On Wed, Jul 8, 2009 at 10:53 PM, Xiaofan Chen<xiaof...@gmail.com> wrote: > On Wed, Jul 8, 2009 at 12:43 PM, Xiaofan Chen<xiaof...@gmail.com> wrote: >> I will ask in the libusb mailing list why it still works under Linux >> and Mac OS X. > > Here is the answer from Alan Stern in the libusb mailing list. > >>> Apparently the code is not correct. >>> After this one, the usb_handle should not be valid any more. >>> usb_reset(result->usb_handle); >>> >>> So it will fail the next two. >>> /* usb_set_configuration required under win32 >>> */ >>> usb_set_configuration(result->usb_handle, >>> dev->config[0].bConfigurationValue); >>> usb_claim_interface(result->usb_handle, 0); >>> >>> But in reality, the above "wrong codes" seem to work under Linux >>> and Mac OS X even though it failed under Windows. >>> >>> Why does it work under Linux and Mac OS X? >>> Does the usb_handle survive the usb_reset() under Linux and Mac OS X? >> >> Under Linux, sometimes it does and sometimes it doesn't. It depends on >> whether any of the descriptors have changed and on what version of the >> kernel you are using; with 2.6.27 or later the handle won't survive. >> >>> Is this something related to the following? >>> http://kerneltrap.org/mailarchive/linux-usb/2008/11/28/4259024 >> >> No; it is related to this: >> >> http://marc.info/?l=linux-usb&m=121425133223338&w=2 >> >> Alan Stern >> >> > > So the code is apparently wrong. It will not work in the later version > of the Linux kernel. So we need to find a better patch even under Linux. >
This is also in line with the libusb 0.1 documentation. http://libusb.sourceforge.net/doc/function.usbreset.html **************** Name usb_reset -- Resets a device Description int usb_reset(usb_dev_handle *dev); usb_reset resets the specified device by sending a RESET down the port it is connected to. Returns 0 on success or < 0 on error. Causes re-enumeration: After calling usb_reset, the device will need to re-enumerate and thusly, requires you to find the new device and open a new handle. The handle used to call usb_reset will no longer work. ****************** -- Xiaofan http://mcuee.blogspot.com _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
