Hello Francois, > I ended up modifying avarice to use libusb-1.0 directly. > It is a hack more than a nice clean architecture improvment ... but it > could be useful if somebody sees the same issue.
Well, actually I'd be very interested in getting a clean implementation of libusb-1.0. The entire reason for the "USB daemon" subprocess, and all the multiprocessing around it is that the libusb-0.1 API did not allow to select() (or poll()) for anything from USB. However, AVaRICE is in the need of polling two channels for IO multiplexing, the GDB channel, and the ICE channel. The GDB channel is just a socket, so it's easy to poll for it. Historically (for the first JTAGICE, as well as the JTAGICEmkII connected through a standard serial port), the ICE connection was a simple serial one, which was also easy to poll. Both connections were handled in a single select() system call. However, when implementing USB access to the JTAGICEmkII using the libusb-0.1 API, there were no provisions to get access to a standard filedescriptor which could be polled. Thus, I invented the "USB daemon", as a subprocess being forked off the main process. The entire purpose of this child process was to operate the libusb API, eventually sleep for USB messages, and connect to its parent through a couple of pipe descriptors. As a pipe descriptor is a standard Unix filedescriptor which can be used in select(), this any messages arriving on the USB could be made the parent process wakeup, and continue its processing. As the libusb-1.0 API has provisions to obtain the Unix filedescriptor being used by the library, it ought to be possible to return to the single-process single-thread scenario we have been at years ago. As this eliminates a number of potential pitfalls (see the multiprocessing problems reported for Solaris), and in general makes the code more straightforward again, I'd appreciate a solution towards that direction. I do hope a change like this would not cause too much compatibility issues for all the platforms supported, notably Cygwin. However, the libusb-1.0 API is now several years old, and for sure did replace the old 0.1 de-facto standard API. -- cheers, J"org .-.-. --... ...-- -.. . DL8DTL http://www.sax.de/~joerg/ NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-) ------------------------------------------------------------------------------ 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_nov _______________________________________________ avarice-user mailing list avarice-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/avarice-user
