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SCSIPI(9)              NetBSD Kernel Developer's Manual              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); int scsipi_adapter_addref(struct scsipi_adapter *adapt); void scsipi_adapter_delref(struct scsipi_adapter *adapt);
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 com- mand (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 through the adapt_request() callback. The HBA driver signals completion (with or without errors) of the request through scsipi_done(). scsipi knows the resource's 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 int adapt_flags adapter properties SCSIPI_ADAPT_POLL_ONLY the HBA can't do interrupts SCSIPI_ADAPT_MPSAFE don't acquire the kernel lock when doing HBA call- backs 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, void *, 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() call- back) 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(9) 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 time- out int xs_control control flags (only flags of interest for HBA driv- ers 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 informa- tion. 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 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 follow- ing 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 queuing 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. scsipi_adapter_addref() and scsipi_adapter_delref() maintain a reference count, the enable callback is called appropriately for the first reference and the last reference. int adapt_getgeom(struct scsipi_periph *periph, struct disk_parms *params, u_long sectors) Optional callback, used by high-level drivers to get the ficti- tious geometry used by the controller's firmware for the speci- fied 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 call- back 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 con- trollers. 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 mem- bers: 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 immedi- ately. 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 IPL_BIO with the channel lock held. 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 pend- ing.
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 struc- ture 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. NetBSD 9.99 November 20, 2016 NetBSD 9.99
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