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e2be04c7 | 1 | /* SPDX-License-Identifier: GPL-1.0+ WITH Linux-syscall-note */ |
1da177e4 LT |
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 | #define PG_MAGIC 'P' | |
39 | #define PG_RESET 'Z' | |
40 | #define PG_COMMAND 'C' | |
41 | ||
42 | #define PG_MAX_DATA 32768 | |
43 | ||
44 | struct pg_write_hdr { | |
45 | ||
46 | char magic; /* == PG_MAGIC */ | |
47 | char func; /* PG_RESET or PG_COMMAND */ | |
48 | int dlen; /* number of bytes expected to transfer */ | |
49 | int timeout; /* number of seconds before timeout */ | |
50 | char packet[12]; /* packet command */ | |
51 | ||
52 | }; | |
53 | ||
54 | struct pg_read_hdr { | |
55 | ||
56 | char magic; /* == PG_MAGIC */ | |
57 | char scsi; /* "scsi" status == sense key */ | |
58 | int dlen; /* size of device transfer request */ | |
59 | int duration; /* time in seconds command took */ | |
60 | char pad[12]; /* not used */ | |
61 | ||
62 | }; | |
63 | ||
64 | /* end of pg.h */ |