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    SubjectRe: [PATCH] usb: also announce bcdDevice
    On Sat, 5 May 2012, Martin Mokrejs wrote:

    > Greg Kroah-Hartman wrote:
    > > On Sat, May 05, 2012 at 02:14:43PM +0200, Martin Mokrejs wrote:
    > >> Paul Bolle wrote:
    > >>> Currently announce_device() does print the idVendor and idProduct values
    > >>> but does not print the bcdDevice value. USB devices are accurately
    > >>> identified by all three values. See, for instance, the USB storage
    > >>> quirks which will only apply for a certain (range of) bcdDevice
    > >>> value(s). So it seems useful to also print bcdDevice when announcing USB
    > >>> devices.
    > >>
    > >> Could it also report negotiated speed? full-speed, high-speed, super-speed?
    > >
    > > All of this, including the bcdDevice, can be found in sysfs. So I don't
    > > want to take this patch, otherwise we would be just adding more and more
    > > to the kernel log.
    > >
    > > If you programatically want to find this out, use libudev or listen to
    > > the dbus messages for new devices, don't watch the kernel log messages.
    > Hmm, but when you go through your syslog/dmesg lines especially in case of
    > USB devices which you swap in and out quite often, it is too late to lookup
    > some file elsewhere which relates to *current* device. The information
    > is lost already if you changed device meanwhile. You just realize USB disk
    > disconnected but you have not way find out except from the log files what
    > speed did it use. In case of USB3 devices capable of lower speeds it is
    > quite important. Some just claim USB3 capabilities (on the package box)
    > but in real, always end up at high-speed only.
    > For me testing several USB disks, USB to SATA bridges, host controllers,
    > kernel command-lines ... it is way to much work. Having the USB debug
    > enabled, especially XHCI_HCD_DEBUG gives on the other had too much output
    > for daily use but as this is all stuff prone to fail somewhere and at some
    > point I keep it enabled.
    > I don't think it clutters syslog nor that it adds significant extra size
    > to the output. It would save people from enabling debug just because of this.
    > And no, average linux user never never lookup sysfs nor use libudev, really.
    > Still, the link speed is of interest to everybody fiddling with the stuff
    > and wondering why the damn thing is so slow or why did it disconnect. It gives
    > an answer or at least a hint.

    But the kernel _already_ logs a message listing new USB devices along
    with their speed. In fact, it does this even if the ANNOUNCE config
    option isn't set.

    Alan Stern

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