On Sun, Aug 4, 2013 at 9:08 AM, Pete Batard <p...@akeo.ie> wrote: > On 2013.08.04 00:51, Alan Stern wrote: >> Out of curiosity, what data do you need to request from the parent hub? > > Now that I've looked a bit through old e-mails, it seems that these are > config descriptors, coming from a Windows > IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION request. I'll have to > re-check what goes on the bus though, as we also have an > IOCTL_USB_GET_NODE_CONNECTION_INFORMATION elsewhere (which provides us > data such as the device connection speed).
IOCTL_USB_GET_NODE_CONNECTION_INFORMATION reference: http://libusb.6.n5.nabble.com/libusb-windows-devices-only-detected-in-late-pass-ignoring-tp4463538p4490768.html http://msdn.microsoft.com/en-us/library/windows/hardware/ff537319(v=vs.85).aspx This is one call that Travis and I were quite against before. On the other hand, later it seems to me that this call to the hub may be inavoidable in the context of current libusbx. It is not used in libusb-win32 and libusbK. > So I may be misremembering things, as the data we seem to derive from > the first IOCTL isn't used for the topology, but to cache the actual > config descriptor (which libusb mandates us to cache) and it looks like > it's really a matter of caching our descriptors on Windows after all. Ref: http://msdn.microsoft.com/en-us/library/windows/hardware/ff537310(v=vs.85).aspx >> And why does requesting that data send a query to the child device for >> its device descriptor? > > I guess that Microsoft decided that their IOCTL for the config desc > should always translate as a bus request. And there is no API call I > know of that would allow us to get cached data for those during enum. -- Xiaofan ------------------------------------------------------------------------------ Get your SQL database under version control now! Version control is standard for application code, but databases havent caught up. So what steps can you take to put your SQL databases under version control? Why should you start doing it? Read more to find out. http://pubads.g.doubleclick.net/gampad/clk?id=49501711&iu=/4140/ostg.clktrk _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
