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DESCRIPTION

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.'ahci'
					       */
	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 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 isn't really suitable for general use because its behavior isn't 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:

/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.