Writing Device Drivers

SCSA HBA Data Structures

SCSA defines data structures to enable the exchange of information between the target and HBA drivers. The following data structures are included:

`scsi_hba_tran()` Structure

Each instance of an HBA driver must allocate a scsi_hba_tran(9S) structure by using the scsi_hba_tran_alloc(9F) function in the attach(9E) entry point. The scsi_hba_tran_alloc() function initializes the scsi_hba_tran structure. The HBA driver must initialize specific vectors in the transport structure to point to entry points within the HBA driver. After the scsi_hba_tran structure is initialized, the HBA driver exports the transport structure to SCSA by calling the scsi_hba_attach_setup(9F) function.

Caution –

Because SCSA keeps a pointer to the transport structure in the driver-private field on the devinfo node, HBA drivers must not use ddi_set_driver_private(9F). HBA drivers can, however, use ddi_get_driver_private(9F) to retrieve the pointer to the transport structure.

The SCSA interfaces require the HBA driver to supply a number of entry points that are callable through the scsi_hba_tran structure. See Entry Points for SCSA HBA Drivers for more information.

The scsi_hba_tran structure contains the following fields:

struct scsi_hba_tran {
    dev_info_t          *tran_hba_dip;          /* HBAs dev_info pointer */
    void                *tran_hba_private;      /* HBA softstate */
    void                *tran_tgt_private;      /* HBA target private pointer */
    struct scsi_device  *tran_sd;               /* scsi_device */
    int                 (*tran_tgt_init)();     /* Transport target */
                                                /* Initialization */
    int                 (*tran_tgt_probe)();    /* Transport target probe */
    void                (*tran_tgt_free)();     /* Transport target free */
    int                 (*tran_start)();        /* Transport start */
    int                 (*tran_reset)();        /* Transport reset */
    int                 (*tran_abort)();        /* Transport abort */
    int                 (*tran_getcap)();       /* Capability retrieval */
    int                 (*tran_setcap)();       /* Capability establishment */
    struct scsi_pkt     *(*tran_init_pkt)();    /* Packet and DMA allocation */
    void                (*tran_destroy_pkt)();  /* Packet and DMA */
                                                /* Deallocation */
    void                (*tran_dmafree)();      /* DMA deallocation */
    void                (*tran_sync_pkt)();     /* Sync DMA */
    void                (*tran_reset_notify)(); /* Bus reset notification */
    int                 (*tran_bus_reset)();    /* Reset bus only */
    int                 (*tran_quiesce)();      /* Quiesce a bus */
    int                 (*tran_unquiesce)();    /* Unquiesce a bus */
    int                 tran_interconnect_type; /* transport interconnect */
};

The following descriptions give more information about these scsi_hba_tran structure fields:

tran_hba_dip: Pointer to the HBA device instance dev_info structure. The function scsi_hba_attach_setup(9F) sets this field.
tran_hba_private: Pointer to private data maintained by the HBA driver. Usually, tran_hba_private contains a pointer to the state structure of the HBA driver.
tran_tgt_private: Pointer to private data maintained by the HBA driver when using cloning. By specifying SCSI_HBA_TRAN_CLONE when calling scsi_hba_attach_setup(9F), the scsi_hba_tran(9S) structure is cloned once per target. This approach enables the HBA to initialize this field to point to a per-target instance data structure in the tran_tgt_init(9E) entry point. If SCSI_HBA_TRAN_CLONE is not specified, tran_tgt_private is NULL, and tran_tgt_private must not be referenced. See Transport Structure Cloning for more information.
tran_sd: Pointer to a per-target instance scsi_device(9S) structure used when cloning. If SCSI_HBA_TRAN_CLONE is passed to scsi_hba_attach_setup(9F), tran_sd is initialized to point to the per-target scsi_device structure. This initialization takes place before any HBA functions are called on behalf of that target. If SCSI_HBA_TRAN_CLONE is not specified, tran_sd is NULL, and tran_sd must not be referenced. See Transport Structure Cloning for more information.
tran_tgt_init: Pointer to the HBA driver entry point that is called when initializing a target device instance. If no per-target initialization is required, the HBA can leave tran_tgt_init set to NULL.
tran_tgt_probe: Pointer to the HBA driver entry point that is called when a target driver instance calls scsi_probe(9F). This routine is called to probe for the existence of a target device. If no target probing customization is required for this HBA, the HBA should set tran_tgt_probe to scsi_hba_probe(9F).
tran_tgt_free: Pointer to the HBA driver entry point that is called when a target device instance is destroyed. If no per-target deallocation is necessary, the HBA can leave tran_tgt_free set to NULL.
tran_start: Pointer to the HBA driver entry point that is called when a target driver calls scsi_transport(9F).
tran_reset: Pointer to the HBA driver entry point that is called when a target driver calls scsi_reset(9F).
tran_abort: Pointer to the HBA driver entry point that is called when a target driver calls scsi_abort(9F).
tran_getcap: Pointer to the HBA driver entry point that is called when a target driver calls scsi_ifgetcap(9F).
tran_setcap: Pointer to the HBA driver entry point that is called when a target driver calls scsi_ifsetcap(9F).
tran_init_pkt: Pointer to the HBA driver entry point that is called when a target driver calls scsi_init_pkt(9F).
tran_destroy_pkt: Pointer to the HBA driver entry point that is called when a target driver calls scsi_destroy_pkt(9F).
tran_dmafree: Pointer to the HBA driver entry point that is called when a target driver calls scsi_dmafree(9F).
tran_sync_pkt: Pointer to the HBA driver entry point that is called when a target driver calls scsi_sync_pkt(9F).
tran_reset_notify: Pointer to the HBA driver entry point that is called when a target driver calls tran_reset_notify(9E).
tran_bus_reset: The function entry that resets the SCSI bus without resetting targets.
tran_quiesce: The function entry that waits for all outstanding commands to complete and blocks (or queues) any I/O requests issued.
tran_unquiesce: The function entry that allows I/O activities to resume on the SCSI bus.
tran_interconnect_type: Integer value denoting interconnect type of the transport as defined in the services.h header file.

`scsi_address` Structure

The scsi_address(9S) structure provides transport and addressing information for each SCSI command that is allocated and transported by a target driver instance.

The scsi_address structure contains the following fields:

struct scsi_address {
    struct scsi_hba_tran    *a_hba_tran;    /* Transport vectors */
    ushort_t                a_target;       /* Target identifier */
    uchar_t                 a_lun;          /* LUN on that target */
    uchar_t                 a_sublun;       /* Sub LUN on that LUN */
                                            /* Not used */
};

a_hba_tran: Pointer to the scsi_hba_tran(9S) structure, as allocated and initialized by the HBA driver. If SCSI_HBA_TRAN_CLONE was specified as the flag to scsi_hba_attach_setup(9F), a_hba_tran points to a copy of that structure.
a_target: Identifies the SCSI target on the SCSI bus.
a_lun: Identifies the SCSI logical unit on the SCSI target.

`scsi_device` Structure

The HBA framework allocates and initializes a scsi_device(9S) structure for each instance of a target device. The allocation and initialization occur before the framework calls the HBA driver's tran_tgt_init(9E) entry point. This structure stores information about each SCSI logical unit, including pointers to information areas that contain both generic and device-specific information. One scsi_device(9S) structure exists for each target device instance that is attached to the system.

If the per-target initialization is successful, the HBA framework sets the target driver's per-instance private data to point to the scsi_device(9S) structure, using ddi_set_driver_private(9F). Note that an initialization is successful if tran_tgt_init() returns success or if the vector is null.

The scsi_device(9S) structure contains the following fields:

struct scsi_device {
    struct scsi_address           sd_address;    /* routing information */
    dev_info_t                    *sd_dev;       /* device dev_info node */
    kmutex_t                      sd_mutex;      /* mutex used by device */
    void                          *sd_reserved;
    struct scsi_inquiry           *sd_inq;
    struct scsi_extended_sense    *sd_sense;
    caddr_t                       sd_private;    /* for driver's use */
};

where:

sd_address: Data structure that is passed to the routines for SCSI resource allocation.
sd_dev: Pointer to the target's dev_info structure.
sd_mutex: Mutex for use by the target driver. This mutex is initialized by the HBA framework. The mutex can be used by the target driver as a per-device mutex. This mutex should not be held across a call to scsi_transport(9F) or scsi_poll(9F). See Chapter 3, Multithreading for more information on mutexes.
sd_inq: Pointer for the target device's SCSI inquiry data. The scsi_probe(9F) routine allocates a buffer, fills the buffer in, and attaches the buffer to this field.
sd_sense: Pointer to a buffer to contain request sense data from the device. The target driver must allocate and manage this buffer itself. See the target driver's attach(9E) routine in attach() Entry Point for more information.
sd_private: Pointer field for use by the target driver. This field is commonly used to store a pointer to a private target driver state structure.

`scsi_pkt` Structure (HBA)

To execute SCSI commands, a target driver must first allocate a scsi_pkt(9S) structure for the command. The target driver must then specify its own private data area length, the command status, and the command length. The HBA driver is responsible for implementing the packet allocation in the tran_init_pkt(9E) entry point. The HBA driver is also responsible for freeing the packet in its tran_destroy_pkt(9E) entry point. See scsi_pkt Structure (Target Drivers) for more information.

The scsi_pkt(9S) structure contains these fields:

struct scsi_pkt {
    opaque_t pkt_ha_private;             /* private data for host adapter */
    struct scsi_address pkt_address;     /* destination address */
    opaque_t pkt_private;                /* private data for target driver */
    void (*pkt_comp)(struct scsi_pkt *); /* completion routine */
    uint_t  pkt_flags;                   /* flags */
    int     pkt_time;                    /* time allotted to complete command */
    uchar_t *pkt_scbp;                   /* pointer to status block */
    uchar_t *pkt_cdbp;                   /* pointer to command block */
    ssize_t pkt_resid;                   /* data bytes not transferred */
    uint_t  pkt_state;                   /* state of command */
    uint_t  pkt_statistics;              /* statistics */
    uchar_t pkt_reason;                  /* reason completion called */
};

where:

pkt_ha_private: Pointer to per-command HBA-driver private data.
pkt_address: Pointer to the scsi_address(9S) structure providing address information for this command.
pkt_private: Pointer to per-packet target-driver private data.
pkt_comp: Pointer to the target-driver completion routine called by the HBA driver when the transport layer has completed this command.
pkt_flags: Flags for the command.
pkt_time: Specifies the completion timeout in seconds for the command.
pkt_scbp: Pointer to the status completion block for the command.
pkt_cdbp: Pointer to the command descriptor block (CDB) for the command.
pkt_resid: Count of the data bytes that were not transferred when the command completed. This field can also be used to specify the amount of data for which resources have not been allocated. The HBA must modify this field during transport.
pkt_state: State of the command. The HBA must modify this field during transport.
pkt_statistics: Provides a history of the events that the command experienced while in the transport layer. The HBA must modify this field during transport.
pkt_reason: Reason for command completion. The HBA must modify this field during transport.

SCSA HBA Data Structures

scsi_hba_tran() Structure

scsi_address Structure

scsi_device Structure

scsi_pkt Structure (HBA)

`scsi_hba_tran()` Structure

`scsi_address` Structure

`scsi_device` Structure

`scsi_pkt` Structure (HBA)