ntddscsi.h wraps SCSI_PASS_THROUGH_DIRECT in #pragma pack(push, 4),
forcing the PVOID DataBuffer field to 4-byte alignment even on 64-bit
hosts. The Rust struct used bare #[repr(C)], so the compiler applied
natural 8-byte pointer alignment and inserted 4 padding bytes after
TimeOutValue. That shifted DataBuffer to offset 24 (SDK: 20),
SenseInfoOffset to 32 (28), and Cdb to 36 (32), and grew the struct to
56 bytes (48). DeviceIoControl reads at the SDK offsets, so every SPTI
ioctl on 64-bit Windows either got rejected or interpreted garbage as
the CDB and DataBuffer pointer.
Add #[repr(C, packed(4))] to ScsiPassThroughDirect and the companion
SptwbDirect (so offset_of!(SptwbDirect, sense) stays correct for
SenseInfoOffset), plus a layout regression test asserting DataBuffer at
offset 20 and a 48-byte struct size.
Matthew Jackson
97ae47b3ea