linux-headers (unknown)
1 /* SPDX-License-Identifier: GPL-1.0+ WITH Linux-syscall-note */
2 /* pg.h (c) 1998 Grant R. Guenther <grant@torque.net>
3 Under the terms of the GNU General Public License
4
5
6 pg.h defines the user interface to the generic ATAPI packet
7 command driver for parallel port ATAPI devices (pg). The
8 driver is loosely modelled after the generic SCSI driver, sg,
9 although the actual interface is different.
10
11 The pg driver provides a simple character device interface for
12 sending ATAPI commands to a device. With the exception of the
13 ATAPI reset operation, all operations are performed by a pair
14 of read and write operations to the appropriate /dev/pgN device.
15 A write operation delivers a command and any outbound data in
16 a single buffer. Normally, the write will succeed unless the
17 device is offline or malfunctioning, or there is already another
18 command pending. If the write succeeds, it should be followed
19 immediately by a read operation, to obtain any returned data and
20 status information. A read will fail if there is no operation
21 in progress.
22
23 As a special case, the device can be reset with a write operation,
24 and in this case, no following read is expected, or permitted.
25
26 There are no ioctl() operations. Any single operation
27 may transfer at most PG_MAX_DATA bytes. Note that the driver must
28 copy the data through an internal buffer. In keeping with all
29 current ATAPI devices, command packets are assumed to be exactly
30 12 bytes in length.
31
32 To permit future changes to this interface, the headers in the
33 read and write buffers contain a single character "magic" flag.
34 Currently this flag must be the character "P".
35
36 */
37
38 #ifndef _LINUX_PG_H
39 #define _LINUX_PG_H
40
41 #define PG_MAGIC 'P'
42 #define PG_RESET 'Z'
43 #define PG_COMMAND 'C'
44
45 #define PG_MAX_DATA 32768
46
47 struct pg_write_hdr {
48
49 char magic; /* == PG_MAGIC */
50 char func; /* PG_RESET or PG_COMMAND */
51 int dlen; /* number of bytes expected to transfer */
52 int timeout; /* number of seconds before timeout */
53 char packet[12]; /* packet command */
54
55 };
56
57 struct pg_read_hdr {
58
59 char magic; /* == PG_MAGIC */
60 char scsi; /* "scsi" status == sense key */
61 int dlen; /* size of device transfer request */
62 int duration; /* time in seconds command took */
63 char pad[12]; /* not used */
64
65 };
66
67 #endif /* _LINUX_PG_H */
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