Writing Device Drivers


In general, a driver should not call USBA functions while the driver is holding a mutex. Therefore, race conditions in a client driver can be difficult to prevent.

Do not allow normal operational code to run simultaneously with the processing of asynchronous events such as a disconnect or CPR. These types of asynchronous events normally clean up and dismantle pipes and could disrupt the normal operational code.

One way to manage race conditions and protect normal operational code is to write a serialization facility that can acquire and release an exclusive-access synchronization object. You can write the serialization facility in such a way that the synchronization object is safe to hold through calls to USBA functions. The usbskel sample driver demonstrates this technique. See Sample USB Device Driver for information on the usbskel driver.