Phison PS2251-61 mode 8 (public/secure) based flash drive under linux. Hidden partition (2.49g one) is invisible to the OS unless unlocked w/ password + scsi raw command.

PS2251-61_mode_8.txt

usb 8-2: new high-speed USB device number 97 using xhci_hcd
usb 8-2: New USB device found, idVendor=0951, idProduct=1642
usb 8-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 8-2: Product: USB 2.0         
usb 8-2: Manufacturer:         
usb 8-2: SerialNumber: 20140105135617000000109A
usb-storage 8-2:1.0: USB Mass Storage device detected
scsi103 : usb-storage 8-2:1.0
scsi 103:0:0:0: Direct-Access              USB 2.0          1.00 PQ: 0 ANSI: 4
sd 103:0:0:0: Attached scsi generic sg3 type 0
sd 103:0:0:0: [sdb] 8396800 512-byte logical blocks: (4.29 GB/4.00 GiB)
sd 103:0:0:0: [sdb] Write Protect is off
sd 103:0:0:0: [sdb] Mode Sense: 23 00 00 00
sd 103:0:0:0: [sdb] No Caching mode page present
sd 103:0:0:0: [sdb] Assuming drive cache: write through
sd 103:0:0:0: [sdb] No Caching mode page present
sd 103:0:0:0: [sdb] Assuming drive cache: write through
 sdb: sdb1
sd 103:0:0:0: [sdb] No Caching mode page present
sd 103:0:0:0: [sdb] Assuming drive cache: write through
sd 103:0:0:0: [sdb] Attached SCSI removable disk


< scsi unlock command run >

sdb: detected capacity change from 4299161600 to 0
sd 103:0:0:0: [sdb] 4870144 512-byte logical blocks: (2.49 GB/2.32 GiB)
sd 103:0:0:0: [sdb] No Caching mode page present
sd 103:0:0:0: [sdb] Assuming drive cache: write through
sd 103:0:0:0: [sdb] No Caching mode page present
sd 103:0:0:0: [sdb] Assuming drive cache: write through
 sdb: sdb1