freebsd-skq/lib/libcam/cam_cdbparse.3

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.\" Copyright (c) 1998 Kenneth D. Merry.
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL HD ASSOCIATES OR CONTRIBUTORS BE LIABLE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.Dd March 13, 2017
.Dt CAM_CDBPARSE 3
.Os
.Sh NAME
.Nm csio_build ,
.Nm csio_build_visit ,
.Nm csio_decode ,
.Nm csio_decode_visit ,
.Nm buff_decode ,
.Nm buff_decode_visit ,
.Nm csio_encode ,
.Nm csio_encode_visit ,
.Nm buff_encode_visit
.Nd CAM user library SCSI buffer parsing routines
.Sh LIBRARY
.Lb libcam
.Sh SYNOPSIS
.In stdio.h
.In camlib.h
.Ft int
.Fo csio_build
.Fa "struct ccb_scsiio *csio"
.Fa "uint8_t *data_ptr"
.Fa "uint32_t dxfer_len"
.Fa "uint32_t flags"
.Fa "int retry_count"
.Fa "int timeout"
.Fa "const char *cmd_spec"
.Fa "..."
.Fc
.Ft int
.Fo csio_build_visit
.Fa "struct ccb_scsiio *csio"
.Fa "uint8_t *data_ptr"
.Fa "uint32_t dxfer_len"
.Fa "uint32_t flags"
.Fa "int retry_count"
.Fa "int timeout"
.Fa "const char *cmd_spec"
.Fa "int (*arg_get)(void *hook, char *field_name)"
.Fa "void *gethook"
.Fc
.Ft int
.Fo csio_decode
.Fa "struct ccb_scsiio *csio"
.Fa "const char *fmt"
.Fa "..."
.Fc
.Ft int
.Fo csio_decode_visit
.Fa "struct ccb_scsiio *csio"
.Fa "const char *fmt"
.Fa "void (*arg_put)(void *hook"
.Fa "int letter"
.Fa "void *val"
.Fa "int count"
.Fa "char *name)"
.Fa "void *puthook"
.Fc
.Ft int
.Fo buff_decode
.Fa "uint8_t *buff"
.Fa "size_t len"
.Fa "const char *fmt"
.Fa "..."
.Fc
.Ft int
.Fo buff_decode_visit
.Fa "uint8_t *buff"
.Fa "size_t len"
.Fa "const char *fmt"
.Fa "void (*arg_put)(void *, int, void *, int, char *)"
.Fa "void *puthook"
.Fc
.Ft int
.Fo csio_encode
.Fa "struct ccb_scsiio *csio"
.Fa "const char *fmt"
.Fa "..."
.Fc
.Ft int
.Fo csio_encode_visit
.Fa "struct ccb_scsiio *csio"
.Fa "const char *fmt"
.Fa "int (*arg_get)(void *hook, char *field_name)"
.Fa "void *gethook"
.Fc
.Ft int
.Fo buff_encode_visit
.Fa "uint8_t *buff"
.Fa "size_t len"
.Fa "const char *fmt"
.Fa "int (*arg_get)(void *hook, char *field_name)"
.Fa "void *gethook"
.Fc
.Sh DESCRIPTION
The CAM buffer/CDB encoding and decoding routines provide a relatively easy
migration path for userland
.Tn SCSI
applications written with the similarly-named
.Va scsireq_ Ns *
functions from the old
.Fx
.Tn SCSI
layer.
.Pp
These functions may be used in new applications, but users may find it
easier to use the various SCSI CCB building functions included with the
.Xr cam 3
library, e.g., \&
.Fn cam_fill_csio ,
.Fn scsi_start_stop ,
and
.Fn scsi_read_write .
.Pp
.Fn csio_build
builds up a
.Va ccb_scsiio
structure based on the information provided in
the variable argument list.
It gracefully handles a NULL
.Fa data_ptr
argument passed to it.
.Pp
.Fa dxfer_len
is the length of the data phase; the data transfer direction is
determined by the
.Fa flags
argument.
.Pp
.Fa data_ptr
is the data buffer used during the
.Tn SCSI
data phase.
If no data is to be
transferred for the
.Tn SCSI
command in question, this should be set to NULL.
If there is data to
transfer for the command, this buffer must be at least
.Fa dxfer_len
long.
.Pp
.Fa flags
are the flags defined in
.In cam/cam_ccb.h :
.Bd -literal
/* Common CCB header */
/* CAM CCB flags */
typedef enum {
     CAM_CDB_POINTER       = 0x00000001,/* The CDB field is a pointer    */
     CAM_QUEUE_ENABLE      = 0x00000002,/* SIM queue actions are enabled */
     CAM_CDB_LINKED        = 0x00000004,/* CCB contains a linked CDB     */
     CAM_SCATTER_VALID     = 0x00000010,/* Scatter/gather list is valid  */
     CAM_DIS_AUTOSENSE     = 0x00000020,/* Disable autosense feature     */
     CAM_DIR_RESV          = 0x00000000,/* Data direction (00:reserved)  */
     CAM_DIR_IN            = 0x00000040,/* Data direction (01:DATA IN)   */
     CAM_DIR_OUT           = 0x00000080,/* Data direction (10:DATA OUT)  */
     CAM_DIR_NONE          = 0x000000C0,/* Data direction (11:no data)   */
     CAM_DIR_MASK          = 0x000000C0,/* Data direction Mask		 */
     CAM_SOFT_RST_OP       = 0x00000100,/* Use Soft reset alternative    */
     CAM_ENG_SYNC          = 0x00000200,/* Flush resid bytes on complete */
     CAM_DEV_QFRZDIS       = 0x00000400,/* Disable DEV Q freezing	 */
     CAM_DEV_QFREEZE       = 0x00000800,/* Freeze DEV Q on execution     */
     CAM_HIGH_POWER        = 0x00001000,/* Command takes a lot of power  */
     CAM_SENSE_PTR         = 0x00002000,/* Sense data is a pointer	 */
     CAM_SENSE_PHYS        = 0x00004000,/* Sense pointer is physical addr*/
     CAM_TAG_ACTION_VALID  = 0x00008000,/* Use the tag action in this ccb*/
     CAM_PASS_ERR_RECOVER  = 0x00010000,/* Pass driver does err. recovery*/
     CAM_DIS_DISCONNECT    = 0x00020000,/* Disable disconnect		 */
     CAM_SG_LIST_PHYS      = 0x00040000,/* SG list has physical addrs.   */
     CAM_MSG_BUF_PHYS      = 0x00080000,/* Message buffer ptr is physical*/
     CAM_SNS_BUF_PHYS      = 0x00100000,/* Autosense data ptr is physical*/
     CAM_DATA_PHYS         = 0x00200000,/* SG/Buffer data ptrs are phys. */
     CAM_CDB_PHYS          = 0x00400000,/* CDB pointer is physical	 */
     CAM_ENG_SGLIST        = 0x00800000,/* SG list is for the HBA engine */

/* Phase cognizant mode flags */
     CAM_DIS_AUTOSRP       = 0x01000000,/* Disable autosave/restore ptrs */
     CAM_DIS_AUTODISC      = 0x02000000,/* Disable auto disconnect	 */
     CAM_TGT_CCB_AVAIL     = 0x04000000,/* Target CCB available		 */
     CAM_TGT_PHASE_MODE    = 0x08000000,/* The SIM runs in phase mode	 */
     CAM_MSGB_VALID        = 0x20000000,/* Message buffer valid		 */
     CAM_STATUS_VALID      = 0x40000000,/* Status buffer valid		 */
     CAM_DATAB_VALID       = 0x80000000,/* Data buffer valid		 */

/* Host target Mode flags */
     CAM_TERM_IO           = 0x20000000,/* Terminate I/O Message sup.    */
     CAM_DISCONNECT        = 0x40000000,/* Disconnects are mandatory     */
     CAM_SEND_STATUS       = 0x80000000,/* Send status after data phase  */
} ccb_flags;
.Ed
.Pp
Multiple flags should be ORed together.
Any of the CCB flags may be used,
although it is worth noting several important ones here:
.Bl -tag -width CAM_PASS_ERR_RECOVER
.It Dv CAM_DIR_IN
This indicates that the operation in question is a read operation.
i.e.,
data is being read from the
.Tn SCSI
device to the user-supplied buffer.
.It Dv CAM_DIR_OUT
This indicates that the operation is a write operation.
i.e., data is being
written from the user-supplied buffer to the device.
.It Dv CAM_DIR_NONE
This indicates that there is no data to be transferred for this command.
.It Dv CAM_DEV_QFRZDIS
This flag disables device queue freezing as an error recovery mechanism.
.It Dv CAM_PASS_ERR_RECOVER
This flag tells the
.Xr pass 4
driver to enable error recovery.
The default is to not perform error
recovery, which means that the retry count will not be honored without this
flag, among other things.
.It Dv CAM_DATA_PHYS
This indicates that the address contained in
.Fa data_ptr
is a physical address, not a virtual address.
.El
.Pp
The
.Fa retry_count
tells the kernel how many times to retry the command in question.
The
retry count is ignored unless the
.Xr pass 4
driver is told to enable error recovery via the
.Dv CAM_PASS_ERR_RECOVER
flag.
.Pp
The
.Fa timeout
tells the kernel how long to wait for the given command to complete.
If
the timeout expires and the command has not completed, the CCB will be
returned from the kernel with an appropriate error status.
.Pp
.Fa cmd_spec
is a CDB format specifier used to build up the SCSI CDB.
This text string is made up of a list of field specifiers.
Field
specifiers specify the value for each CDB field (including indicating
that the value be taken from the next argument in the
variable argument list), the width
of the field in bits or bytes, and an optional name.
White space is
ignored, and the pound sign ('#') introduces a comment that ends at the
end of the current line.
.Pp
The optional name is the first part of a field specifier and
is in curly braces.
The text in curly braces in this example are
the names:
.Dl "{PS} v:b1 {Reserved} 0:b1 {Page Code} v:b6 # Mode select page"
.Pp
This field specifier has two one bit fields and one six bit field.
The second one bit field is the constant value 0 and the first
one bit field and the six bit field are taken from the variable
argument list.
Multi byte fields are swapped into the SCSI byte order in the
CDB and white space is ignored.
.Pp
When the field is a hex value or the letter v, (e.g.,
.Fa "1A"
or
.Fa "v" )
then a single byte value
is copied to the next unused byte of the CDB.
When the letter
.Fa v
is used the next integer argument is taken from the variable argument list
and that value used.
.Pp
A constant hex value followed by a field width specifier or the letter
.Fa v
followed by a field width specifier (e.g.,
.Fa 3:4 ,
.Fa 3:b4 ,
.Fa 3:i3 ,
.Fa v:i3 )
specifies a field of a given bit or byte width.
Either the constant value or (for the V specifier) the next integer value from
the variable argument list is copied to the next unused
bits or bytes of the CDB.
.Pp
A decimal number or the letter
.Fa b
followed by a decimal number field width indicates a bit field of that width.
The bit fields are packed as tightly as possible beginning with the
high bit (so that it reads the same as the SCSI spec), and a new byte of
the CDB is started whenever a byte fills completely or when an
.Fa i
field is encountered.
.Pp
A field width specifier consisting of the letter
.Fa i
followed by either
1, 2, 3 or 4 indicates a 1, 2, 3 or 4 byte integral value that must
be swapped into SCSI byte order (MSB first).
.Pp
For the
.Fa v
field specifier the next integer argument is taken from the variable argument
list and that value is used swapped into SCSI byte order.
.Pp
.Fn csio_build_visit
operates similarly to
.Fn csio_build ,
except that the values to substitute for variable arguments in
.Fa cmd_spec
are retrieved via the
.Fn arg_get
function passed in to
.Fn csio_build_visit
instead of via
.Xr stdarg 3 .
The
.Fn arg_get
function takes two arguments:
.Bl -tag -width field_name
.It Fa gethook
is passed into the
.Fn arg_get
function at each invocation.
This enables the
.Fn arg_get
function to keep some state in between calls without using global or static
variables.
.It Fa field_name
is the field name supplied in
.Fa fmt ,
if any.
.El
.Pp
.Fn csio_decode
is used to decode information from the data in phase of the SCSI
transfer.
.Pp
The decoding is similar to
the command specifier processing of
.Fn csio_build
except that the data is extracted from the data pointed to by
.Fa csio->data_ptr .
The stdarg list should be pointers to integers instead of integer
values.
A seek field type and a suppression modifier are added.
The
.Fa *
suppression modifier (e.g.,
.Fa *i3
or
.Fa *b4 )
suppresses assignment from the field and can be used to skip
over bytes or bits in the data, without having to copy
them to a dummy variable in the arg list.
.Pp
The seek field type
.Fa s
permits you to skip over data.
This seeks to an absolute position
.Pq Fa s3
or a relative position
.Pq Fa s+3
in the data, based on whether or not the presence of the '+' sign.
The seek value can be specified as
.Fa v
and the next integer value from the argument list will be
used as the seek value.
.Pp
.Fn csio_decode_visit
operates like
.Fn csio_decode
except that instead of placing the decoded contents of the buffer in
variadic arguments, the decoded buffer contents are returned to the user
via the
.Fn arg_put
function that is passed in.
The
.Fn arg_put
function takes several arguments:
.Bl -tag -width letter
.It Fa hook
The "hook" is a mechanism to allow the
.Fn arg_put
function to save state in between calls.
.It Fa letter
is the letter describing the format of the argument being passed into the
function.
.It Fa val
is a void pointer to the value being passed into the function.
.It Fa count
is the size of the value being passed into the
.Fn arg_put
function.
The argument format determines the unit of measure.
.It Fa name
This is a text description of the field, if one was provided in the
.Fa fmt .
.El
.Pp
.Fn buff_decode
decodes an arbitrary data buffer using the method
described above for
.Fn csio_decode .
.Pp
.Fn buff_decode_visit
decodes an arbitrary data buffer using the method described above for
.Fn csio_decode_visit .
.Pp
.Fn csio_encode
encodes the
.Fa data_ptr
portion (not the CDB!) of a
.Va ccb_scsiio
structure, using the method described above for
.Fn csio_build .
.Pp
.Fn csio_encode_visit
encodes the
.Fa data_ptr
portion (not the CDB!) of a
.Va ccb_scsiio
structure, using the method described above for
.Fn csio_build_visit .
.Pp
.Fn buff_encode_visit
encodes an arbitrary data pointer, using the method described
above for
.Fn csio_build_visit .
.Sh RETURN VALUES
.Fn csio_build ,
.Fn csio_build_visit ,
.Fn csio_encode ,
.Fn csio_encode_visit ,
and
.Fn buff_encode_visit
return the number of fields processed.
.Pp
.Fn csio_decode ,
.Fn csio_decode_visit ,
.Fn buff_decode ,
and
.Fn buff_decode_visit
return the number of assignments performed.
.Sh SEE ALSO
.Xr cam 3 ,
.Xr pass 4 ,
.Xr camcontrol 8
.Sh HISTORY
The CAM versions of these functions are based upon similar functions
implemented for the old
.Fx
.Tn SCSI
layer.
The encoding/decoding functions in the old
.Tn SCSI
code were written by
.An Peter Dufault Aq Mt dufault@hda.com .
.Pp
Many systems have comparable interfaces to permit a user to construct a
SCSI command in user space.
.Pp
The old
.Va scsireq
data structure was almost identical to the SGI /dev/scsi data structure.
If anyone knows the name of the authors it should go here;
Peter Dufault
first read about it in a 1989 Sun Expert magazine.
.Pp
The new CCB data structures are derived from the CAM-2 and CAM-3
specifications.
.Pp
.An Peter Dufault
implemented a clone of SGI's interface in
.Bx 386
that
led to the original
.Fx
.Tn SCSI
library and the related kernel ioctl.
If anyone needs that for compatibility, contact
.Mt dufault@hda.com .
.Sh AUTHORS
.An -nosplit
.An Kenneth Merry Aq Mt ken@FreeBSD.org
implemented the CAM versions of these encoding and decoding functions.
This current work is based upon earlier work by
.An Peter Dufault Aq Mt dufault@hda.com .
.Sh BUGS
There should probably be a function that encodes both the CDB and the data
buffer portions of a
.Tn SCSI
CCB.
I discovered this while implementing the arbitrary command execution
code in
.Xr camcontrol 8 ,
but I have not yet had time to implement such a function.
.Pp
Some of the CCB flag descriptions really do not belong here.
Rather they
belong in a generic CCB man page.
Since that man page has not yet been
written, the shorter descriptions here will have to suffice.