SCSIPI(9)

NAME
scsipi - SCSI/ATAPI middle-layer interface

SYNOPSIS
#include <dev/scsipi/atapiconf.h>
#include <dev/scsipi/scsiconf.h>
void
scsipi_async_event(struct scsipi_channel *chan, scsipi_async_event_t event, void *arg);
void
scsipi_channel_freeze(struct scsipi_channel *chan, int count);
void
scsipi_channel_thaw(struct scsipi_channel *chan, int count);
void
scsipi_channel_timed_thaw(void *arg);
void
scsipi_periph_freeze(struct scsipi_periph *periph, int count);
void
scsipi_periph_thaw(struct scsipi_periph *periph, int count);
void
scsipi_periph_timed_thaw(void *arg);
void
scsipi_done(struct scsipi_xfer *xs);
void
scsipi_printaddr(struct scsipi_periph *periph);
int
scsipi_target_detach(struct scsipi_channel *chan, int target, int lun, int flags);
int
scsipi_thread_call_callback(struct scsipi_channel *chan, void (*callback)(struct scsipi_channel *, void *), void *arg);

DESCRIPTION
The scsipi system is the middle layer interface between SCSI/ATAPI host bus adapters (HBA) and high-level SCSI/ATAPI drivers. This document describes the interfaces provided by the scsipi layer towards the HBA layer. An HBA has to provide a pointer to a struct scsipi_adapter and one pointer per channel to a struct scsipi_channel. Once the SCSI or ATAPI bus is attached, the scsipi system will scan the bus and allocate a struct scsipi_periph for each device found on the bus. A high-level command (command sent from the high-level SCSI/ATAPI layer to the low-level HBA layer) is described by a struct scsipi_xfer.

A request is sent to the HBA driver though the adapt_request() callback. The HBA driver signals completion (with or without errors) of the request though scsipi_done(). scsipi knows the resources limits of the HBA (max number of concurrent requests per adapter of channel, and per periph), and will make sure the HBA won't receive more requests than it can handle.

The mid-layer can also handle QUEUE FULL and CHECK CONDITION events.

  INITIALISATION
An HBA driver has to allocate and initialize to 0 a struct scsipi_adapter and fill in the following members:
struct device *adapt_dev
    pointer to the HBA's struct device
int adapt_nchannels
    number of channels (or busses) of the adapter
int adapt_openings
    total number of commands the adapter can handle (may be replaced by chan_openings, see below)
int adapt_max_periph
    number of commands the adapter can handle per device

The following callbacks should be provided through the struct scsipi_adapter:
void (*adapt_request)(struct scsipi_channel *, scsipi_adapter_req_t, void *)
    mandatory
void (*adapt_minphys)(struct buf *)
    mandatory
int (*adapt_ioctl)(struct scsipi_channel *, u_long, caddr_t, int, struct lwp *)
    optional
int (*adapt_enable)(struct device *, int)
    optional, set to NULL if not used
int (*adapt_getgeom)(struct scsipi_periph *, struct disk_parms *, u_long)
    optional, set to NULL if not used
int (*adapt_accesschk)(struct scsipi_periph *, struct scsipi_inquiry_pattern *)
    optional, set to NULL if not used

The HBA driver has to allocate and initialize to 0 one struct scsipi_channel per channel and fill in the following members:
struct scsipi_adapter *chan_adapter
    Pointer to the HBA's struct scsipi_adapter
struct scsipi_bustype *chan_bustype
    should be initialized to either bus_atapi or bus_scsi, both defined in the scsipi code.
int chan_channel
    channel number (starting at 0)
int chan_flags
    channel flags:
    SCSIPI_CHAN_OPENINGS
        Use per-channel max number of commands chan_openings instead of per-adapter adapt_openings
    SCSIPI_CHAN_CANGROW
        This channel can grow its chan_openings or adapt_openings on request (via the adapt_request() callback)
    SCSIPI_CHAN_NOSETTLE
        Do not wait SCSI_DELAY seconds for devices to settle before probing (usually used by adapters that provide an abstracted view of the bus).
int chan_openings
    total number of commands the adapter can handle for this channel (used only if the SCSIPI_CHAN_OPENINGS flag is set)
chan_max_periph
    number of commands per device the adapter can handle on this channel (used only if the SCSIPI_CHAN_OPENINGS flag is set)
int chan_ntargets
    number of targets
int chan_nluns
    number of LUNs per target
int chan_id
    adapter's ID on this channel
int chan_defquirks
    default device quirks. Quirks are defined in dev/scsipi/scsipiconf.h and are usually set in the middle layer based on the device's inquiry data. For some kinds of adapters it may be convenient to have a set of quirks applied to all devices, regardless of the inquiry data.

The HBA driver attaches the SCSI or ATAPI bus (depending on the setting of chan_bustype) by passing a pointer to the struct scsipi_channel to the autoconf(4) machinery. The print function shall be either scsiprint() or atapiprint().

  OTHER DATA STRUCTURES
When scanning the bus, the scsipi system allocates a struct scsipi_periph for each device probed. The interesting fields are:
struct device *periph_dev
    pointer to the device's struct device
struct scsipi_channel *periph_channel
    pointer to the channel the device is connected to
int periph_quirks
    device quirks, defined in <dev/scsipi/scsipiconf.h>
int periph_target
    target ID, or drive number on ATAPI
int periph_lun
    LUN (currently not used on ATAPI)

A SCSI or ATAPI request is passed to the HBA through a struct scsipi_xfer. The HBA driver has access to the following data:
struct callout xs_callout
    callout for adapter use, usually for command timeout
int xs_control
    control flags (only flags of interest for HBA drivers are described):
    XS_CTL_POLL
        poll in the HBA driver for request completion (most likely because interrupts are disabled)
    XS_CTL_RESET
        reset the device
    XS_CTL_DATA_UIO
        xs_data points to a struct uio buffer
    XS_CTL_DATA_IN
        data is transferred from HBA to memory
    XS_CTL_DATA_OUT
        data is transferred from memory to HBA
    XS_CTL_DISCOVERY
        this xfer is part of a device discovery done by the middle layer
    XS_CTL_REQSENSE
        xfer is a request sense

int xs_status
    status flags:
    XS_STS_DONE
        xfer is done (set by scsipi_done())
    XS_STS_PRIVATE
        mask of flags reserved for HBA's use (0xf0000000)

struct scsipi_periph *xs_periph
    periph doing the xfer
int timeout
    command timeout, in milliseconds. The HBA should start the timeout at the time the command is accepted by the device. If the timeout happens, the HBA shall terminate the command through scsipi_done() with a XS_TIMEOUT error
struct scsipi_generic *cmd
    scsipi command to execute
int cmdlen
    len (in bytes) of the cmd buffer
u_char *data
    data buffer (this is either a DMA or uio address)
int datalen
    data length (in bytes, zero if uio)
int resid
    difference between datalen and how much data was really transferred
scsipi_xfer_result_t error
    error value returned by the HBA driver to mid-layer. See description of scsipi_done() for valid values
union {struct scsipi_sense_data scsi_sense; uint32_t atapi_sense;} sense
    where to store sense info if error is XS_SENSE or XS_SHORTSENSE
uint8_t status
    SCSI status; checked by middle layer when error is XS_BUSY (the middle layer handles SCSI_CHECK and SCSI_QUEUE_FULL)
uint8_t xs_tag_type
    SCSI tag type, set to 0 if untagged command
uint8_t xs_tag_id
    tag ID, used for tagged commands

  FUNCTIONS AND CALLBACKS
(*adapt_request)(struct scsipi_channel *chan, scsipi_adapter_req_t req, void *arg)
    Used by the mid-layer to transmit a request to the adapter. req can be one of:
    ADAPTER_REQ_RUN_XFER
        request the adapter to send a command to the device. arg is a pointer to the struct scsipi_xfer. Once the xfer is complete the HBA driver shall call scsipi_done() with updated status and error information.
    ADAPTER_REQ_GROW_RESOURCES
        ask the adapter to increase resources of the channel (grow adapt_openings or chan_openings) if possible. Support of this feature is optional. This request is called from the kernel completion thread. arg must be ignored.
    ADAPTER_REQ_SET_XFER_MODE
        set the xfer mode for a for I_T Nexus. This will be called once all LUNs of a target have been probed. arg points to a struct scsipi_xfer_mode defined as follows:
        int xm_target
            target for I_T Nexus
        int xm_mode
            bitmask of device capabilities
        int xm_period
            sync period
        int xm_offset
            sync offset

        xm_period and xm_offset shall be ignored for ADAPTER_REQ_SET_XFER_MODE. xm_mode holds the following bits:
        PERIPH_CAP_SYNC
            ST synchronous transfers
        PERIPH_CAP_WIDE16
            ST 16 bit wide transfers
        PERIPH_CAP_WIDE32
            ST 32 bit wide transfers
        PERIPH_CAP_DT
            DT transfers
        PERIPH_CAP_TQING
            tagged queueing
        Whenever the xfer mode changes, the driver should call scsipi_async_event() to notify the mid-layer.

    adapt_request() may be called from interrupt context.
adapt_minphys()
    pointer to the driver's minphys function. If the driver can handle transfers of size MAXPHYS, this can point to minphys().
adapt_ioctl()
    ioctl function for the channel. The only ioctl supported at this level is SCBUSIORESET for which the HBA driver shall issue a SCSI reset on the channel.
int adapt_enable(struct device *dev, int enable)
    Disable the adapter if enable is zero, or enable it if non-zero. Returns 0 if operation is successful, or error from sys/errno.h. This callback is optional, and is useful mostly for hot-plug devices. For example, this callback would power on or off the relevant PCMCIA socket for a PCMCIA controller.
int adapt_getgeom(struct scsipi_periph *periph, struct disk_parms *params, u_long sectors)
    Optional callback, used by high-level drivers to get the fictitious geometry used by the controller's firmware for the specified periph. Returns 0 if successful. See Adaptec drivers for details.
int adapt_accesschk(struct scsipi_periph *periph, struct scsipi_inquiry_pattern *inqbuf)
    Optional callback; if present the mid-layer uses it to check if it can attach a driver to the specified periph. If the callback returns a non-zero value, the periph is ignored by the scsipi code. This callback is used by adapters which want to drive some devices themselves, for example hardware RAID controllers.
scsipi_async_event(struct scsipi_channel *chan, scsipi_async_event_t event, void *arg)
    Asynchronous event notification for the mid-layer. event can be one of:
    ASYNC_EVENT_MAX_OPENINGS
        set max openings for a periph. Argument is a struct scsipi_max_openings with at least the following members:
        int mo_target
        int mo_lun
        int mo_openings

        Not all periphs may allow openings to increase; if not allowed the request is silently ignored.
    ASYNC_EVENT_XFER_MODE
        update the xfer mode for an I_T nexus. Argument is a struct scsipi_xfer_mode properly filled in. An ASYNC_EVENT_XFER_MODE call with PERIPH_CAP_TQING set in xm_mode is mandatory to activate tagged queuing.
    ASYNC_EVENT_RESET
        channel has been reset. No argument. HBA drivers have to issue ASYNC_EVENT_RESET events if they rely on the mid-layer for SCSI CHECK CONDITION handling.

scsipi_done(struct scsipi_xfer *xs)
    shall be called by the HBA when the xfer is complete, or when it needs to be requeued by the mid-layer. error in the scsipi_xfer shall be set to one of the following:
    XS_NOERROR
        xfer completed without error.
    XS_SENSE
        Check the returned SCSI sense for the error.
    XS_SHORTSENSE
        Check the ATAPI sense for the error.
    XS_DRIVER_STUFFUP
        Driver failed to perform operation.
    XS_RESOURCE_SHORTAGE
        Adapter resource shortage. The mid-layer will retry the command after some delay.
    XS_SELTIMEOUT
        The device timed out while trying to send the command
    XS_TIMEOUT
        The command was accepted by the device, but it didn't complete in allowed time.
    XS_BUSY
        The mid-layer will check status for additional details:
        SCSI_CHECK
            SCSI check condition. The mid-layer will freeze the periph queue and issue a REQUEST SENSE command. If the HBA supports tagged queuing, it shall remove and requeue any command not yet accepted by the HBA (or at last make sure no more commands will be sent to the device before the REQUEST SENSE is complete).
        SCSI_QUEUE_FULL
            The mid layer will adjust the periph's openings and requeue the command.
        SCSI_BUSY
            The mid-layer will requeue the xfer after delay.
    XS_RESET
        xfer destroyed by a reset; the mid-layer will requeue it.
    XS_REQUEUE
        Ask the mid-layer to requeue this command immediately.

    The adapter should not reference an xfer once scsipi_done(xfer) has been called, unless the xfer had XS_CTL_POLL set.

    scsipi_done() will call the adapt_request() callback again only if called with xs-error set to XS_NOERROR, and xfer doesn't have XS_CTL_POLL set. All other error conditions are handled by a kernel thread (once the HBA's interrupt handler has returned).
scsipi_printaddr(struct scsipi_periph *periph)
    print a kernel message with the periph's name, in the form device(controller:channel:target:lun).
scsipi_channel_freeze(struct scsipi_channel *chan, int count)
    Freeze the specified channel (requests are queued but not sent to HBA). The channel's freeze counter is increased by count.
scsipi_channel_thaw(struct scsipi_channel *chan, int count)
    Decrement the channel's freeze counter by count and process the queue if the counter goes to 0. In order to preserve command ordering, HBA drivers should not call scsipi_channel_thaw() before calling scsipi_done() for all commands in the HBA's queue which need to be requeued.
scsipi_periph_timed_thaw(void *arg)
    Call scsipi_channel_thaw(arg, 1). Intended to be used as callout(9) callback.
scsipi_periph_freeze(struct scsipi_periph *periph, int count)
scsipi_periph_thaw(struct scsipi_periph *periph)
scsipi_periph_timed_thaw(void *arg)
    Same as the channel counterparts, but only for one specific peripheral.
scsipi_target_detach(struct scsipi_channel *chan, int target, int lun, int flags)
    detach the periph associated with this I_T_L nexus. Both target and lun may be wildcarded using the magic value -1. flags is passed to config_detach() . Returns 0 if successful, or error code if a device couldn't be removed.
scsipi_thread_call_callback(struct scsipi_channel *chan, void (*callback)(struct scsipi_channel *, void *), void *arg)
    callback() will be called with chan and arg as arguments, from the channel completion thread. The callback is run at splbio. scsipi_thread_call_callback() will freeze the channel by one, it's up to the caller to thaw it when appropriate. Returns 0 if the callback was properly recorded, or EBUSY if the channel has already a callback pending.

FILES

sys/dev/scsiconf.h
    header file for use by SCSI HBA drivers

sys/dev/atapiconf.h
    header file for use by ATAPI HBA drivers

Both header files include sys/dev/scsipiconf.h which contains most structure definitions, function prototypes and macros.

EXAMPLES
The best examples are existing HBA drivers. Most of them sit in the sys/dev/ic directory.

HISTORY
The scsipi interface appeared in NetBSD 1.6.

AUTHORS
The scsipi interface was designed and implemented by Jason R. Thorpe. Manuel Bouyer converted most drivers to the new interface.