Hi, On 03/27/2013 05:22 PM, Ludovic Rousseau wrote: > 2013/3/25 Hans de Goede <hdego...@redhat.com>: >> Hi, >> >> >> On 03/23/2013 12:05 PM, Ludovic Rousseau wrote: >>> >>> 2013/3/23 Hans de Goede <hdego...@redhat.com>: >>>> >>>> We all seem to agree on that, which is good :) So it would be helpful >>>> to get some feedback on my proposed API for the opting in before I >>>> actually start coding this. Let me quote my own API proposal from >>>> another mail: >>>> >>>> Assuming all platforms will do auto-detach on interface claim (which >>>> makes sense given that drivers are usually per interface), we could >>>> make this a device_handle property, so then an app would do something >>>> like: >>>> >>>> libusb_device_handle *handle; >>>> >>>> libusb_open(dev, &handle); >>>> libusb_set_auto_detach(handle, 1); >>>> libusb_claim_interface(handle, x); >>>> >>>> With: >>>> void libusb_set_auto_detach(libusb_device_handle *dev, int auto_detach); >>> >>> >>> I propose to rename the function in libusb_set_auto_detach_kernel_driver() >> >> >> Ack. >> >> >>> >>> I also propose to give a symbolic name to the parameter value instead >>> of using 1. >>> Something like LIBUSB_AUTO_DETACH_KERNEL_DRIVER_ENABLE >>> >>> I don't know if we also need a LIBUSB_AUTO_DETACH_KERNEL_DRIVER_DISABLE >>> If not maybe the parameter can be removed. >>> Or maybe the function can be named: >>> libusb_set_parameter(handle, LIBUSB_AUTO_DETACH_KERNEL_DRIVER_ENABLE) >> >> >> I've been thinking about something more generic, ie: >> int libusb_set_parameter(libusb_device_handle *dev, int parameter, >> int value); >> >> But it seems better to me to just add per parameter set functions, these >> kind of multiplex functions are needlessly hard to use, and need demultiplex >> code in the implementation, which as ioctl code in the kernel shows, is >> easy at first but gets hard pretty quickly. >> >> Thinking more about this I propose to simply add a: >> >> void libusb_enable_auto_detach_kernel_driver(libusb_device_handle *dev); >> >> Function, this solves the whole needing defines for the argument problem, >> and the name makes it clear at once what the function does. > > The problem with a new function for each new parameter is that it is > hard to use in a program. If you want to support different (older) > versions of libusbx you will have to use something like: > > #ifdef HAVE_LIBUSB_ENABLE_AUTO_DETACH_KERNEL_DRIVER > libusb_enable_auto_detach_kernel_driver(device); > #else > libusb_enable_detach_kernel_driver(device); > #endif > > And add the corresponding test in configure.ac > > Maybe it is simpler to just always and only use > libusb_enable_detach_kernel_driver() > > For each new function added to libusbx the API and ABI version needs > to be increased. A program compiled with version N of the library > cannot be used with a previous version of the library (unless the > library is linked statically but that not the way to use on Linux).
Right, how I usually solve this in my usbredir code is simply bump the minimum version required in the pkg-config check in configure.ac, iow if people want to use the latest usbredir code, they need the latest libusb As for the ABI issue: 1) We should really start using symbol versioning on Linux for this 2) It is unusual to run with an older lib then an app was compiled against. > On the contrary, a generic function libusb_set_parameter() would > always be available and just return LIBUSB_ERROR_NOT_SUPPORTED for > unknown parameter. No more #ifdef dance and ABI issue. Well if the app sees the LIBUSB_ERROR_NOT_SUPPORTED for the auto-detach stuff and it knows it needs detach, it will need to fallback to doing detach the old way, so you're just replacing a #ifdef dance with a runtime dance... Which is exactly why I just bump the minimum version needed to build usually :) Regards, Hans ------------------------------------------------------------------------------ Own the Future-Intel® Level Up Game Demo Contest 2013 Rise to greatness in Intel's independent game demo contest. Compete for recognition, cash, and the chance to get your game on Steam. $5K grand prize plus 10 genre and skill prizes. Submit your demo by 6/6/13. http://p.sf.net/sfu/intel_levelupd2d _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
