On Thu, 3 May 2012, Norman Diamond wrote: > >> Meanwhile I tested my Prolific bridge again too, with an additional > >> PATA-to-SATA adapter.� Windows sees 3TB but Linux sees 800GB minus > >> one block.� Do you need usbmon for that? > > > > Probably the two bridges have the same bug. > > I agree, "Probably". If you want to find out for certain, collect a usbmon trace with the Prolific bridge. > > It looks like the bridge is sending just the least-significant 32 bits > > of the capacity.� What it should have done is reply with 0xffffffff.� > > Then the kernel would know to try again with a READ CAPACITY(16) > > command, which is capable of retrieving values larger than 32 bits. > > You are right, bridges' failures to reply with 0xffffffff are > bridges' bugs. Obviously Windows proceeded to try a READ > CAPACITY(16) regardless. Don't be so sure. I have seen reports from others indicating quite clearly that Windows would believe a partition table even when it contradicted a device's reported capacity. For example, early card readers can handle SD cards but not SDHC. When an SDHC card is inserted in such a reader, the reported capacity is too small. Windows would nevertheless believe the partition information. Interestingly, when the user would try to repartition the card, Windows would not allow a new partition to exceed the reported capacity. There are equivalents of usbmon available for various versions of Windows. You could try using one of them to see what commands your Windows sends. > I hope old bridges that can't handle READ > CAPACITY(16) at least avoid crashing when presented with that > command, so a workaround could always send that command. Or a quirk > could be added to say which bridges crash. If a bridge sends an > ordinary rejection saying that it can't handle the command but > doesn't crash, then there's no need to avoid the attempt. You can try sending the command yourself using sg_raw, to see how well your bridges handle it. 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
