Writing Device Drivers

Fault Management Data and Status Structure

Driver error handling callbacks are passed a pointer to a data structure that contains common fault management data and status for error handling.

The data structure ddi_fm_error contains an FMA protocol ENA for the current error, the status of the error handler callback, an error expectation flag, and any potential access or DMA handles associated with an error detected by the parent nexus.


This field is initialized by the calling parent nexus and might have been incremented along the error handling propagation chain before reaching the driver's registered callback routine. If the driver detects a related error of its own, it should increment this ENA prior to calling ddi_fm_ereport_post().

fme_acc_handle, fme_dma_handle

These fields contain a valid access or DMA handle if the parent was able to associate an error detected at its level to a handle mapped or bound by the device driver.


The fme_flag is set to DDI_FM_ERR_EXPECTED if the calling parent determines the error was the result of a DDI_CAUTIOUS_ACC protected operation. In this case, the fme_acc_handle is valid and the driver should check for and report only errors not associated with the DDI_CAUTIOUS_ACC protected operation. Otherwise, fme_flag is set to DDI_FM_ERR_UNEXPECTED and the driver must perform the full range of error handling tasks.


Upon return from its error handler callback, the driver must set fme_status to one of the following values:

  • DDI_FM_OK – No errors were detected and the operational state of this device instance remains the same.

  • DDI_FM_FATAL – An error has occurred and the driver considers it to be fatal to the system. For example, a call to pci_ereport_post(9F) might have detected a system fatal error. In this case, the driver should report any additional error information it might have in the context of the driver.

  • DDI_FM_NONFATAL – An error has been detected by the driver but is not considered fatal to the system. The driver has identified the error and has either isolated the error or is committing that it will isolate the error.

  • DDI_FM_UNKNOWN – An error has been detected, but the driver is unable to isolate the device or determine the impact of the error on the operational state of the system.