On Mon, Jul 02, 2012 at 02:56:03PM -0700, Sarah Sharp wrote: > 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 would probably help, right? > > 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. power/ is controlled by the driver core, not by the busses or drivers, so I don't think you could get access to that directory to do that, right? Even if you could, it's really a USB-only option, so just stick it in the USB device directory. thanks, greg k-h -- 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
