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![Alan Stern](/assets/img/avatar_default.png)
Ever since commit a621bac3044e ("scsi_lib: correctly retry failed zero length REQ_TYPE_FS commands"), people have been getting bogus error messages for USB disk drives using ATA pass-thru. For example: [ 1344.880193] sd 6:0:0:0: [sdb] Attached SCSI disk [ 1345.069152] sd 6:0:0:0: [sdb] tag#0 FAILED Result: hostbyte=DID_ERROR driverbyte=DRIVER_SENSE [ 1345.069159] sd 6:0:0:0: [sdb] tag#0 Sense Key : Hardware Error [current] [descriptor] [ 1345.069162] sd 6:0:0:0: [sdb] tag#0 Add. Sense: No additional sense information [ 1345.069168] sd 6:0:0:0: [sdb] tag#0 CDB: ATA command pass through(16) 85 06 20 00 00 00 00 00 00 00 00 00 00 00 e5 00 [ 1345.172252] sd 6:0:0:0: [sdb] tag#0 FAILED Result: hostbyte=DID_ERROR driverbyte=DRIVER_SENSE [ 1345.172258] sd 6:0:0:0: [sdb] tag#0 Sense Key : Hardware Error [current] [descriptor] [ 1345.172261] sd 6:0:0:0: [sdb] tag#0 Add. Sense: No additional sense information [ 1345.172266] sd 6:0:0:0: [sdb] tag#0 CDB: ATA command pass through(12)/Blank a1 06 20 da 00 00 4f c2 00 b0 00 00 These messages can be quite annoying, because programs like udisks2 provoke them every 10 minutes or so. Other programs can also have this effect, such as those in smartmontools. I don't fully understand how that commit induced the SCSI core to log these error messages, but the underlying cause for them is code added to usb-storage by commit f1a0743bc0e7 ("USB: storage: When a device returns no sense data, call it a Hardware Error"). At the time it was necessary to do this, in order to prevent an infinite retry loop with some not-so-great mass storage devices. However, the ATA pass-thru protocol uses SCSI sense data to return command status values, and some devices always report Check Condition status for ATA pass-thru commands to ensure that the host retrieves the sense data, even if the command succeeded. This violates the USB mass-storage protocol (Check Condition status is supposed to mean the command failed), but we can't help that. This patch attempts to mitigate the problem of these bogus error reports by changing usb-storage. The HARDWARE ERROR sense key will be inserted only for commands that aren't ATA pass-thru. Thanks to Ewan Milne for pointing out that this mechanism was present in usb-storage. 8 years after writing it, I had completely forgotten its existence. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Tested-by: Kris Lindgren <kris.lindgren@gmail.com> Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1351305 CC: Ewan D. Milne <emilne@redhat.com> CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources: * This source code. This is necessarily an evolving work, and includes kerneldoc that should help you get a current overview. ("make pdfdocs", and then look at "usb.pdf" for host side and "gadget.pdf" for peripheral side.) Also, Documentation/usb has more information. * The USB 2.0 specification (from www.usb.org), with supplements such as those for USB OTG and the various device classes. The USB specification has a good overview chapter, and USB peripherals conform to the widely known "Chapter 9". * Chip specifications for USB controllers. Examples include host controllers (on PCs, servers, and more); peripheral controllers (in devices with Linux firmware, like printers or cell phones); and hard-wired peripherals like Ethernet adapters. * Specifications for other protocols implemented by USB peripheral functions. Some are vendor-specific; others are vendor-neutral but just standardized outside of the www.usb.org team. Here is a list of what each subdirectory here is, and what is contained in them. core/ - This is for the core USB host code, including the usbfs files and the hub class driver ("hub_wq"). host/ - This is for USB host controller drivers. This includes UHCI, OHCI, EHCI, and others that might be used with more specialized "embedded" systems. gadget/ - This is for USB peripheral controller drivers and the various gadget drivers which talk to them. Individual USB driver directories. A new driver should be added to the first subdirectory in the list below that it fits into. image/ - This is for still image drivers, like scanners or digital cameras. ../input/ - This is for any driver that uses the input subsystem, like keyboard, mice, touchscreens, tablets, etc. ../media/ - This is for multimedia drivers, like video cameras, radios, and any other drivers that talk to the v4l subsystem. ../net/ - This is for network drivers. serial/ - This is for USB to serial drivers. storage/ - This is for USB mass-storage drivers. class/ - This is for all USB device drivers that do not fit into any of the above categories, and work for a range of USB Class specified devices. misc/ - This is for all USB device drivers that do not fit into any of the above categories.