linux/include
Alan Stern 50c4e96411 scsi: don't store LUN bits in CDB[1] for USB mass-storage devices
The SCSI specification requires that the second Command Data Byte
should contain the LUN value in its high-order bits if the recipient
device reports SCSI level 2 or below.  Nevertheless, some USB
mass-storage devices use those bits for other purposes in
vendor-specific commands.  Currently Linux has no way to send such
commands, because the SCSI stack always overwrites the LUN bits.

Testing shows that Windows 7 and XP do not store the LUN bits in the
CDB when sending commands to a USB device.  This doesn't matter if the
device uses the Bulk-Only or UAS transports (which virtually all
modern USB mass-storage devices do), as these have a separate
mechanism for sending the LUN value.

Therefore this patch introduces a flag in the Scsi_Host structure to
inform the SCSI midlayer that a transport does not require the LUN
bits to be stored in the CDB, and it makes usb-storage set this flag
for all devices using the Bulk-Only transport.  (UAS is handled by a
separate driver, but it doesn't really matter because no SCSI-2 or
lower device is at all likely to use UAS.)

The patch also cleans up the code responsible for storing the LUN
value by adding a bitflag to the scsi_device structure.  The test for
whether to stick the LUN value in the CDB can be made when the device
is probed, and stored for future use rather than being made over and
over in the fast path.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Tiziano Bacocco <tiziano.bacocco@gmail.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2014-09-15 16:01:58 -07:00
..
acpi ACPI / scan: not cache _SUN value in struct acpi_device_pnp 2014-09-03 22:41:14 +02:00
asm-generic This is the bulk of GPIO changes for the v3.17 development 2014-08-08 18:00:35 -07:00
clocksource
crypto crypto: drbg - backport "fix maximum value checks on 32 bit systems" 2014-09-05 15:52:28 +08:00
drm drm/radeon: add additional SI pci ids 2014-08-22 10:47:59 -04:00
dt-bindings Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma 2014-08-11 07:14:01 -07:00
keys
kvm
linux vfs: avoid non-forwarding large load after small store in path lookup 2014-09-14 17:28:32 -07:00
math-emu
media
memory
misc
net Merge tag 'master-2014-09-04' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless 2014-09-07 16:11:10 -07:00
pcmcia
ras
rdma Merge branches 'core', 'cxgb4', 'ipoib', 'iser', 'iwcm', 'mad', 'misc', 'mlx4', 'mlx5', 'ocrdma' and 'srp' into for-next 2014-08-14 08:58:04 -07:00
rxrpc
scsi scsi: don't store LUN bits in CDB[1] for USB mass-storage devices 2014-09-15 16:01:58 -07:00
soc/tegra
sound ASoC: core: fix .info for SND_SOC_BYTES_TLV 2014-08-18 08:59:12 -05:00
target
trace net: treewide: Fix typo found in DocBook/networking.xml 2014-09-05 17:35:28 -07:00
uapi USB fixes for 3.17-rc5 2014-09-12 11:59:10 -07:00
video fbdev changes for 3.17 2014-08-08 18:09:33 -07:00
xen xen/arm: introduce XENFEAT_grant_map_identity 2014-09-11 18:11:52 +00:00
Kbuild