Skip to content

L
linux
Commit ce5c5d65 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Martin K. Petersen
Browse files
Options

scsi: docs: convert scsi_mid_low_api.txt to ReST 

Link: https://lore.kernel.org/r/881e7741dfed5d6f5f73e1dfc2826b200b8604aa.1583136624.git.mchehab+huawei@kernel.orgSigned-off-by: default avatarMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent d4d79340
Show whitespace changes
Inline Side-by-side
Showing with 1337 additions and 2 deletions
Documentation/scsi/index.rst
View file @ ce5c5d65
......@@ -35,5 +35,6 @@ Linux SCSI Subsystem
scsi_eh
scsi_fc_transport
scsi-generic
scsi_mid_low_api
scsi_transport_srp/figures
Documentation/scsi/scsi_eh.rst
View file @ ce5c5d65
......@@ -5,7 +5,7 @@ SCSI EH
=======
This document describes SCSI midlayer error handling infrastructure.
Please refer to Documentation/scsi/scsi_mid_low_api.txt for more
Please refer to Documentation/scsi/scsi_mid_low_api.rst for more
information regarding SCSI midlayer.
.. TABLE OF CONTENTS
......
Documentation/scsi/scsi_mid_low_api.txt → Documentation/scsi/scsi_mid_low_api.rst
View file @ ce5c5d65
Linux Kernel 2.6 series
SCSI mid_level - lower_level driver interface
=============================================
.. SPDX-License-Identifier: GPL-2.0
=============================================
SCSI mid_level - lower_level driver interface
=============================================
Introduction
============
......@@ -84,6 +86,7 @@ IEEE 1394 connected digital cameras) that are hotplugged. Both
initialization models are discussed in the following sections.
An LLD interfaces to the SCSI subsystem several ways:
a) directly invoking functions supplied by the mid level
b) passing a set of function pointers to a registration function
supplied by the mid level. The mid level will then invoke these
......@@ -98,11 +101,11 @@ supplied functions" below.
Those functions in group b) are listed in a section entitled "Interface
functions" below. Their function pointers are placed in the members of
"struct scsi_host_template", an instance of which is passed to
scsi_host_alloc() ** . Those interface functions that the LLD does not
scsi_host_alloc() [#]_. Those interface functions that the LLD does not
wish to supply should have NULL placed in the corresponding member of
struct scsi_host_template. Defining an instance of struct
scsi_host_template at file scope will cause NULL to be placed in function
pointer members not explicitly initialized.
pointer members not explicitly initialized.
Those usages in group c) should be handled with care, especially in a
"hotplug" environment. LLDs should be aware of the lifetime of instances
......@@ -111,10 +114,10 @@ that are shared with the mid level and other layers.
All functions defined within an LLD and all data defined at file scope
should be static. For example the slave_alloc() function in an LLD
called "xxx" could be defined as
"static int xxx_slave_alloc(struct scsi_device * sdev) { /* code */ }"
``static int xxx_slave_alloc(struct scsi_device * sdev) { /* code */ }``
** the scsi_host_alloc() function is a replacement for the rather vaguely
named scsi_register() function in most situations.
.. [#] the scsi_host_alloc() function is a replacement for the rather vaguely
named scsi_register() function in most situations.
Hotplug initialization model
......@@ -137,14 +140,14 @@ aware of an LLD when that LLD registers its first HBA.
At some later time, the LLD becomes aware of an HBA and what follows
is a typical sequence of calls between the LLD and the mid level.
This example shows the mid level scanning the newly introduced HBA for 3
scsi devices of which only the first 2 respond:
scsi devices of which only the first 2 respond::
HBA PROBE: assume 2 SCSI devices found in scan
LLD mid level LLD
===-------------------=========--------------------===------
scsi_host_alloc() -->
scsi_add_host() ---->
scsi_scan_host() -------+
LLD mid level LLD
===-------------------=========--------------------===------
scsi_host_alloc() -->
scsi_add_host() ---->
scsi_scan_host() -------+
|
slave_alloc()
slave_configure() --> scsi_change_queue_depth()
......@@ -154,29 +157,28 @@ scsi_scan_host() -------+
|
slave_alloc() ***
slave_destroy() ***
------------------------------------------------------------
If the LLD wants to adjust the default queue settings, it can invoke
scsi_change_queue_depth() in its slave_configure() routine.
*** For scsi devices that the mid level tries to scan but do not
*** For scsi devices that the mid level tries to scan but do not
respond, a slave_alloc(), slave_destroy() pair is called.
If the LLD wants to adjust the default queue settings, it can invoke
scsi_change_queue_depth() in its slave_configure() routine.
When an HBA is being removed it could be as part of an orderly shutdown
associated with the LLD module being unloaded (e.g. with the "rmmod"
command) or in response to a "hot unplug" indicated by sysfs()'s
remove() callback being invoked. In either case, the sequence is the
same:
same::
HBA REMOVE: assume 2 SCSI devices attached
LLD mid level LLD
===----------------------=========-----------------===------
scsi_remove_host() ---------+
LLD mid level LLD
===----------------------=========-----------------===------
scsi_remove_host() ---------+
|
slave_destroy()
slave_destroy()
scsi_host_put()
------------------------------------------------------------
scsi_host_put()
It may be useful for a LLD to keep track of struct Scsi_Host instances
(a pointer is returned by scsi_host_alloc()). Such instances are "owned"
......@@ -193,16 +195,15 @@ The hotplug concept may be extended to SCSI devices. Currently, when an
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:
An LLD can use this sequence to make the mid level aware of a SCSI device::
SCSI DEVICE hotplug
LLD mid level LLD
===-------------------=========--------------------===------
scsi_add_device() ------+
LLD mid level LLD
===-------------------=========--------------------===------
scsi_add_device() ------+
|
slave_alloc()
slave_configure() [--> scsi_change_queue_depth()]
------------------------------------------------------------
In a similar fashion, an LLD may become aware that a SCSI device has been
removed (unplugged) or the connection to it has been interrupted. Some
......@@ -210,15 +211,14 @@ existing SCSI transports (e.g. SPI) may not become aware that a SCSI
device has been removed until a subsequent SCSI command fails which will
probably cause that device to be set offline by the mid level. An LLD that
detects the removal of a SCSI device can instigate its removal from
upper layers with this sequence:
upper layers with this sequence::
SCSI DEVICE hot unplug
LLD mid level LLD
===----------------------=========-----------------===------
scsi_remove_device() -------+
LLD mid level LLD
===----------------------=========-----------------===------
scsi_remove_device() -------+
|
slave_destroy()
------------------------------------------------------------
It may be useful for an LLD to keep track of struct scsi_device instances
(a pointer is passed as the parameter to slave_alloc() and
......@@ -237,10 +237,16 @@ where they do.
There are 3 reference counting functions of interest associated with
struct Scsi_Host:
- scsi_host_alloc(): returns a pointer to new instance of struct
- scsi_host_alloc():
returns a pointer to new instance of struct
Scsi_Host which has its reference count ^^ set to 1
- scsi_host_get(): adds 1 to the reference count of the given instance
- scsi_host_put(): decrements 1 from the reference count of the given
- scsi_host_get():
adds 1 to the reference count of the given instance
- scsi_host_put():
decrements 1 from the reference count of the given
instance. If the reference count reaches 0 then the given instance
is freed
......@@ -254,8 +260,10 @@ to bump its reference count. When it is finished with the pointer it can
use scsi_device_put() to decrement its reference count (and potentially
delete it).
^^ struct Scsi_Host actually has 2 reference counts which are manipulated
in parallel by these functions.
.. Note::
struct Scsi_Host actually has 2 reference counts which are manipulated
in parallel by these functions.
Conventions
......@@ -273,7 +281,7 @@ Also, most C99 enhancements are encouraged to the extent they are supported
by the relevant gcc compilers. So C99 style structure and array
initializers are encouraged where appropriate. Don't go too far,
VLAs are not properly supported yet. An exception to this is the use of
"//" style comments; /*...*/ comments are still preferred in Linux.
``//`` style comments; ``/*...*/`` comments are still preferred in Linux.
Well written, tested and documented code, need not be re-formatted to
comply with the above conventions. For example, the aic7xxx driver
......@@ -288,31 +296,32 @@ 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_".
names all start with ``scsi_``.
Summary:
scsi_add_device - creates new scsi device (lu) instance
scsi_add_host - perform sysfs registration and set up transport class
scsi_change_queue_depth - change the queue depth on a SCSI device
scsi_bios_ptable - return copy of block device's partition table
scsi_block_requests - prevent further commands being queued to given host
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_partsize - parse partition table into cylinders, heads + sectors
scsi_register - create and register a scsi host adapter instance.
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_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_add_device - creates new scsi device (lu) instance
- scsi_add_host - perform sysfs registration and set up transport class
- scsi_change_queue_depth - change the queue depth on a SCSI device
- scsi_bios_ptable - return copy of block device's partition table
- scsi_block_requests - prevent further commands being queued to given host
- 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_partsize - parse partition table into cylinders, heads + sectors
- scsi_register - create and register a scsi host adapter instance.
- 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_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_add_device - creates new scsi device (lu) instance
* @shost: pointer to scsi host instance
* @channel: channel number (rarely other than 0)
......@@ -334,12 +343,12 @@ Details:
*
* Defined in: drivers/scsi/scsi_scan.c
**/
struct scsi_device * scsi_add_device(struct Scsi_Host *shost,
struct scsi_device * scsi_add_device(struct Scsi_Host *shost,
unsigned int channel,
unsigned int id, unsigned int lun)
/**
/**
* 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
......@@ -357,10 +366,10 @@ struct scsi_device * scsi_add_device(struct Scsi_Host *shost,
*
* Defined in: drivers/scsi/hosts.c
**/
int scsi_add_host(struct Scsi_Host *shost, struct device * dev)
int scsi_add_host(struct Scsi_Host *shost, struct device * dev)
/**
/**
* scsi_change_queue_depth - allow LLD to change queue depth on a SCSI device
* @sdev: pointer to SCSI device to change queue depth on
* @tags Number of tags allowed if tagged queuing enabled,
......@@ -378,10 +387,10 @@ int scsi_add_host(struct Scsi_Host *shost, struct device * dev)
* Defined in: drivers/scsi/scsi.c [see source code for more notes]
*
**/
int scsi_change_queue_depth(struct scsi_device *sdev, int tags)
int scsi_change_queue_depth(struct scsi_device *sdev, int tags)
/**
/**
* scsi_bios_ptable - return copy of block device's partition table
* @dev: pointer to block device
*
......@@ -393,10 +402,10 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int tags)
*
* Defined in: drivers/scsi/scsicam.c
**/
unsigned char *scsi_bios_ptable(struct block_device *dev)
unsigned char *scsi_bios_ptable(struct block_device *dev)
/**
/**
* scsi_block_requests - prevent further commands being queued to given host
*
* @shost: pointer to host to block commands on
......@@ -409,11 +418,11 @@ unsigned char *scsi_bios_ptable(struct block_device *dev)
* get unblocked other than the LLD calling scsi_unblock_requests().
*
* Defined in: drivers/scsi/scsi_lib.c
**/
void scsi_block_requests(struct Scsi_Host * shost)
**/
void scsi_block_requests(struct Scsi_Host * shost)
/**
/**
* scsi_host_alloc - create a scsi host adapter instance and perform basic
* initialization.
* @sht: pointer to scsi host template
......@@ -434,11 +443,11 @@ void scsi_block_requests(struct Scsi_Host * shost)
*
* Defined in: drivers/scsi/hosts.c .
**/
struct Scsi_Host * scsi_host_alloc(struct scsi_host_template * sht,
struct Scsi_Host * scsi_host_alloc(struct scsi_host_template * sht,
int privsize)
/**
/**
* scsi_host_get - increment Scsi_Host instance refcount
* @shost: pointer to struct Scsi_Host instance
*
......@@ -450,10 +459,10 @@ struct Scsi_Host * scsi_host_alloc(struct scsi_host_template * sht,
*
* Defined in: drivers/scsi/hosts.c
**/
void scsi_host_get(struct Scsi_Host *shost)
void scsi_host_get(struct Scsi_Host *shost)
/**
/**
* scsi_host_put - decrement Scsi_Host instance refcount, free if 0
* @shost: pointer to struct Scsi_Host instance
*
......@@ -469,10 +478,10 @@ void scsi_host_get(struct Scsi_Host *shost)
*
* Defined in: drivers/scsi/hosts.c
**/
void scsi_host_put(struct Scsi_Host *shost)
void scsi_host_put(struct Scsi_Host *shost)
/**
/**
* scsi_partsize - parse partition table into cylinders, heads + sectors
* @buf: pointer to partition table
* @capacity: size of (total) disk in 512 byte sectors
......@@ -488,11 +497,11 @@ void scsi_host_put(struct Scsi_Host *shost)
*
* Defined in: drivers/scsi/scsicam.c
**/
int scsi_partsize(unsigned char *buf, unsigned long capacity,
int scsi_partsize(unsigned char *buf, unsigned long capacity,
unsigned int *cyls, unsigned int *hds, unsigned int *secs)
/**
/**
* scsi_register - create and register a scsi host adapter instance.
* @sht: pointer to scsi host template
* @privsize: extra bytes to allocate in hostdata array (which is the
......@@ -509,11 +518,11 @@ int scsi_partsize(unsigned char *buf, unsigned long capacity,
*
* Defined in: drivers/scsi/hosts.c .
**/
struct Scsi_Host * scsi_register(struct scsi_host_template * sht,
struct Scsi_Host * scsi_register(struct scsi_host_template * sht,
int privsize)
/**
/**
* scsi_remove_device - detach and remove a SCSI device
* @sdev: a pointer to a scsi device instance
*
......@@ -529,10 +538,10 @@ struct Scsi_Host * scsi_register(struct scsi_host_template * sht,
*
* Defined in: drivers/scsi/scsi_sysfs.c .
**/
int scsi_remove_device(struct scsi_device *sdev)
int scsi_remove_device(struct scsi_device *sdev)
/**
/**
* scsi_remove_host - detach and remove all SCSI devices owned by host
* @shost: a pointer to a scsi host instance
*
......@@ -546,10 +555,10 @@ int scsi_remove_device(struct scsi_device *sdev)
*
* Defined in: drivers/scsi/hosts.c .
**/
int scsi_remove_host(struct Scsi_Host *shost)
int scsi_remove_host(struct Scsi_Host *shost)
/**
/**
* scsi_report_bus_reset - report scsi _bus_ reset observed
* @shost: a pointer to a scsi host involved
* @channel: channel (within) host on which scsi bus reset occurred
......@@ -566,10 +575,10 @@ int scsi_remove_host(struct Scsi_Host *shost)
*
* Defined in: drivers/scsi/scsi_error.c .
**/
void scsi_report_bus_reset(struct Scsi_Host * shost, int channel)
void scsi_report_bus_reset(struct Scsi_Host * shost, int channel)
/**
/**
* scsi_scan_host - scan SCSI bus
* @shost: a pointer to a scsi host instance
*
......@@ -579,10 +588,10 @@ void scsi_report_bus_reset(struct Scsi_Host * shost, int channel)
*
* Defined in: drivers/scsi/scsi_scan.c
**/
void scsi_scan_host(struct Scsi_Host *shost)
void scsi_scan_host(struct Scsi_Host *shost)
/**
/**
* scsi_track_queue_full - track successive QUEUE_FULL events on given
* device to determine if and when there is a need
* to adjust the queue depth on the device.
......@@ -602,10 +611,10 @@ void scsi_scan_host(struct Scsi_Host *shost)
*
* Defined in: drivers/scsi/scsi.c .
**/
int scsi_track_queue_full(struct scsi_device *sdev, int depth)
int scsi_track_queue_full(struct scsi_device *sdev, int depth)
/**
/**
* scsi_unblock_requests - allow further commands to be queued to given host
*
* @shost: pointer to host to unblock commands on
......@@ -615,11 +624,11 @@ int scsi_track_queue_full(struct scsi_device *sdev, int depth)
* Might block: no
*
* Defined in: drivers/scsi/scsi_lib.c .
**/
void scsi_unblock_requests(struct Scsi_Host * shost)
**/
void scsi_unblock_requests(struct Scsi_Host * shost)
/**
/**
* scsi_unregister - unregister and free memory used by host instance
* @shp: pointer to scsi host instance to unregister.
*
......@@ -634,7 +643,7 @@ void scsi_unblock_requests(struct Scsi_Host * shost)
*
* Defined in: drivers/scsi/hosts.c .
**/
void scsi_unregister(struct Scsi_Host * shp)
void scsi_unregister(struct Scsi_Host * shp)
......@@ -646,8 +655,10 @@ pointers are placed in an instance of struct scsi_host_template which
is passed to scsi_host_alloc() [or scsi_register() / init_this_scsi_driver()].
Some are mandatory. Interface functions should be declared static. The
accepted convention is that driver "xyz" will declare its slave_configure()
function as:
function as::
static int xyz_slave_configure(struct scsi_device * sdev);
and so forth for all interface functions listed below.
A pointer to this function should be placed in the 'slave_configure' member
......@@ -662,24 +673,25 @@ In some cases more detail is given in scsi_host.h than below.
The interface functions are listed below in alphabetical order.
Summary:
bios_param - fetch head, sector, cylinder info for a disk
eh_timed_out - notify the host that a command timer expired
eh_abort_handler - abort given command
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)
info - supply information about given host
ioctl - driver can respond to ioctls
proc_info - supports /proc/scsi/{driver_name}/{host_no}
queuecommand - queue scsi command, invoke 'done' on completion
slave_alloc - prior to any commands being sent to a new device
slave_configure - driver fine tuning for given device after attach
slave_destroy - given device is about to be shut down
Details:
/**
- bios_param - fetch head, sector, cylinder info for a disk
- eh_timed_out - notify the host that a command timer expired
- eh_abort_handler - abort given command
- 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)
- info - supply information about given host
- ioctl - driver can respond to ioctls
- proc_info - supports /proc/scsi/{driver_name}/{host_no}
- queuecommand - queue scsi command, invoke 'done' on completion
- slave_alloc - prior to any commands being sent to a new device
- slave_configure - driver fine tuning for given device after attach
- slave_destroy - given device is about to be shut down
Details::
/**
* bios_param - fetch head, sector, cylinder info for a disk
* @sdev: pointer to scsi device context (defined in
* include/scsi/scsi_device.h)
......@@ -707,7 +719,7 @@ Details:
sector_t capacity, int params[3])
/**
/**
* eh_timed_out - The timer for the command has just fired
* @scp: identifies command timing out
*
......@@ -733,7 +745,7 @@ Details:
int eh_timed_out(struct scsi_cmnd * scp)
/**
/**
* eh_abort_handler - abort command associated with scp
* @scp: identifies command to be aborted
*
......@@ -754,7 +766,7 @@ Details:
int eh_abort_handler(struct scsi_cmnd * scp)
/**
/**
* eh_bus_reset_handler - issue SCSI bus reset
* @scp: SCSI bus that contains this device should be reset
*
......@@ -772,7 +784,7 @@ Details:
int eh_bus_reset_handler(struct scsi_cmnd * scp)
/**
/**
* eh_device_reset_handler - issue SCSI device reset
* @scp: identifies SCSI device to be reset
*
......@@ -790,7 +802,7 @@ Details:
int eh_device_reset_handler(struct scsi_cmnd * scp)
/**
/**
* eh_host_reset_handler - reset host (host bus adapter)
* @scp: SCSI host that contains this device should be reset
*
......@@ -812,7 +824,7 @@ Details:
int eh_host_reset_handler(struct scsi_cmnd * scp)
/**
/**
* info - supply information about given host: driver name plus data
* to distinguish given host
* @shp: host to supply information about
......@@ -842,7 +854,7 @@ Details:
const char * info(struct Scsi_Host * shp)
/**
/**
* ioctl - driver can respond to ioctls
* @sdp: device that ioctl was issued for
* @cmd: ioctl number
......@@ -871,7 +883,7 @@ Details:
int ioctl(struct scsi_device *sdp, int cmd, void *arg)
/**
/**
* proc_info - supports /proc/scsi/{driver_name}/{host_no}
* @buffer: anchor point to output to (0==writeto1_read0) or fetch from
* (1==writeto1_read0).
......@@ -902,7 +914,7 @@ Details:
int length, int host_no, int writeto1_read0)
/**
/**
* queuecommand - queue scsi command, invoke scp->scsi_done on completion
* @shost: pointer to the scsi host object
* @scp: pointer to scsi command object
......@@ -974,7 +986,7 @@ Details:
int queuecommand(struct Scsi_Host *shost, struct scsi_cmnd * scp)
/**
/**
* slave_alloc - prior to any commands being sent to a new device
* (i.e. just prior to scan) this call is made
* @sdp: pointer to new device (about to be scanned)
......@@ -999,7 +1011,7 @@ Details:
int slave_alloc(struct scsi_device *sdp)
/**
/**
* slave_configure - driver fine tuning for given device just after it
* has been first scanned (i.e. it responded to an
* INQUIRY)
......@@ -1022,7 +1034,7 @@ Details:
int slave_configure(struct scsi_device *sdp)
/**
/**
* slave_destroy - given device is about to be shut down. All
* activity has ceased on this device.
* @sdp: device that is about to be shut down
......@@ -1051,21 +1063,28 @@ Data Structures
===============
struct scsi_host_template
-------------------------
There is one "struct scsi_host_template" instance per LLD ***. It is
There is one "struct scsi_host_template" instance per LLD [#]_. It is
typically initialized as a file scope static in a driver's header file. That
way members that are not explicitly initialized will be set to 0 or NULL.
Member of interest:
name - name of driver (may contain spaces, please limit to
name
- name of driver (may contain spaces, please limit to
less than 80 characters)
proc_name - name used in "/proc/scsi/<proc_name>/<host_no>" and
proc_name
- name used in "/proc/scsi/<proc_name>/<host_no>" and
by sysfs in one of its "drivers" directories. Hence
"proc_name" should only contain characters acceptable
to a Unix file name.
(*queuecommand)() - primary callback that the mid level uses to inject
``(*queuecommand)()``
- primary callback that the mid level uses to inject
SCSI commands into an LLD.
The structure is defined and commented in include/scsi/scsi_host.h
*** In extreme situations a single driver may have several instances
.. [#] In extreme situations a single driver may have several instances
if it controls several different classes of hardware (e.g. an LLD
that handles both ISA and PCI cards and has a separate instance of
struct scsi_host_template for each class).
......@@ -1078,42 +1097,58 @@ with "struct scsi_host_template". When a new struct Scsi_Host instance
is created (in scsi_host_alloc() in hosts.c) those common members are
initialized from the driver's struct scsi_host_template instance. Members
of interest:
host_no - system wide unique number that is used for identifying
host_no
- system wide unique number that is used for identifying
this host. Issued in ascending order from 0.
can_queue - must be greater than 0; do not send more than can_queue
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
sg_tablesize - maximum scatter gather elements allowed by host.
this_id
- scsi id of host (scsi initiator) or -1 if not known
sg_tablesize
- maximum scatter gather elements allowed by host.
Set this to SG_ALL or less to avoid chained SG lists.
Must be at least 1.
max_sectors - maximum number of sectors (usually 512 bytes) allowed
max_sectors
- maximum number of sectors (usually 512 bytes) allowed
in a single SCSI command. The default value of 0 leads
to a setting of SCSI_DEFAULT_MAX_SECTORS (defined in
scsi_host.h) which is currently set to 1024. So for a
disk the maximum transfer size is 512 KB when max_sectors
is not defined. Note that this size may not be sufficient
for disk firmware uploads.
cmd_per_lun - maximum number of commands that can be queued on devices
cmd_per_lun
- maximum number of commands that can be queued on devices
controlled by the host. Overridden by LLD calls to
scsi_change_queue_depth().
unchecked_isa_dma - 1=>only use bottom 16 MB of ram (ISA DMA addressing
unchecked_isa_dma
- 1=>only use bottom 16 MB of ram (ISA DMA addressing
restriction), 0=>can use full 32 bit (or better) DMA
address space
no_async_abort - 1=>Asynchronous aborts are not supported
0=>Timed-out commands will be aborted asynchronously
hostt - pointer to driver's struct scsi_host_template from which
no_async_abort
- 1=>Asynchronous aborts are not supported
- 0=>Timed-out commands will be aborted asynchronously
hostt
- pointer to driver's struct scsi_host_template from which
this struct Scsi_Host instance was spawned
hostt->proc_name - name of LLD. This is the driver name that sysfs uses
transportt - pointer to driver's struct scsi_transport_template instance
hostt->proc_name
- name of LLD. This is the driver name that sysfs uses
transportt
- pointer to driver's struct scsi_transport_template instance
(if any). FC and SPI transports currently supported.
sh_list - a double linked list of pointers to all struct Scsi_Host
sh_list
- a double linked list of pointers to all struct Scsi_Host
instances (currently ordered by ascending host_no)
my_devices - a double linked list of pointers to struct scsi_device
my_devices
- a double linked list of pointers to struct scsi_device
instances that belong to this host.
hostdata[0] - area reserved for LLD at end of struct Scsi_Host. Size
hostdata[0]
- area reserved for LLD at end of struct Scsi_Host. Size
is set by the second argument (named 'xtr_bytes') to
scsi_host_alloc() or scsi_register().
vendor_id - a unique value that identifies the vendor supplying
vendor_id
- a unique value that identifies the vendor supplying
the LLD for the Scsi_Host. Used most often in validating
vendor-specific message requests. Value consists of an
identifier type and a vendor-specific value.
......@@ -1136,26 +1171,35 @@ commands become queued against the LLD than are indicated by
scsi_change_queue_depth() (or struct Scsi_Host::cmd_per_lun). There will
be at least one instance of struct scsi_cmnd available for each SCSI device.
Members of interest:
cmnd - array containing SCSI command
cmnd_len - length (in bytes) of SCSI command
sc_data_direction - direction of data transfer in data phase. See
cmnd
- array containing SCSI command
cmnd_len
- length (in bytes) of SCSI command
sc_data_direction
- direction of data transfer in data phase. See
"enum dma_data_direction" in include/linux/dma-mapping.h
request_bufflen - number of data bytes to transfer (0 if no data phase)
use_sg - ==0 -> no scatter gather list, hence transfer data
request_bufflen
- number of data bytes to transfer (0 if no data phase)
use_sg
- ==0 -> no scatter gather list, hence transfer data
to/from request_buffer
- >0 -> scatter gather list (actually an array) in
request_buffer with use_sg elements
request_buffer - either contains data buffer or scatter gather list
request_buffer
- either contains data buffer or scatter gather list
depending on the setting of use_sg. Scatter gather
elements are defined by 'struct scatterlist' found
in include/linux/scatterlist.h .
done - function pointer that should be invoked by LLD when the
done
- function pointer that should be invoked by LLD when the
SCSI command is completed (successfully or otherwise).
Should only be called by an LLD if the LLD has accepted
the command (i.e. queuecommand() returned or will return
0). The LLD may invoke 'done' prior to queuecommand()
finishing.
result - should be set by LLD prior to calling 'done'. A value
result
- should be set by LLD prior to calling 'done'. A value
of 0 implies a successfully completed command (and all
data (if any) has been transferred to or from the SCSI
target device). 'result' is a 32 bit unsigned integer that
......@@ -1163,7 +1207,8 @@ Members of interest:
in the LSB. See include/scsi/scsi.h status_byte(),
msg_byte(), host_byte() and driver_byte() macros and
related constants.
sense_buffer - an array (maximum size: SCSI_SENSE_BUFFERSIZE bytes) that
sense_buffer
- an array (maximum size: SCSI_SENSE_BUFFERSIZE bytes) that
should be written when the SCSI status (LSB of 'result')
is set to CHECK_CONDITION (2). When CHECK_CONDITION is
set, if the top nibble of sense_buffer[0] has the value 7
......@@ -1173,9 +1218,11 @@ Members of interest:
retrieve the sense buffer. The latter strategy is error
prone in the presence of command queuing so the LLD should
always "auto-sense".
device - pointer to scsi_device object that this command is
device
- pointer to scsi_device object that this command is
associated with.
resid - an LLD should set this signed integer to the requested
resid
- an LLD should set this signed integer to the requested
transfer length (i.e. 'request_bufflen') less the number
of bytes that are actually transferred. 'resid' is
preset to 0 so an LLD can ignore it if it cannot detect
......@@ -1183,7 +1230,8 @@ Members of interest:
should set 'resid' prior to invoking 'done'. The most
interesting case is data transfers from a SCSI target
device (e.g. READs) that underrun.
underflow - LLD should place (DID_ERROR << 16) in 'result' if
underflow
- LLD should place (DID_ERROR << 16) in 'result' if
actual number of bytes transferred is less than this
figure. Not many LLDs implement this check and some that
do just output an error message to the log rather than
......@@ -1196,10 +1244,13 @@ when such data transfers have sense keys of MEDIUM ERROR and HARDWARE ERROR
(and possibly RECOVERED ERROR). In these cases if a LLD is in doubt how much
data has been received then the safest approach is to indicate no bytes have
been received. For example: to indicate that no valid data has been received
a LLD might use these helpers:
a LLD might use these helpers::
scsi_set_resid(SCpnt, scsi_bufflen(SCpnt));
where 'SCpnt' is a pointer to a scsi_cmnd object. To indicate only three 512
bytes blocks has been received 'resid' could be set like this:
bytes blocks has been received 'resid' could be set like this::
scsi_set_resid(SCpnt, scsi_bufflen(SCpnt) - (3 * 512));
The scsi_cmnd structure is defined in include/scsi/scsi_cmnd.h
......@@ -1223,6 +1274,7 @@ automatic return of sense data to the application client coincident
with the completion of a SCSI command" when a status of CHECK CONDITION
occurs. LLDs should perform autosense. This should be done when the LLD
detects a CHECK CONDITION status by either:
a) instructing the SCSI protocol (e.g. SCSI Parallel Interface (SPI))
to perform an extra data in phase on such responses
b) or, the LLD issuing a REQUEST SENSE command itself
......@@ -1265,16 +1317,18 @@ to support it.
Credits
=======
The following people have contributed to this document:
Mike Anderson <andmike at us dot ibm dot com>
James Bottomley <James dot Bottomley at hansenpartnership dot com>
Patrick Mansfield <patmans at us dot ibm dot com>
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 <rdunlap at xenotime dot net>
Alan Stern <stern at rowland dot harvard dot edu>
- Mike Anderson <andmike at us dot ibm dot com>
- James Bottomley <James dot Bottomley at hansenpartnership dot com>
- Patrick Mansfield <patmans at us dot ibm dot com>
- 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 <rdunlap at xenotime dot net>
- Alan Stern <stern at rowland dot harvard dot edu>
Douglas Gilbert
dgilbert at interlog dot com
21st September 2004
scripts/documentation-file-ref-check
View file @ ce5c5d65
......@@ -12,7 +12,7 @@ use Getopt::Long qw(:config no_auto_abbrev);
# to mention a past documentation file, for example, to give credits for
# the original work.
my %false_positives = (
"Documentation/scsi/scsi_mid_low_api.txt" => "Documentation/Configure.help",
"Documentation/scsi/scsi_mid_low_api.rst" => "Documentation/Configure.help",
"drivers/vhost/vhost.c" => "Documentation/virtual/lguest/lguest.c",
);
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7