On Tue, 9 Aug 2016, Muni Sekhar wrote: > Hello, > > > At some stage USB peripherals negotiate how much current they are > allocated. For e.g. USB2 starts at 100mA and then negotiating 500mA. > I presume similar happens for USB3 with different amount of current available. > > > Is there a mechanism for driver to tell the hardware what current limit to set? No, there isn't. Well, some hardware may have such a mechanism, but I haven't heard of any examples. And Linux isn't set up to use it. There is a mechanism for the host system to tell the device how much current to limit itself to. The host tells the device which configuration to install; each configuration has a current limit described by the bMaxPower field in the config descriptor. However, drivers usually do not select or install configurations. 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
