block/swim: Check drive type

The SWIM chip is compatible with GCR-mode Sony 400K/800K drives but
this driver only supports MFM mode. Therefore only Sony FDHD drives
are supported. Skip incompatible drives.

Cc: Laurent Vivier <lvivier@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: stable@vger.kernel.org # v4.14+
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Acked-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/swim.c

@@ -829,10 +829,12 @@ static int swim_floppy_init(struct swim_priv *swd)
 	/* scan floppy drives */
 
 	swim_drive(base, INTERNAL_DRIVE);
-	if (swim_readbit(base, DRIVE_PRESENT))
+	if (swim_readbit(base, DRIVE_PRESENT) &&
+	    !swim_readbit(base, ONEMEG_DRIVE))
 		swim_add_floppy(swd, INTERNAL_DRIVE);
 	swim_drive(base, EXTERNAL_DRIVE);
-	if (swim_readbit(base, DRIVE_PRESENT))
+	if (swim_readbit(base, DRIVE_PRESENT) &&
+	    !swim_readbit(base, ONEMEG_DRIVE))
 		swim_add_floppy(swd, EXTERNAL_DRIVE);
 
 	/* register floppy drives */