cam(3)

NAME

cam_open_device, cam_open_spec_device, cam_open_btl,

cam_open_pass,
cam_close_device, cam_close_spec_device, cam_getccb,

cam_send_ccb,
cam_freeccb, cam_path_string, cam_device_dup,

cam_device_copy,
cam_get_device - CAM user library

LIBRARY

library ``libcam''

SYNOPSIS

#include <stdio.h>
#include <camlib.h>
struct cam_device *
cam_open_device(const char *path, int flags);
struct cam_device *
cam_open_spec_device(const  char  *dev_name,  int  unit, int
flags,
        struct cam_device *device);
struct cam_device *
cam_open_btl(path_id_t path_id, target_id_t target_id,
        lun_id_t target_lun, int  flags,  struct  cam_device
*device);
struct cam_device *
cam_open_pass(const char *path, int flags, struct cam_device
*device);
void
cam_close_device(struct cam_device *dev);
void
cam_close_spec_device(struct cam_device *dev);
union ccb *
cam_getccb(struct cam_device *dev);
int
cam_send_ccb(struct cam_device *device, union ccb *ccb);
void
cam_freeccb(union ccb *ccb);
char *
cam_path_string(struct cam_device *dev, char *str, int len);
struct cam_device *
cam_device_dup(struct cam_device *device);
void
cam_device_copy(struct  cam_device  *src,  struct cam_device
*dst);
int
cam_get_device(const  char  *path,   char   *dev_name,   int
devnamelen,
        int *unit);

DESCRIPTION

The CAM library consists of a number of functions designed

to aid in programming with the CAM subsystem. This man page covers the

basic set of
library functions. More functions are documented in the man

pages listed
below.

Many of the CAM library functions use the cam_device struc

ture:

struct cam_device {

char device_path[MAXPATHLEN+1];/*

* Path

name of the
* device

given by the
* user.

This may be
* null if

the user
* states

the device
* name

and unit number
* sepa

rately.
*/

char given_dev_name[DEV_IDLEN+1];/*

* De

vice name given by
* the

user.
*/

u_int32_t given_unit_number; /*

* Unit

number given by
* the

user.
*/

char device_name[DEV_IDLEN+1];/*

* Name of

the device,
* e.g.
*/

u_int32_t dev_unit_num; /* Unit number of

the passthrough

* device associated

with this
* particular de

vice.
*/

char sim_name[SIM_IDLEN+1];/*

* Controller

name, e.g.'ahc'
*/

u_int32_t sim_unit_number; /* Controller unit

number */
u_int32_t bus_id; /* Controller bus

number */
lun_id_t target_lun; /* Logical Unit

Number */
target_id_t target_id; /* Target ID */
path_id_t path_id; /* System SCSI bus

number */
u_int16_t pd_type; /* type of periph

eral device */
struct scsi_inquiry_data inq_data; /* SCSI Inquiry

data */
u_int8_t serial_num[252]; /* device serial

number */
u_int8_t serial_num_len; /* length of the

serial number */
u_int8_t sync_period; /* Negotiated sync

period */
u_int8_t sync_offset; /* Negotiated sync

offset */
u_int8_t bus_width; /* Negotiated bus

width */
int fd; /* file descriptor

for device */

};

cam_open_device() takes as arguments a string describing the

device it is
to open, and flags suitable for passing to open(2). The

"path" passed in
may actually be most any type of string that contains a de

vice name and
unit number to be opened. The string will be parsed by

cam_get_device()
into a device name and unit number. Once the device name

and unit number
are determined, a lookup is performed to determine the

passthrough device
that corresponds to the given device. cam_open_device() is

rather simple
to use, but it is not really suitable for general use be

cause its behavior is not necessarily deterministic. Programmers writing

new applications should make the extra effort to use one of the other

open routines
documented below.

cam_open_spec_device() opens the pass(4) device that corre

sponds to the
device name and unit number passed in. The flags should be

flags suitable for passing to open(2). The device argument is option

al. The user
may supply pre-allocated space for the cam_device structure.

If the
device argument is NULL, cam_open_spec_device() will allo

cate space for
the cam_device structure using malloc(3).

cam_open_btl() is similar to cam_open_spec_device(), except

that it takes
a SCSI bus, target and logical unit instead of a device name

and unit
number as arguments. The path_id argument is the CAM equiv

alent of a
SCSI bus number. It represents the logical bus number in

the system.
The flags should be flags suitable for passing to open(2).

As with
cam_open_spec_device(), the device argument is optional.

cam_open_pass() takes as an argument the path of a pass(4)

device to
open. No translation or lookup is performed, so the path

passed in must
be that of a CAM pass(4) device. The flags should be flags

suitable for
passing to open(2). The device argument, as with

cam_open_spec_device()
and cam_open_btl(), should be NULL if the user wants the CAM

library to
allocate space for the cam_device structure.

cam_close_device() frees
the cam_device structure allocated by one of the above

open() calls, and
closes the file descriptor to the passthrough device. This

routine
should not be called if the user allocated space for the

cam_device
structure. Instead, the user should call

cam_close_spec_device().

cam_close_spec_device() merely closes the file descriptor

opened in one
of the open() routines described above. This function

should be called
when the cam_device structure was allocated by the caller,

rather than
the CAM library.

cam_getccb() allocates a CCB using malloc(3) and sets fields

in the CCB
header using values from the cam_device structure.

cam_send_ccb() sends the given ccb to the device described

in the
cam_device structure.

cam_freeccb() frees CCBs allocated by cam_getccb().

cam_path_string() takes as arguments a cam_device structure,

and a string
with length len. It creates a colon-terminated printing

prefix string
similar to the ones used by the kernel. e.g.:

"(cd0:ahc1:0:4:0): ".
cam_path_string() will place at most len-1 characters into

str. The
len'th character will be the terminating ` '.

cam_device_dup() operates in a fashion similar to strdup(3).

It allocates space for a cam_device structure and copies the con

tents of the
passed-in device structure to the newly allocated structure.

cam_device_copy() copies the src structure to dst.

cam_get_device() takes a path argument containing a string

with a device
name followed by a unit number. It then breaks the string

down into a
device name and unit number, and passes them back in

dev_name and unit,
respectively. cam_get_device() can handle strings of the

following
forms, at least:

/dev/foo0a
/dev/foo1s2c
foo0
foo0a
nfoo0

cam_get_device() is provided as a convenience function for

applications
that need to provide functionality similar to

cam_open_device(). Programmers are encouraged to use more deterministic methods of

obtaining
device names and unit numbers if possible.

RETURN VALUES

cam_open_device(), cam_open_spec_device(), cam_open_btl(),

and
cam_open_pass() return a pointer to a cam_device structure,

or NULL if
there was an error.

cam_getccb() returns an allocated and partially initialized

CCB, or NULL
if allocation of the CCB failed.

cam_send_ccb() returns a value of -1 if an error occured,

and errno is
set to indicate the error.

cam_path_string() returns a filled printing prefix string as

a convenience. This is the same str that is passed into

cam_path_string().

cam_device_dup() returns a copy of the device passed in, or

NULL if an
error occurred.

cam_get_device() returns 0 for success, and -1 to indicate

failure.

If an error is returned from one of the base CAM library

functions
described here, the reason for the error is generally print

ed in the
global string cam_errbuf which is CAM_ERRBUF_SIZE characters

long.

SEE ALSO

cam_cdbparse(3), pass(4), camcontrol(8)

HISTORY

The CAM library first appeared in FreeBSD 3.0.

AUTHORS

Kenneth Merry <ken@FreeBSD.org>

BUGS

cam_open_device() does not check to see if the path passed

in is a symlink to something. It also does not check to see if the

path passed in
is an actual pass(4) device. The former would be rather

easy to implement, but the latter would require a definitive way to iden

tify a device
node as a pass(4) device.

Some of the functions are possibly mis-named or poorly

named.

BSD October 10, 1998

BSD