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64 lines
2.2 KiB
C
64 lines
2.2 KiB
C
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/* pg.h (c) 1998 Grant R. Guenther <grant@torque.net>
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Under the terms of the GNU General Public License
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pg.h defines the user interface to the generic ATAPI packet
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command driver for parallel port ATAPI devices (pg). The
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driver is loosely modelled after the generic SCSI driver, sg,
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although the actual interface is different.
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The pg driver provides a simple character device interface for
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sending ATAPI commands to a device. With the exception of the
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ATAPI reset operation, all operations are performed by a pair
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of read and write operations to the appropriate /dev/pgN device.
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A write operation delivers a command and any outbound data in
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a single buffer. Normally, the write will succeed unless the
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device is offline or malfunctioning, or there is already another
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command pending. If the write succeeds, it should be followed
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immediately by a read operation, to obtain any returned data and
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status information. A read will fail if there is no operation
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in progress.
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As a special case, the device can be reset with a write operation,
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and in this case, no following read is expected, or permitted.
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There are no ioctl() operations. Any single operation
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may transfer at most PG_MAX_DATA bytes. Note that the driver must
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copy the data through an internal buffer. In keeping with all
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current ATAPI devices, command packets are assumed to be exactly
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12 bytes in length.
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To permit future changes to this interface, the headers in the
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read and write buffers contain a single character "magic" flag.
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Currently this flag must be the character "P".
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*/
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#define PG_MAGIC 'P'
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#define PG_RESET 'Z'
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#define PG_COMMAND 'C'
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#define PG_MAX_DATA 32768
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struct pg_write_hdr {
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char magic; /* == PG_MAGIC */
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char func; /* PG_RESET or PG_COMMAND */
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int dlen; /* number of bytes expected to transfer */
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int timeout; /* number of seconds before timeout */
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char packet[12]; /* packet command */
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};
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struct pg_read_hdr {
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char magic; /* == PG_MAGIC */
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char scsi; /* "scsi" status == sense key */
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int dlen; /* size of device transfer request */
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int duration; /* time in seconds command took */
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char pad[12]; /* not used */
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};
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/* end of pg.h */
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