SG_SET_FORCE_PACK_ID 0x227b. Assumes 3rd argument is pointing to an int. 0 (default) instructs read()
to return the oldest (written) packet if multiple packets are
waiting to be read. 1 instructs read() to view the sg_io_hdr::pack_id
(or sg_header::pack_id) as input and return the oldest packet matching
that pack_id or wait until it arrives. If the file descriptor is in
O_NONBLOCK state, rather than wait this ioctl() will yield EAGAIN.
As a special case the pack_id of -1
given to read() in the mode will match the oldest packet.
Only the current file descriptor is affected by this command.
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