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
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_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_deactivate_tcq - turn off tag command queueing
scsi_delete_timer - cancel timer on a SCSI command.
scsi_host_alloc - return a new scsi_host instance whose refcount==1
scsi_host_get - increments Scsi_Host instance's refcount
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
/**
- * 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]
*
void scsi_block_requests(struct Scsi_Host * shost)
+/**
+ * scsi_deactivate_tcq - turn off tag command queueing
+ * @sdev: device to turn off TCQ for
+ * @depth: queue depth (stored in sdev)
+ *
+ * Returns nothing
+ *
+ * Might block: no
+ *
+ * Defined (inline) in: include/scsi/scsi_tcq.h
+ **/
+void scsi_deactivate_tcq(struct scsi_device *sdev, int depth)
+
+
/**
* scsi_delete_timer - cancel timer on a SCSI command.
* @scmd: pointer to scsi command instance
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
Douglas Gilbert
dgilbert at interlog dot com
-25th August 2004
+21st September 2004
git://git.onelab.eu / linux-2.6.git / blobdiff