SCSI lower level drivers. Lower level drivers (LLDs) are variously called
host bus adapter (HBA) drivers and host drivers (HD). A "host" in this
context is a bridge between a computer IO bus (e.g. PCI or ISA) and a
-single SCSI initiator device on a SCSI transport. An "initiator" device
-(SCSI terminology) sends SCSI commands to "target" SCSI devices (e.g.
-disks). There can be many LLDs in a running system, but only one per
-hardware type. Most LLDs can control one or more SCSI HBAs. Some HBAs
-contain multiple hosts.
+single SCSI initiator port on a SCSI transport. An "initiator" port
+(SCSI terminology, see SAM-3 at http://www.t10.org) sends SCSI commands
+to "target" SCSI ports (e.g. disks). There can be many LLDs in a running
+system, but only one per hardware type. Most LLDs can control one or more
+SCSI HBAs. Some HBAs contain multiple hosts.
In some cases the SCSI transport is an external bus that already has
its own subsystem in Linux (e.g. USB and ieee1394). In such cases the
LLD mid level LLD
===-------------------=========--------------------===------
scsi_host_alloc() -->
-scsi_add_host() --------+
+scsi_add_host() ---->
+scsi_scan_host() -------+
|
slave_alloc()
slave_configure() --> scsi_adjust_queue_depth()
The hotplug concept may be extended to SCSI devices. Currently, when an
-HBA is added, the scsi_add_host() function causes a scan for SCSI devices
+HBA is added, the scsi_scan_host() function causes a scan for SCSI devices
attached to the HBA's SCSI transport. On newer SCSI transports the HBA
may become aware of a new SCSI device _after_ the scan has completed.
An LLD can use this sequence to make the mid level aware of a SCSI device:
struct tags. Both can be still found in the SCSI subsystem, but
the typedefs have been moved to a single file, scsi_typedefs.h to
make their future removal easier, for example:
-"typedef struct scsi_host_template Scsi_Host_Template;"
+"typedef struct scsi_cmnd Scsi_Cmnd;"
Also, most C99 enhancements are encouraged to the extent they are supported
by the relevant gcc compilers. So C99 style structure and array
Mid level supplied functions
============================
These functions are supplied by the SCSI mid level for use by LLDs.
-The names (i.e. entry points) of these functions are exported (mainly in
-scsi_syms.c) so an LLD that is a module can access them. The kernel will
+The names (i.e. entry points) of these functions are exported
+so an LLD that is a module can access them. The kernel will
arrange for the SCSI mid level to be loaded and initialized before any LLD
is initialized. The functions below are listed alphabetically and their
names all start with "scsi_".
Summary:
+ scsi_activate_tcq - turn on tag command queueing
scsi_add_device - creates new scsi device (lu) instance
- scsi_add_host - perform sysfs registration and SCSI bus scan.
- scsi_add_timer - (re-)start timer on a SCSI command.
+ scsi_add_host - perform sysfs registration and set up transport class
scsi_adjust_queue_depth - change the queue depth on a SCSI device
- scsi_assign_lock - replace default host_lock with given lock
scsi_bios_ptable - return copy of block device's partition table
scsi_block_requests - prevent further commands being queued to given host
- scsi_delete_timer - cancel timer on a SCSI command.
+ scsi_deactivate_tcq - turn off tag command queueing
scsi_host_alloc - return a new scsi_host instance whose refcount==1
scsi_host_get - increments Scsi_Host instance's refcount
scsi_host_put - decrements Scsi_Host instance's refcount (free if 0)
scsi_remove_device - detach and remove a SCSI device
scsi_remove_host - detach and remove all SCSI devices owned by host
scsi_report_bus_reset - report scsi _bus_ reset observed
- scsi_set_device - place device reference in host structure
- scsi_to_pci_dma_dir - convert SCSI subsystem direction flag to PCI
- scsi_to_sbus_dma_dir - convert SCSI subsystem direction flag to SBUS
+ scsi_scan_host - scan SCSI bus
scsi_track_queue_full - track successive QUEUE_FULL events
scsi_unblock_requests - allow further commands to be queued to given host
scsi_unregister - [calls scsi_host_put()]
Details:
+/**
+ * scsi_activate_tcq - turn on tag command queueing ("ordered" task attribute)
+ * @sdev: device to turn on TCQ for
+ * @depth: queue depth
+ *
+ * Returns nothing
+ *
+ * Might block: no
+ *
+ * Notes: Eventually, it is hoped depth would be the maximum depth
+ * the device could cope with and the real queue depth
+ * would be adjustable from 0 to depth.
+ *
+ * Defined (inline) in: include/scsi/scsi_tcq.h
+ **/
+void scsi_activate_tcq(struct scsi_device *sdev, int depth)
+
+
/**
* scsi_add_device - creates new scsi device (lu) instance
* @shost: pointer to scsi host instance
* Might block: yes
*
* Notes: This call is usually performed internally during a scsi
- * bus scan when an HBA is added (i.e. scsi_add_host()). So it
+ * bus scan when an HBA is added (i.e. scsi_scan_host()). So it
* should only be called if the HBA becomes aware of a new scsi
- * device (lu) after scsi_add_host() has completed. If successful
- * this call we lead to slave_alloc() and slave_configure() callbacks
+ * device (lu) after scsi_scan_host() has completed. If successful
+ * this call can lead to slave_alloc() and slave_configure() callbacks
* into the LLD.
*
* Defined in: drivers/scsi/scsi_scan.c
/**
- * scsi_add_host - perform sysfs registration and SCSI bus scan.
+ * scsi_add_host - perform sysfs registration and set up transport class
* @shost: pointer to scsi host instance
* @dev: pointer to struct device of type scsi class
*
* Might block: no
*
* Notes: Only required in "hotplug initialization model" after a
- * successful call to scsi_host_alloc().
+ * successful call to scsi_host_alloc(). This function does not
+ * scan the bus; this can be done by calling scsi_scan_host() or
+ * in some other transport-specific way. The LLD must set up
+ * the transport template before calling this function and may only
+ * access the transport class data after this function has been called.
*
* Defined in: drivers/scsi/hosts.c
**/
/**
- * scsi_add_timer - (re-)start timer on a SCSI command.
- * @scmd: pointer to scsi command instance
- * @timeout: duration of timeout in "jiffies"
- * @complete: pointer to function to call if timeout expires
- *
- * Returns nothing
- *
- * Might block: no
- *
- * Notes: Each scsi command has its own timer, and as it is added
- * to the queue, we set up the timer. When the command completes,
- * we cancel the timer. An LLD can use this function to change
- * the existing timeout value.
- *
- * Defined in: drivers/scsi/scsi_error.c
- **/
-void scsi_add_timer(struct scsi_cmnd *scmd, int timeout,
- void (*complete)(struct scsi_cmnd *))
-
-
-/**
- * scsi_adjust_queue_depth - change the queue depth on a SCSI device
+ * scsi_adjust_queue_depth - allow LLD to change queue depth on a SCSI device
* @sdev: pointer to SCSI device to change queue depth on
* @tagged: 0 - no tagged queuing
- * MSG_SIMPLE_TAG - simple (unordered) tagged queuing
+ * MSG_SIMPLE_TAG - simple tagged queuing
* MSG_ORDERED_TAG - ordered tagged queuing
* @tags Number of tags allowed if tagged queuing enabled,
* or number of commands the LLD can queue up
* LLD. [Specifically during and after slave_configure() and prior to
* slave_destroy().] Can safely be invoked from interrupt code. Actual
* queue depth change may be delayed until the next command is being
- * processed.
+ * processed. See also scsi_activate_tcq() and scsi_deactivate_tcq().
*
* Defined in: drivers/scsi/scsi.c [see source code for more notes]
*
int tags)
-/**
- * scsi_assign_lock - replace default host_lock with given lock
- * @shost: a pointer to a scsi host instance
- * @lock: pointer to lock to replace host_lock for this host
- *
- * Returns nothing
- *
- * Might block: no
- *
- * Defined in: include/scsi/scsi_host.h .
- **/
-void scsi_assign_lock(struct Scsi_Host *shost, spinlock_t *lock)
-
-
/**
* scsi_bios_ptable - return copy of block device's partition table
* @dev: pointer to block device
/**
- * scsi_delete_timer - cancel timer on a SCSI command.
- * @scmd: pointer to scsi command instance
- *
- * Returns 1 if able to cancel timer else 0 (i.e. too late or already
- * cancelled).
+ * scsi_deactivate_tcq - turn off tag command queueing
+ * @sdev: device to turn off TCQ for
+ * @depth: queue depth (stored in sdev)
*
- * Might block: no [may in the future if it invokes del_timer_sync()]
+ * Returns nothing
*
- * Notes: All commands issued by upper levels already have a timeout
- * associated with them. An LLD can use this function to cancel the
- * timer.
+ * Might block: no
*
- * Defined in: drivers/scsi/scsi_error.c
+ * Defined (inline) in: include/scsi/scsi_tcq.h
**/
-int scsi_delete_timer(struct scsi_cmnd *scmd)
+void scsi_deactivate_tcq(struct scsi_device *sdev, int depth)
/**
* area for the LLD's exclusive use.
* Both associated refcounting objects have their refcount set to 1.
* Full registration (in sysfs) and a bus scan are performed later when
- * scsi_add_host() is called.
+ * scsi_add_host() and scsi_scan_host() are called.
*
* Defined in: drivers/scsi/hosts.c .
**/
/**
- * scsi_set_device - place device reference in host structure
+ * scsi_scan_host - scan SCSI bus
* @shost: a pointer to a scsi host instance
- * @pdev: pointer to device instance to assign
- *
- * Returns nothing
*
- * Might block: no
- *
- * Defined in: include/scsi/scsi_host.h .
- **/
-void scsi_set_device(struct Scsi_Host * shost, struct device * dev)
-
-
-/**
- * scsi_to_pci_dma_dir - convert SCSI subsystem direction flag to PCI
- * @scsi_data_direction: SCSI subsystem direction flag
- *
- * Returns DMA_TO_DEVICE given SCSI_DATA_WRITE,
- * DMA_FROM_DEVICE given SCSI_DATA_READ
- * DMA_BIDIRECTIONAL given SCSI_DATA_UNKNOWN
- * else returns DMA_NONE
- *
- * Might block: no
+ * Might block: yes
*
- * Notes: The SCSI subsystem now uses the same values for these
- * constants as the PCI subsystem so this function is a nop.
- * The recommendation is not to use this conversion function anymore
- * (in the 2.6 kernel series) as it is not needed.
- *
- * Defined in: drivers/scsi/scsi.h .
- **/
-int scsi_to_pci_dma_dir(unsigned char scsi_data_direction)
-
-
-/**
- * scsi_to_sbus_dma_dir - convert SCSI subsystem direction flag to SBUS
- * @scsi_data_direction: SCSI subsystem direction flag
- *
- * Returns DMA_TO_DEVICE given SCSI_DATA_WRITE,
- * FROM_DEVICE given SCSI_DATA_READ
- * DMA_BIDIRECTIONAL given SCSI_DATA_UNKNOWN
- * else returns DMA_NONE
- *
- * Notes: The SCSI subsystem now uses the same values for these
- * constants as the SBUS subsystem so this function is a nop.
- * The recommendation is not to use this conversion function anymore
- * (in the 2.6 kernel series) as it is not needed.
- *
- * Might block: no
+ * Notes: Should be called after scsi_add_host()
*
- * Defined in: drivers/scsi/scsi.h .
+ * Defined in: drivers/scsi/scsi_scan.c
**/
-int scsi_to_sbus_dma_dir(unsigned char scsi_data_direction)
+void scsi_scan_host(struct Scsi_Host *shost)
/**
*
* Defined in: drivers/scsi/scsi.c .
**/
-int scsi_track_queue_full(Scsi_Device *sdev, int depth)
+int scsi_track_queue_full(struct scsi_device *sdev, int depth)
/**
eh_bus_reset_handler - issue SCSI bus reset
eh_device_reset_handler - issue SCSI device reset
eh_host_reset_handler - reset host (host bus adapter)
- eh_strategy_handler - driver supplied alternate to scsi_unjam_host()
info - supply information about given host
ioctl - driver can respond to ioctls
proc_info - supports /proc/scsi/{driver_name}/{host_no}
*
* Returns SUCCESS if command aborted else FAILED
*
- * Locks: struct Scsi_Host::host_lock held (with irqsave) on entry
- * and assumed to be held on return.
+ * Locks: None held
*
* Calling context: kernel thread
*
*
* Returns SUCCESS if command aborted else FAILED
*
- * Locks: struct Scsi_Host::host_lock held (with irqsave) on entry
- * and assumed to be held on return.
+ * Locks: None held
*
* Calling context: kernel thread
*
*
* Returns SUCCESS if command aborted else FAILED
*
- * Locks: struct Scsi_Host::host_lock held (with irqsave) on entry
- * and assumed to be held on return.
+ * Locks: None held
*
* Calling context: kernel thread
*
*
* Returns SUCCESS if command aborted else FAILED
*
- * Locks: struct Scsi_Host::host_lock held (with irqsave) on entry
- * and assumed to be held on return.
+ * Locks: None held
*
* Calling context: kernel thread
*
int eh_host_reset_handler(struct scsi_cmnd * scp)
-/**
- * eh_strategy_handler - driver supplied alternate to scsi_unjam_host()
- * @shp: host on which error has occurred
- *
- * Returns TRUE if host unjammed, else FALSE.
- *
- * Locks: none
- *
- * Calling context: kernel thread
- *
- * Notes: Invoked from scsi_eh thread. LLD supplied alternate to
- * scsi_unjam_host() found in scsi_error.c
- *
- * Optionally defined in: LLD
- **/
- int eh_strategy_handler(struct Scsi_Host * shp)
-
-
/**
* info - supply information about given host: driver name plus data
* to distinguish given host
initialized from the driver's struct scsi_host_template instance. Members
of interest:
host_no - system wide unique number that is used for identifying
- this host. Issued in ascending order from 0 (and the
- positioning can be influenced by the scsihosts
- kernel boot (or module) parameter)
+ this host. Issued in ascending order from 0.
can_queue - must be greater than 0; do not send more than can_queue
commands to the adapter.
this_id - scsi id of host (scsi initiator) or -1 if not known
Each struct Scsi_Host instance has a spin_lock called struct
Scsi_Host::default_lock which is initialized in scsi_host_alloc() [found in
hosts.c]. Within the same function the struct Scsi_Host::host_lock pointer
-is initialized to point at default_lock with the scsi_assign_lock() function.
-Thereafter lock and unlock operations performed by the mid level use the
-struct Scsi_Host::host_lock pointer.
-
-LLDs can override the use of struct Scsi_Host::default_lock by
-using scsi_assign_lock(). The earliest opportunity to do this would
-be in the detect() function after it has invoked scsi_register(). It
-could be replaced by a coarser grain lock (e.g. per driver) or a
-lock of equal granularity (i.e. per host). Using finer grain locks
-(e.g. per SCSI device) may be possible by juggling locks in
-queuecommand().
+is initialized to point at default_lock. Thereafter lock and unlock
+operations performed by the mid level use the struct Scsi_Host::host_lock
+pointer. Previously drivers could override the host_lock pointer but
+this is not allowed anymore.
+
Autosense
=========
Christoph Hellwig <hch at infradead dot org>
Doug Ledford <dledford at redhat dot com>
Andries Brouwer <Andries dot Brouwer at cwi dot nl>
- Randy Dunlap <rddunlap at osdl dot org>
+ Randy Dunlap <rdunlap at xenotime dot net>
Alan Stern <stern at rowland dot harvard dot edu>
Douglas Gilbert
dgilbert at interlog dot com
-25th August 2004
+21st September 2004
git://git.onelab.eu / linux-2.6.git / blobdiff