On Tue, 8 May 2012, Norman Diamond wrote: > In my case there is no other way that a host (PC or other, any OS or > driver) could obtain a reported capacity past the 2.2TB mark. > Sometimes I guess a USB-to-[S]ATA bridge might obey ATA passthru of > an ATA Identify command though I haven't seen one. There definitely are some bridges which handle ATA passthru correctly. > >> I have a feeling we have to do both READ CAPACITY(10) and READ > >> CAPACITY(16), and if we see wraparound then we should either truncate > >> the drive to 2.2TB or avoid the drive entirely.� I think truncation > >> is safe enough at this point -- if a partition gets truncated then > >> subsequent attempts to mount will fail, so any existing but > >> inaccessible data will be safe from harm, while accessible data will > >> be read and written correctly. > > > > That sounds like the best approach.� You would want to do this for all > > USB drives?� Or only those known to be (S)ATA bridges? > > I think it's needed with [S]ATA bridges, whether or not we know that > they're bridges. I think it's probably not needed with anything > else, but it probably doesn't hurt to do it with anything else. > Therefore it's probably safest to do it with all USB drives. Except that READ CAPACITY(16) might cause some buggy devices to crash. I guess there wasn't much point in asking the question... Putting everything together, it looks like you're asking for three new flags: CAPACITY_10_AND_16: Issue both READ CAPACITY and READ CAPACITY(16), and if READ CAPACITY(16) gives a result > 2 TB and READ CAPACITY doesn't give 0xffffffff, truncate the size to 2 TB; CAPACITY_HEURISTICS_63: Don't decrement the capacity if the reported capacity is a multiple of 63, but otherwise behave like CAPACITY_HEURISTICS; TEST_CAPACITY: Try to do a single-block read of the last reported block. Right? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
