libdc1394
2.2.2
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#include <dc1394/juju/firewire-cdev.h>
struct fw_cdev_get_cycle_timer - read cycle timer register : system time, in microseconds since the Epoch : Cycle Time register contents
The FW_CDEV_IOC_GET_CYCLE_TIMER ioctl reads the isochronous cycle timer and also the system clock (CLOCK_REALTIME). This allows to express the receive time of an isochronous packet as a system time.
consists of 7 bits cycleSeconds, 13 bits cycleCount, and 12 bits cycleOffset, in host byte order. Cf. the Cycle Time register per IEEE 1394 or Isochronous Cycle Timer register per OHCI-1394.
In version 1 and 2 of the ABI, this ioctl returned unreliable (non- monotonic) values on certain controllers.