• Alan Stern's avatar
    USB: storage: add last-sector hacks · 25ff1c31
    Alan Stern authored
    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: default avatarAlan Stern <stern@rowland.harvard.edu>
    Cc: stable <stable@kernel.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    25ff1c31
libusual.c 6.6 KB