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Writing Device Drivers
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SCSA HBA Interfaces

SCSA HBA interfaces include HBA entry points, HBA data structures, and an HBA framework.

SCSA HBA Entry Point Summary

SCSA defines a number of HBA driver entry points. These entry points are listed in the following table. The entry points are called by the system when a target driver instance connected to the HBA driver is configured. The entry points are also called when the target driver makes a SCSA request. See Entry Points for SCSA HBA Drivers for more information.

Table 18-1 SCSA HBA Entry Point Summary

Function Name

Called as a Result of

tran_abort(9E)

Target driver calling scsi_abort(9F)

tran_bus_reset(9E)

System resetting bus

tran_destroy_pkt(9E)

Target driver calling scsi_destroy_pkt(9F)

tran_dmafree(9E)

Target driver calling scsi_dmafree(9F)

tran_getcap(9E)

Target driver calling scsi_ifgetcap(9F)

tran_init_pkt(9E)

Target driver calling scsi_init_pkt(9F)

tran_quiesce(9E)

System quiescing bus

tran_reset(9E)

Target driver calling scsi_reset(9F)

tran_reset_notify(9E)

Target driver calling scsi_reset_notify(9F)

tran_setcap(9E)

Target driver calling scsi_ifsetcap(9F)

tran_start(9E)

Target driver calling scsi_transport(9F)

tran_sync_pkt(9E)

Target driver calling scsi_sync_pkt(9F)

tran_tgt_free(9E)

System detaching target device instance

tran_tgt_init(9E)

System attaching target device instance

tran_tgt_probe(9E)

Target driver calling scsi_probe(9F)

tran_unquiesce(9E)

System resuming activity on bus

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.

Per-Target Instance Data

An HBA driver must allocate a scsi_hba_tran(9S) structure during attach(9E). The HBA driver must then initialize the vectors in this transport structure to point to the required entry points for the HBA driver. This scsi_hba_tran structure is then passed into scsi_hba_attach_setup(9F).

The scsi_hba_tran structure contains a tran_hba_private field, which can be used to refer to the HBA driver's per-instance state.

Each scsi_address(9S) structure contains a pointer to the scsi_hba_tran structure. In addition, the scsi_address structure provides the target, that is, a_target, and logical unit (a_lun) addresses for the particular target device. Each entry point for the HBA driver is passed a pointer to the scsi_address structure, either directly or indirectly through the scsi_device(9S) structure. As a result, the HBA driver can reference its own state. The HBA driver can also identify the target device that is addressed.

The following figure illustrates the HBA data structures for transport operations.

Figure 18-3 HBA Transport Structures
Diagram shows the relationships of structures involved in the HBA transport layer.

Transport Structure Cloning

Cloning can be useful if an HBA driver needs to maintain per-target private data in the scsi_hba_tran(9S) structure. Cloning can also be used to maintain a more complex address than is provided in the scsi_address(9S) structure.

In the cloning process, the HBA driver must still allocate a scsi_hba_tran structure at attach(9E) time. The HBA driver must also initialize the tran_hba_private soft state pointer and the entry point vectors for the HBA driver. The difference occurs when the framework begins to connect an instance of a target driver to the HBA driver. Before calling the HBA driver's tran_tgt_init(9E) entry point, the framework clones the scsi_hba_tran structure that is associated with that instance of the HBA. Accordingly, each scsi_address structure that is allocated and initialized for a particular target device instance points to a per-target instance copy of the scsi_hba_tran structure. The scsi_address structures do not point to the scsi_hba_tran structure that is allocated by the HBA driver at attach() time.

An HBA driver can use two important pointers when cloning is specified. These pointers are contained in the scsi_hba_tran structure. The first pointer is the tran_tgt_private field, which the driver can use to point to per-target HBA private data. The tran_tgt_private pointer is useful, for example, if an HBA driver needs to maintain a more complex address than a_target and a_lun provide. The second pointer is the tran_sd field, which is a pointer to the scsi_device(9S) structure referring to the particular target device.

When specifying cloning, the HBA driver must allocate and initialize the per-target data. The HBA driver must then initialize the tran_tgt_private field to point to this data during its tran_tgt_init(9E) entry point. The HBA driver must free this per-target data during its tran_tgt_free(9E) entry point.

When cloning, the framework initializes the tran_sd field to point to the scsi_device structure before the HBA driver tran_tgt_init() entry point is called. The driver requests cloning by passing the SCSI_HBA_TRAN_CLONE flag to scsi_hba_attach_setup(9F). The following figure illustrates the HBA data structures for cloning transport operations.

Figure 18-4 Cloning Transport Operation
Diagram shows an example of cloned HBA structures.

SCSA HBA Functions

SCSA also provides a number of functions. The functions are listed in the following table, for use by HBA drivers.

Table 18-2 SCSA HBA Functions

Function Name

Called by Driver Entry Point

scsi_hba_init(9F)

_init(9E)

scsi_hba_fini(9F)

_fini(9E)

scsi_hba_attach_setup(9F)

attach(9E)

scsi_hba_detach(9F)

detach(9E)

scsi_hba_tran_alloc(9F)

attach(9E)

scsi_hba_tran_free(9F)

detach(9E)

scsi_hba_probe(9F)

tran_tgt_probe(9E)

scsi_hba_pkt_alloc(9F)

tran_init_pkt(9E)

scsi_hba_pkt_free(9F)

tran_destroy_pkt(9E)

scsi_hba_lookup_capstr(9F)

tran_getcap(9E) and tran_setcap(9E)

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  Published under the terms fo the Public Documentation License Version 1.01. Design by Interspire