On Mon, Jun 25, 2012 at 04:58:29PM -0700, Greg KH wrote: > On Mon, Jun 25, 2012 at 03:39:59PM -0700, Sarah Sharp wrote: > > USB 3.0 devices may optionally support a new feature called Latency > > Tolerance Messaging. If both the xHCI host controller and the device > > support LTM, it should be turned on in order to give the system hardware > > a better clue about the latency tolerance values of its PCI devices. > > > > LTM is disabled by default on enumeration or after device reset. Once a > > Set Feature request to enable LTM is received, the USB 3.0 device will > > begin to send LTM updates as its buffers fill or empty, and it can > > tolerate more or less latency. > > > > Make the USB core enable LTM after the device is reset. The USB 3.0 > > spec, section C.4.2 says that LTM should be disabled just before the > > device is placed into suspend. Then the device will send an updated LTM > > notification, so that the system doesn't think it should remain in an > > active state in order to satisfy the latency requirements of the > > suspended device. > > > > Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> > > --- > > drivers/usb/core/hub.c | 66 +++++++++++++++++++++++++++++++++++++++++++++-- > > 1 files changed, 63 insertions(+), 3 deletions(-) > > I know you added support for the parsing of the device descriptor in > lsusb, but would it also be nice to add this to a sysfs file as well, > for those programs that don't want to parse the bits in the descriptor > (or don't know how to?) So you want a sysfs file that just indicates whether the device supports LTM? > That's not saying there's anything wrong with this patch at all, but how > about an add-on patch adding that? Ok, sure. Maybe the sysfs file could live in the power directory? Like /sys/bus/usb/devices/../power/ltm_supported? It could return 0/1 or no/yes. Sarah Sharp -- 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
