2013/3/22 Hans de Goede <hdego...@redhat.com>: > Hi, > > > On 03/22/2013 10:58 AM, Ludovic Rousseau wrote: >> >> 2013/3/22 Hans de Goede <hdego...@redhat.com>: >>> >>> Although automatic detaching may seem like a smart and user (programmer) >>> friendly thing to do, I'm very much against it! Let me explain >>> why: >>> >>> a) libusb_detach_kernel_driver on Linux will *always* work if the >>> user has the necessary rights on the usbfs device node >>> >>> b) When libusb_detach_kernel_driver is done, the driver sees a >>> device unplug, iow it is to the driver as if the user janked out >>> the device. >>> >>> Combine these 2 and now try to run some generic libusb using tool, >>> on a system with liberally set up usbfs permissions, then the following >>> could happen: >>> i) user is using a usb-stick, copies a large file to it >>> ii) user runs the libusb tool >>> iii) the tool detaches the usb-mass-storage driver before all cached >>> writes are flushed -> data and/or filesystem damage >>> >>> Not good. Now this can already happen, but making the driver detach >>> automatic (by default) makes it that much easier to happen, so strong >>> NACK to that idea. >> >> >> Another example: >> Your application uses libusb with automatic detach. >> You start the application and let it run. You forget about it but it >> is still running. >> Then you start the same application again. >> >> Instead of failing at the claim, the second execution will call detach >> and break the first execution of the application that was still >> running and using the device. > > > Actually that was a libusb bug and has been fixed > libusb_detach_kernel_driver, > now checks if the driver being detached is not usbfs itself, and if it > is returns LIBUSB_ERROR_BUSY. So this example will do the right thing > now (the app will get a LIBUSB_ERROR_BUSY both on its > libusb_detach_kernel_driver > and any subsequent libusb_claim_interface calls).
Great. >> So I propose to NOT add an automatic detach. Change: Auto detach is now fine for me. Bye -- Dr. Ludovic Rousseau ------------------------------------------------------------------------------ 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_d2d_mar _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
