usbvision_trace
void usbvision_trace(bool b_force, char *fmt, ...);
#define TRACE_ALWAYS(x...) usbvision_trace(true, x);
#define TRACE(x...) usbvision_trace(false, x);
{ if(b_log_funcalls) usbvision_trace(false, x);}
{ if(b_log_funcret) usbvision_trace(false, x);}