freebsd-dev/lib/libcam/cam.3

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.Dd October 10, 1998
.Os FreeBSD
.Dt CAM 3
.Sh NAME
.Nm cam_open_device ,
.Nm cam_open_spec_device ,
.Nm cam_open_btl ,
.Nm cam_open_pass ,
.Nm cam_close_device ,
.Nm cam_close_spec_device ,
.Nm cam_getccb ,
.Nm cam_send_ccb ,
.Nm cam_freeccb ,
.Nm cam_path_string ,
.Nm cam_device_dup ,
.Nm cam_device_copy ,
.Nm cam_get_device
.Nd CAM user library
.Sh LIBRARY
.Lb libcam
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Fd #include <camlib.h>
.Ft struct cam_device *
.Fo cam_open_device
.Fa "const char *path"
.Fa "int flags"
.Fc
.Ft struct cam_device *
.Fo cam_open_spec_device
.Fa "const char *dev_name"
.Fa "int unit"
.Fa "int flags"
.Fa "struct cam_device *device"
.Fc
.Ft struct cam_device *
.Fo cam_open_btl
.Fa "path_id_t path_id"
.Fa "target_id_t target_id"
.Fa "lun_id_t target_lun"
.Fa "int flags"
.Fa "struct cam_device *device"
.Fc
.Ft struct cam_device *
.Fo cam_open_pass
.Fa "const char *path"
.Fa "int flags"
.Fa "struct cam_device *device"
.Fc
.Ft void
.Fo cam_close_device
.Fa "struct cam_device *dev"
.Fc
.Ft void
.Fo cam_close_spec_device
.Fa "struct cam_device *dev"
.Fc
.Ft union ccb *
.Fo cam_getccb
.Fa "struct cam_device *dev"
.Fc
.Ft int
.Fo cam_send_ccb
.Fa "struct cam_device *device"
.Fa "union ccb *ccb"
.Fc
.Ft void
.Fo cam_freeccb
.Fa "union ccb *ccb"
.Fc
.Ft char *
.Fo cam_path_string
.Fa "struct cam_device *dev"
.Fa "char *str"
.Fa "int len"
.Fc
.Ft struct cam_device *
.Fo cam_device_dup
.Fa "struct cam_device *device"
.Fc
.Ft void
.Fo cam_device_copy
.Fa "struct cam_device *src"
.Fa "struct cam_device *dst"
.Fc
.Ft int
.Fo cam_get_device
.Fa "const char *path"
.Fa "char *dev_name"
.Fa "int devnamelen"
.Fa "int *unit"
.Fc
.Sh 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.
.Pp
Many of the CAM library functions use the
.Va cam_device
structure:
.Bd -literal
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_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 */
};
.Ed
.Pp
.Fn cam_open_device
takes as arguments a string describing the device it is to open, and
.Ar flags
suitable for passing to
.Xr 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
.Fn 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.
.Fn 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.
.Pp
.Fn cam_open_spec_device
opens the
.Xr pass 4
device that corresponds to the device name and unit number passed in.  The
.Ar flags
should be flags suitable for passing to
.Xr open 2 .
The
.Ar device
argument is optional.  The user may supply pre-allocated space for the
.Va cam_device
structure.  If the
.Ar device
argument is
.Va NULL ,
.Fn cam_open_spec_device
will allocate space for the
.Va cam_device
structure using
.Xr malloc 3 .
.Pp
.Fn cam_open_btl
is similar to
.Fn cam_open_spec_device ,
except that it takes a
.Tn SCSI
bus, target and logical unit instead of a device name and unit number as
arguments.  The
.Va path_id
argument is the CAM equivalent of a
.Tn SCSI
bus number.  It represents the logical bus number in the system.  The
.Ar flags
should be flags suitable for passing to
.Xr open 2 .
As with
.Fn cam_open_spec_device ,
the
.Fa device
argument is optional.
.Pp
.Fn cam_open_pass
takes as an argument the
.Fa path
of a
.Xr pass 4
device to open.  No translation or lookup is performed, so the path passed
in must be that of a CAM
.Xr pass 4
device.  The
.Fa flags
should be flags suitable for passing to
.Xr open 2 .
The
.Fa device
argument, as with
.Fn cam_open_spec_device
and
.Fn cam_open_btl ,
should be NULL if the user wants the CAM library to allocate space for the
.Va cam_device
structure.
.Fn cam_close_device
frees the
.Va 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
.Va cam_device
structure.  Instead, the user should call
.Fn cam_close_spec_device .
.Pp
.Fn 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
.Va cam_device
structure was allocated by the caller, rather than the CAM library.
.Pp
.Fn cam_getccb
allocates a CCB
using
.Xr malloc 3
and sets fields in the CCB header using values from the
.Va cam_device
structure.
.Pp
.Fn cam_send_ccb
sends the given
.Va ccb
to the
.Fa device
described in the
.Va cam_device
structure.
.Pp
.Fn cam_freeccb
frees CCBs allocated by
.Fn cam_getccb .
.Pp
.Fn cam_path_string
takes as arguments a
.Va cam_device
structure, and a string with length
.Fa len .
It creates a colon-terminated printing prefix string similar to the ones
used by the kernel.  e.g.:  "(cd0:ahc1:0:4:0): ".
.Fn cam_path_string
will place at most
.Fa len Ns \-1
characters into
.Ar str .
The
.Ar len Ns 'th
character will be the terminating
.Ql \e0 .
.Pp
.Fn cam_device_dup
operates in a fashion similar to
.Xr strdup 3 .
It allocates space for a
.Va cam_device
structure and copies the contents of the passed-in
.Fa device
structure to the newly allocated structure.
.Pp
.Fn cam_device_copy
copies the
.Fa src
structure to
.Fa dst .
.Pp
.Fn cam_get_device
takes a
.Fa 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
.Fa dev_name
and
.Fa unit ,
respectively.
.Fn cam_get_device
can handle strings of the following forms, at least:
.Pp
.Bl -tag -width 1234 -compact
.It /dev/foo0a
.It /dev/foo1s2c
.It foo0
.It foo0a
.It nfoo0
.El
.Pp
.Fn cam_get_device
is provided as a convenience function for applications that need to provide
functionality similar to
.Fn cam_open_device .
Programmers are encouraged to use more deterministic methods of obtaining
device names and unit numbers if possible.
.Sh RETURN VALUES
.Fn cam_open_device ,
.Fn cam_open_spec_device ,
.Fn cam_open_btl ,
and
.Fn cam_open_pass
return a pointer to a
.Va cam_device
structure, or NULL if there was an error.
.Pp
.Fn cam_getccb
returns an allocated and partially initialized CCB, or NULL if allocation
of the CCB failed.
.Pp
.Fn cam_send_ccb
returns a value of -1 if an error occured, and 
.Va errno
is set to indicate the error.
.Pp
.Fn cam_path_string
returns a filled printing prefix string as a convenience.  This is the same
.Fa str
that is passed into
.Fn cam_path_string .
.Pp
.Fn cam_device_dup
returns a copy of the
.Va device
passed in, or NULL if an error occurred.
.Pp
.Fn cam_get_device
returns 0 for success, and -1 to indicate failure.
.Pp
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
.Va cam_errbuf
which is
.Dv CAM_ERRBUF_SIZE
characters long.
.Sh SEE ALSO
.Xr cam_cdbparse 3 ,
.Xr pass 4 ,
.Xr camcontrol 8
.Sh HISTORY
The CAM library first appeared in 
.Fx 3.0 .
.Sh AUTHORS
.An Kenneth Merry Aq ken@FreeBSD.org
.Sh BUGS
.Fn cam_open_device
doesn't check to see if the
.Fa path
passed in is a symlink to something.  It also doesn't check to see if the
.Fa path
passed in is an actual
.Xr pass 4
device.  The former would be rather easy to implement, but the latter would
require a definitive way to identify a device node as a
.Xr pass 4
device.
.Pp
Some of the functions are possibly mis-named or poorly named.