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| Rev | Author | Line No. | Line |
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| 422 | giacomo | 1 | /* pg.h (c) 1998 Grant R. Guenther <grant@torque.net> |
| 2 | Under the terms of the GNU General Public License |
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| 3 | |||
| 4 | |||
| 5 | pg.h defines the user interface to the generic ATAPI packet |
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| 6 | command driver for parallel port ATAPI devices (pg). The |
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| 7 | driver is loosely modelled after the generic SCSI driver, sg, |
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| 8 | although the actual interface is different. |
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| 9 | |||
| 10 | The pg driver provides a simple character device interface for |
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| 11 | sending ATAPI commands to a device. With the exception of the |
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| 12 | ATAPI reset operation, all operations are performed by a pair |
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| 13 | of read and write operations to the appropriate /dev/pgN device. |
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| 14 | A write operation delivers a command and any outbound data in |
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| 15 | a single buffer. Normally, the write will succeed unless the |
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| 16 | device is offline or malfunctioning, or there is already another |
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| 17 | command pending. If the write succeeds, it should be followed |
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| 18 | immediately by a read operation, to obtain any returned data and |
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| 19 | status information. A read will fail if there is no operation |
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| 20 | in progress. |
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| 21 | |||
| 22 | As a special case, the device can be reset with a write operation, |
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| 23 | and in this case, no following read is expected, or permitted. |
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| 24 | |||
| 25 | There are no ioctl() operations. Any single operation |
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| 26 | may transfer at most PG_MAX_DATA bytes. Note that the driver must |
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| 27 | copy the data through an internal buffer. In keeping with all |
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| 28 | current ATAPI devices, command packets are assumed to be exactly |
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| 29 | 12 bytes in length. |
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| 30 | |||
| 31 | To permit future changes to this interface, the headers in the |
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| 32 | read and write buffers contain a single character "magic" flag. |
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| 33 | Currently this flag must be the character "P". |
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| 34 | |||
| 35 | */ |
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| 36 | |||
| 37 | #define PG_MAGIC 'P' |
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| 38 | #define PG_RESET 'Z' |
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| 39 | #define PG_COMMAND 'C' |
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| 40 | |||
| 41 | #define PG_MAX_DATA 32768 |
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| 42 | |||
| 43 | struct pg_write_hdr { |
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| 44 | |||
| 45 | char magic; /* == PG_MAGIC */ |
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| 46 | char func; /* PG_RESET or PG_COMMAND */ |
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| 47 | int dlen; /* number of bytes expected to transfer */ |
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| 48 | int timeout; /* number of seconds before timeout */ |
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| 49 | char packet[12]; /* packet command */ |
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| 50 | |||
| 51 | }; |
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| 52 | |||
| 53 | struct pg_read_hdr { |
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| 54 | |||
| 55 | char magic; /* == PG_MAGIC */ |
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| 56 | char scsi; /* "scsi" status == sense key */ |
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| 57 | int dlen; /* size of device transfer request */ |
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| 58 | int duration; /* time in seconds command took */ |
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| 59 | char pad[12]; /* not used */ |
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| 60 | |||
| 61 | }; |
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| 62 | |||
| 63 | /* end of pg.h */ |