provide a dump of PCIE config
    space - only prints a few fields that are visible by other means (registry,
    device property details, devcon find pci\*, etc). same goes for !devext xxx
    Maxim, Jun 18, 2008
  7. Maxim

    DaveH Guest

    Maxim, I'm not sure what Doron has suggested is what you're after as the link
    speed (as defined by PCI Express spec) currently can only ever be 2.5Gb/s no
    matter what the width of the link is.

    If you really want to figure out the link width from user mode, you have to
    query the Link Status Register (offset 12h of PCI Express Capability
    Structure in PCI Config Space) which tells you the negotiated width of the
    link (1x, 2x, etc.). To access PCI Config Space you have to use PCI host
    bridge I/O ports namely CF8h and CFCh in a way described in PCI spec. In
    kernel mode, you can use the deprecated HalGetBusDataByOffset (recommended
    method is to create and send an IRP to PCI driver). In user mode, you could
    use _inpd, _outpd on above ports in a similar way to HalGetBusDataByOffset
    (check to know how).

    That said, I don't think this would be a good approach as accesses to above
    registers are not atomic and you might end up with some nasty side effects.

    DaveH, Jun 18, 2008
  8. Maxim

    luchnikov Guest

    This is Maxim, under a diff name... Do __inpb/__outpb really work in
    user mode? I'd imagine that Windows does not allow user-level access
    to hardware resources...
    luchnikov, Jun 20, 2008
  9. Maxim

    Don Burn Guest

    Using __inpb/__outpb is not allowed from user space in Windows. And to go
    further a great way to create subtle bugs is to access the PCI Config Space
    registers I know a firm being sued for doing this.

    Don Burn (MVP, Windows DDK)
    Windows 2k/XP/2k3 Filesystem and Driver Consulting
    Remove StopSpam to reply
    Don Burn, Jun 20, 2008
  10. Maxim

    luchnikov Guest

    By merely reading the space? I imagine they are writing it...

    Anyway, looks like w/o a filter driver I am SOL. See my other post -
    I tried getting PCI config data in STORPORT miniport driver via
    StorPortGetBusData, without much luck.

    Too bad there isn't some IOCTL you can send to the PCI bus driver to
    get this data in Win2K3
    luchnikov, Jun 20, 2008
  11. Maxim

    Don Burn Guest

    To read a specific location in PCI config space you have to write the
    address to one register, then read from the other register. Since you have
    no access to the lock doing this, you can get subtle bugs of the form:

    System writes address reg
    User writes address reg
    Systems reads "data"
    User reads "data"

    Of course the system is not reading what it expects!

    Don Burn (MVP, Windows DDK)
    Windows 2k/XP/2k3 Filesystem and Driver Consulting
    Remove StopSpam to reply
    Don Burn, Jun 20, 2008
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