On Sat, 18 Aug 2012, Alan Stern wrote: > > Looking at the output of usbmon, the kernel re-uses URB addresses. Is it > > possible that the urb is freed while the instruction is in > > *implement()*? > > In fact, the usbhid driver does not free any URBs until it is unbound > from the device. It keeps a circular queue of URBs and uses them in > sequence, over and over.
Correction: The usbhid driver keeps a circular queue of report structures and related data and uses _them_ in sequence, over and over. There is only one URB, which gets used for all the reports. More accurately, there is one URB for the interrupt-IN endpoint, one URB for the interrupt-OUT endpoint (if there is one), and one URB for endpoint 0. Each URB gets used for all the reports on its endpoint. One thing to look out for: Evidently usbhid_submit_report() does not check the HID_DISCONNECTED flag and will happily allow reports to be submitted after usbhid_stop() returns. This appears to be a bug. It could account for the behavior you're seeing. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
