On 2012.09.03 21:16, Chris McClelland wrote: > Firstly thanks for the lively fork! It's great that libusb is being so > actively developed.
Thanks. It's always nice to hear from more users making the switch. > I'm in the process of debugging some host-side code and Cypress FX2LP > firmware. If you're dealing with the FX2LP, then I'll start with an aside: Do you know that we plan to introduce our own version of fxload, as a libusbx sample? This work is currently happening in one of my personal branches [1], but, bugfixes permitting, I'm hoping it will be included with full FX2/FX2LP support for libusbx v1.0.13, that is to be released soon. FX3 support should follow shortly after. > Things work fine on Linux and on MacOSX, but things go awry on > Windows (using WinUSB driver). I coult show you traces of things > actually going wrong on Windows, but I notice even when things go well, > the Linux message-flow differs from the Windows message-flow; I'd like > to understand there reason for these differences. If you're dealing with set configuration, and trying to set a configuration that is different than the default one, then things are expected not to work on Windows when using WinUSB [2]. Currently we're not sending SET_CONFIGURATION on the bus unless it's for the default one, and if you run your app with libusbx logging set to at least warning (which you are strongly encouraged to do during development - see libusb_set_debug [3]), you should have seen a warning about it [4]. > On Linux, running my libusb-1.0 test program three times gives this: > > http://pastebin.com/raw.php?i=0jGbaAxM > > Notice that the message sequence is: > > 1) Write 0x00 bytes to EP0: SET_CONFIGURATION(0x0001, 0x0000) > 2) Read 0x10 bytes from EP0: 0x80(0x0000, 0x0000) > 3) Write 0x05 bytes to EP2: 0x00, 0x00, 0x00, 0x00, 0x01 > 4) Write 0x01 byte to EP2: 0x10 > > And notice that this sequence is repeated three times (for three > separate invocations of the test program). > > Now the same code built against libusbx-1.0.12 on Windows, running on > the same host inside a VirtualBox VM: > > http://pastebin.com/raw.php?i=9dPb0uiC > > Notice that the message sequence is now: > > 1a) Read 0x09 bytes from EP0: GET_DESCRIPTOR(0x0200, 0x0000) > 1b) Read 0x2E bytes from EP0: GET_DESCRIPTOR(0x0200, 0x0000) > 2) Read 0x10 bytes from EP0: 0x80(0x0000, 0x0000) > 3) Write 0x05 bytes to EP2: 0x00, 0x00, 0x00, 0x00, 0x01 > 4) Write 0x01 byte to EP2: 0x10 > > Notice that, again, the message sequence is repeated three times (for > three separate invocations of the test program). Also notice that 2, 3 & > 4 are exactly the same as they were on Linux, but the call to > SET_CONFIGURATION on Linux has been replaced with a pair of calls to > GET_DESCRIPTOR on Windows. Most likely that's because we can't set the configuration you request using WinUSB, so we don't bother sending that message to the device. This is a WinUSB limitation. On the other hand, to conform with the Linux centric libusb enumeration model, we have to issue a few get_descriptor requests to external hubs get some of the data we need, and as the OS does not cache it, those queries will appear on the bus. We've had a lengthy debate about what we could do to avoid sending these descriptor requests every time we re-enumerate on Windows, but for the time being, you should expect to see those. > If I run the same code natively on a dedicated Windows machine (and use > USBTrace to sniff), neither the SET_CONFIGURATION nor the GET_DESCRIPTOR > are sent; it just goes straight into 2, 3 & 4. That's strange. I'd expect to see some querying of descriptors for any external hub on Windows. As to SET_CONFIGURATION, unless you're trying for the default conf, it will not be sent on the bus. Finally, note that 1.0.13 will also introduce support for the libusb0 and libusbK Windows drivers, that are less limited as WinUSB, so we will hopefully be able to switch configurations in the future when using those. Most likely, this will happen in 1.0.14 rather than 1.0.13 though. Regards, /Pete [1] https://github.com/pbatard/libusbx/commits/0K [2] https://github.com/libusbx/libusbx/wiki/Windows-Backend#wiki-Known_Restrictions [3] http://libusbx.sourceforge.net/api-1.0/group__lib.html#ga5f8376b7a863a5a8d5b8824feb8a427a [4] https://github.com/libusbx/libusbx/blob/master/libusb/os/windows_usb.c#L2890 ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
