On Wed, 3 Sep 2014, Dale R. Worley wrote: > > From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > > > > On Fri, 29 Aug 2014, Matthew Dharm wrote: > > > Is there an 'easy' way to override the detected size of a storage > > > device from userspace? If we had that, someone could write a helper > > > application which looked for this particular fubar and try to Do The > > > Right Thing(tm), or at least offer the user some options. > > > > You mean, force a Media Change event and override the capacity reported > > by the hardware? I'm not aware of any API for doing that, although it > > probably wouldn't be too hard to add one. > > > > How would the user know what value to put in for the capacity? Unless > > the drive had been hooked up to a different computer and the user > > manually noted the correct capacity and typed it in, it would have to > > be guesswork. > > The value would most sanely be extracted from the partition table. > (After verifying that the partition table looks correct.) That seems > to be what Windows does, and it seems to work consistently enough for > Windows to trust that method. Or at least, it could take the disk > size to be the end of the last partition, which would at least make > all the partitions accessible. If there is a partition table. It might be worthwhile to try an ATA pass-through command as well. > As somebody else hinted at, the userspace program could check the USB > device against a list of device types known to have this problem. > > It could even verify that the SCSI-reported size matches the size > reported by the partition table (modulo two-to-the-whatever) (at least > for GPT tables, I don't know if MBR tables report the disk size). They don't. Just the start and end of each partition. > Do we have any way of knowing what algorithm Windows uses in this > situation? Ask Microsoft. I suspect you're not likely to get an answer, though. Anyway, I can try writing a patch to add this capability. We'll see if it can solve your problem. 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
