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CAM (3) | C library functions | Unix Manual Pages | :man


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


Return Values
See Also


.Lb libcam


.In stdio.h
.In camlib.h struct cam_device *
.Fo cam_open_device "const char *path" "int flags"
.Fc struct cam_device *
.Fo cam_open_spec_device "const char *dev_name" "int unit" "int flags" "struct cam_device *device"
.Fc struct cam_device *
.Fo cam_open_btl "path_id_t path_id" "target_id_t target_id" "lun_id_t target_lun" "int flags" "struct cam_device *device"
.Fc struct cam_device *
.Fo cam_open_pass "const char *path" "int flags" "struct cam_device *device"
.Fc void
.Fo cam_close_device "struct cam_device *dev"
.Fc void
.Fo cam_close_spec_device "struct cam_device *dev"
.Fc union ccb *
.Fo cam_getccb "struct cam_device *dev"
.Fc int
.Fo cam_send_ccb "struct cam_device *device" "union ccb *ccb"
.Fc void
.Fo cam_freeccb "union ccb *ccb"
.Fc char *
.Fo cam_path_string "struct cam_device *dev" "char *str" "int len"
.Fc struct cam_device *
.Fo cam_device_dup "struct cam_device *device"
.Fc void
.Fo cam_device_copy "struct cam_device *src" "struct cam_device *dst"
.Fc int
.Fo cam_get_device "const char *path" "char *dev_name" "int devnamelen" "int *unit"


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 structure:
struct cam_device {
char device_path[MAXPATHLEN+1];/*
* Pathname of the
* device given by the
* user. This may be
* null if the user
* states the device
* name and unit number
* separately.
char given_dev_name[DEV_IDLEN+1];/*
* Device 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. ’pass’
u_int32_t dev_unit_num; /* Unit number of the passthrough
* device associated with this
* particular device.

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_ttarget_id; /* Target ID */
path_id_t path_id; /* System SCSI bus number */
u_int16_t pd_type; /* type of peripheral 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 device 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 because 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 corresponds to the device name and unit number passed in. The flags should be flags suitable for passing to open(2). The device argument is optional. The user may supply pre-allocated space for the cam_device structure. If the device argument is NULL, cam_open_spec_device will allocate 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 equivalent 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 ‘\0’.

cam_device_dup operates in a fashion similar to strdup(3). It allocates space for a cam_device structure and copies the contents 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:


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.


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 printed in the global string cam_errbuf which is CAM_ERRBUF_SIZE characters long.


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




pass(4) pass(4)

Created by Blin Media, 2008-2013