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