Bent Bisballe Nyeng wrote: > In the time I have been using libusb there has always been a single > feature that I was missing: The ability to get a notification when a new > device is connected (or disconnected for that matter), and thereby > remove the need for continuous rescans of the usb bus. > > In a specific project that I once made a rescan actually interrupted an > active filetransfer on a MSD. Probably due to a bug in the MSD (some > custom thiny, not made by me) but it still points to the fact tha a bus > rescan is a quite "agrssive" thing to do in order to simply find out if > a device has been connected.
Well, I guess this depends on your level of abstraction. SOMEONE has to rescan the bus. In Windows, for example, you can subscribe to a "device changed" event from the PnP provider. However, that merely tells you that, somewhere in the system, some bus driver has reported a change in its set of child devices. The only way to find out WHICH devices came or went is to go rescan the bus you're interested in and compare the current list to your own list. Further, the notion of reattaching to a lost device is a tricky one. You're talking to a driver. That driver happens to be assigned to a particular hardware device. When that hardware device goes away, that driver instance is unloaded (or at least orphaned). When that hardware device comes back, it's seen as a brand-new device, and gets a brand-new driver set, with absolutely no connection to the orphaned driver you were talking to before. Certainly at the kernel level, there is simply no way to move those old driver connections to the new driver. Someone in user mode has to be using heuristics to make that connection. Some apps wouldn't want to be automatically reconnected. Thus, this ends up being an application-specific process. This is why hotplug has not already been added to libusb/libusbx. You have suggested a mechanism that would work for your application, but it's not at all clear that it is the right solution for every application. It's a very tricky problem. -- Tim Roberts, t...@probo.com Providenza & Boekelheide, Inc. ------------------------------------------------------------------------------ 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
