Hello. I've been told this is the right place to ask, correct me if I'm wrong. I don't think the ability to limit a port to 100mA current draw is exposed by the drivers. The use-case for this is to avoid a battery powered device such as a phone from draining the battery of a laptop while travelling. Data transfer is all that's needed here. It is also wasteful to charge one battery from another. In the interests of saving energy, and prolonging battery-life, please could a mechanism to restrict to 100mA be implemented. I could then set up an automatic ACPI response to AC power to allow 500mA and charge the phone, but battery-to-battery transfer is inefficient and should be avoided. Apparently USB ports can be disabled, and when this occurs no power is supplied. However, I think the ability to disable a port is also not exposed by the USB drivers. There are many use-cases for this. In the interest of saving electricity, it is desirable to unplug unused devices. USB ports can be plugged only about 1500 times before they ware out, and sometimes the ports are fairly inaccessible behind the base unit of a computer. Some badly designed devices will often need resetting by physically replugging. If a USB device is plugged into a host device that is remotely monitored, it is not possible to physically reconnect the device. A less serious and more fun use-case is the automation of USB 'decorations', which simply use the 5V power supply. It seems an oversight that USB devices cannot be programmatically disconnected and reconnected in GNU/Linux OSes. I would appreciate it if they could, if possible, and I know for sure that others would too. It has been suggested that I should send a patch in, but I am no kernel or driver developer, and I'm better off contributing to Free software projects that are achievable at my skill-level. If you want me to file these 2 issues/feature-requests somewhere, tell me where and I will. Thanks and best regards, James Haigh. -- 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
