Dynamic Reconfiguration

To support the minimal set of hot-plugging operations, drivers might need to implement support for bus quiesce, bus unquiesce, and reset. The scsi_hba_tran(9S) structure has been extended to support these new operations. If quiesce/unquiesce/reset is not required by hardware, no driver changes are needed.

The following new fields have been added to the scsi_hba_tran structure:

        int (*tran_quiesce)(dev_info_t *hba_dip);
        int (*tran_unquiesce)(dev_info_t *hba_dip);
        int (*tran_bus_reset)(dev_info_t *hba_dip, int level);

The new driver entry points are introduced in the following sections.

tran_quiesce(9E) and tran_unquiesce(9E)

Quiesce and unquiesce a SCSI bus.

        #include <sys/scsi/scsi.h>

        int prefixtran_quiesce(dev_info_t *hba_dip);

        int prefixtran_unquiesce(dev_info_t *hba_dip);

tran_quiesce(9E) and tran_unquiesce(9E) are required to be implemented by an HBA driver to support dynamic reconfiguration (DR) of SCSI devices on buses that were not designed to support hot-plugging.

The tran_quiesce() and tran_unquiesce() vectors in the scsi_hba_tran(9S) structure should be initialized during the HBA driver's attach(9E) to point to HBA entry points so they are called when a user initiates quiesce and unquiesce operations.

tran_quiesce(9E) is called by the SCSA framework to stop all activity on a SCSI bus prior to and during the reconfiguration of devices attached to the SCSI bus. tran_unquiesce(9E) is called by the SCSA framework to resume activity on the SCSI bus after the reconfiguration operation has been completed.

HBA drivers are required to handle tran_quiesce(9E) by waiting for all outstanding commands to complete before returning success. After the HBA has quiesced the bus, it must queue any new I/O requests from target drivers until the SCSA framework calls the corresponding tran_unquiesce(9E) entrypoint.

HBA drivers handle calls to tran_unquiesce(9E) by starting any target driver I/O requests that were queued by the HBA during the time the bus was quiesced.