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authorAlan Stern <stern@rowland.harvard.edu>2008-12-15 12:43:41 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2009-01-07 10:00:11 -0800
commit25ff1c316f6a763f1eefe7f8984b2d8c03888432 (patch)
tree623759675a8e2db8cbcacc665d97d874e57ab4c5 /Documentation
parent9ebd9616648bc0e47e7f8e1898c919305f1e6347 (diff)
USB: storage: add last-sector hacks
This patch (as1189b) adds some hacks to usb-storage for dealing with the growing problems involving bad capacity values and last-sector accesses: A new flag, US_FL_CAPACITY_OK, is created to indicate that the device is known to report its capacity correctly. An unusual_devs entry for Linux's own File-backed Storage Gadget is added with this flag set, since g_file_storage always reports the correct capacity and since the capacity need not be even (it is determined by the size of the backing file). An entry in unusual_devs.h which has only the CAPACITY_OK flag set shouldn't prejudice libusual, since the device will work perfectly well with either usb-storage or ub. So a new macro, COMPLIANT_DEV, is added to let libusual know about these entries. When a last-sector access succeeds and the total number of sectors is odd (the unexpected case, in which guessing that the number is even might cause trouble), a WARN is triggered. The kerneloops.org project will collect these warnings, allowing us to add CAPACITY_OK flags for the devices in question before implementing the default-to-even heuristic. If users want to prevent the stack dump produced by the WARN, they can disable the hack by adding an unusual_devs entry for their device with the CAPACITY_OK flag. When a last-sector access fails three times in a row and neither the FIX_CAPACITY nor the CAPACITY_OK flag is set, we assume the last-sector bug is present. We replace the existing status and sense data with values that will cause the SCSI core to fail the access immediately rather than retry indefinitely. This should fix the difficulties people have been having with Nokia phones. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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