On Wed, 11 Jan 2017, Felipe Balbi wrote: > Hi, > > Todd Brandt <todd.e.brandt@xxxxxxxxxxxxxxx> writes: > > On Mon, 2017-01-09 at 09:44 +0100, Oliver Neukum wrote: > >> On Fri, 2017-01-06 at 16:45 -0800, Todd Brandt wrote: > >> > Add a kernel parameter that replaces the USB_RESUME_TIMEOUT > >> > and other hardcoded delay numbers with the USB spec minimums. > >> > >> Hi, > >> > >> the problem with that is that distros cannot use it. It is obviously > >> better than nothing but it seems to me that we can do better than an > >> all or nothing option here. > > > > Well my main purpose in getting this out there is to get the seed > > planted for further optimization. The focus right now is just advanced > > users who want to optimize their personal machines. > > > > But you're right, it wouldn't be responsible to enable this feature by > > default in a distro like android or chromium. > > > >> For example it would be much safer to enable this for hubs of the > >> first level and internal devices. > > I disagree. I think it's only safe to do so for devices known to be > compliant. This would mean, we need to start building a whitelist of > compliant devices and only for such devices should we enforce compliant > behavior. > > > Is there a universal way to reliably determine which USB devices are > > internal? > > not that I know of :-( These devices are enumerated the same way as any > other. We have udev->removable. It's based on information provided by the firmware, so it may not be extremely reliable. Generally, you could assume that if udev->removable is set and udev's parent is the root hub then udev is an internal device. On the other hand, I don't know any reason to assume that internal devices are more compliant as regards reset/resume timing than any other devices. 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
