1/* 	pg.h (c) 1998  Grant R. Guenther <grant@torque.net>
2 		       Under the terms of the GNU General Public License
3
4
5	pg.h defines the user interface to the generic ATAPI packet
6        command driver for parallel port ATAPI devices (pg). The
7	driver is loosely modelled after the generic SCSI driver, sg,
8	although the actual interface is different.
9
10	The pg driver provides a simple character device interface for
11        sending ATAPI commands to a device.  With the exception of the
12	ATAPI reset operation, all operations are performed by a pair
13        of read and write operations to the appropriate /dev/pgN device.
14	A write operation delivers a command and any outbound data in
15        a single buffer.  Normally, the write will succeed unless the
16        device is offline or malfunctioning, or there is already another
17	command pending.  If the write succeeds, it should be followed
18        immediately by a read operation, to obtain any returned data and
19        status information.  A read will fail if there is no operation
20        in progress.
21
22	As a special case, the device can be reset with a write operation,
23        and in this case, no following read is expected, or permitted.
24
25	There are no ioctl() operations.  Any single operation
26	may transfer at most PG_MAX_DATA bytes.  Note that the driver must
27        copy the data through an internal buffer.  In keeping with all
28	current ATAPI devices, command packets are assumed to be exactly
29	12 bytes in length.
30
31	To permit future changes to this interface, the headers in the
32	read and write buffers contain a single character "magic" flag.
33        Currently this flag must be the character "P".
34
35*/
36
37#define PG_MAGIC	'P'
38#define PG_RESET	'Z'
39#define PG_COMMAND	'C'
40
41#define PG_MAX_DATA	32768
42
43struct pg_write_hdr {
44
45	char	magic;		/* == PG_MAGIC */
46	char	func;		/* PG_RESET or PG_COMMAND */
47	int     dlen;		/* number of bytes expected to transfer */
48	int     timeout;	/* number of seconds before timeout */
49	char	packet[12];	/* packet command */
50
51};
52
53struct pg_read_hdr {
54
55	char	magic;		/* == PG_MAGIC */
56	char	scsi;		/* "scsi" status == sense key */
57	int	dlen;		/* size of device transfer request */
58	int     duration;	/* time in seconds command took */
59	char    pad[12];	/* not used */
60
61};
62
63/* end of pg.h */
64