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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 */