On Fri, Nov 12, 2021 at 07:21:34PM +0100, DocMAX wrote: > The first and more buggy maybe. > So you are not going to fix this just blacklist uas by default? I don't understand what you mean. How could I fix a broken device? If the device is unable to work with uas but _is_ able to work with usb-storage, then disabling uas for it seems like the only possible way to proceed. > I was so happy that i got a uas capable device and now the joy is over... > :-( Do you know whether the device works with the UAS protocol under Windows? If you want more detailed information about exactly what is happening in the communication between the computer and the device, you can collect a usbmon trace. Or you can record the information going over the bus using Wireshark (which I think will also work on Windows). > Is there detailed information of the uas/usb-storage differences? (Very > detailed, not just "it's faster") I'm not aware of any such discussions, although ones probably exist somewhere. The individual protocols are well described in documents hosted on the usb.org web site, but as far as I know none of them talk about the differences between the two protocols. A quick summary of the major aspects would look like this: The commands and status responses are bundled into packets in slightly different ways (different packet headers and so on), but this difference is relatively small. uas uses USB streams, a feature of USB-3 not present in USB-2, to issue multiple commands (and their associated data) in parallel, allowing the device to process them in any order it wants. usb-storage, by contrast, sends only one command at a time and waits for it to complete before sending the next command. That's the major difference between the protocols, and it is what accounts for the difference in speed. uas includes means for the computer to query the device about the state of ongoing commands, which is not possible with usb-storage. Alan Stern
