Hi, I'm a developer of the leJOS open source project. We're currently looking for new ways for talking to USB devices. On Linux, we already use libusb with great success (however, port to libusb 1.0 and libusbx is pending). Some issues remain, like the one with libusb_detach_kernel_driver, which cannot be used reliably. (Explanation below)
Now on OS X, we need to talk to USB devices. A driver for these devices might already be installed. So that would probably need to be detached. Furthermore, the program that uses libusb is not running with elevated rights. it must be possible for a normal user to talk to these devices without having any special priviledges. Now on Linux, most of that is straight forward. In order to grant users access to certain devices, users are added to certain group and the matching udev rules are create. What would be the equivalent of that on OS X? Now detaching an already active driver is the next problem. On Linux, libusb_detach_kernel_driver is implement. Well, it suffers from a pretty annoying issue: libusb can detach libusb. Or as far as I understand: if libusb detaches a driver, it puts some kind of "general driver" in charge of the device. And if another process calls libusb_detach_kernel_driver, then this general driver is detached which kills the connection to the device for the process which is already talking to that device. And of course first getting the name of the attached driver, and then detaching it depending on the name gives birth to a race condition. When I mentioned that issue, it was thrown at me, that I should perform external synchronization. You know, like with serial devices, which you don't open unless you have locked a certain lock file. Now what's the default location of the lock files for USB devices? (Yes, I know that it doesn't exist. It's sarcasm.) Does a similar issue exist for OS X? I mean if detaching a driver is possible at all? Now device I'm talking about is the Lego NXT. Most of the time, it's some not very specific USB device that doesn't implement any special profile. But sometimes (in firmware update mode), it claims to be a cdc_acm device. I believe the driver by Lego handles the device in both modes. Regards, Sven ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_sfd2d_oct _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
