On Thu, Sep 08, 2016 at 06:08:24PM +0200, Rafał Miłecki wrote: > From: Rafał Miłecki <rafal@xxxxxxxxxx> > > This commit adds a new trigger responsible for turning on LED when USB > device gets connected to the selected USB port. This can can useful for > various home routers that have USB port(s) and a proper LED telling user > a device is connected. > > The trigger gets its documentation file but basically it just requires > enabling it and selecting USB ports (e.g. echo 1 > ports/usb1-1). > > There was a long discussion on design of this driver. Its current state > is a result of picking them most adjustable solution as others couldn't > handle all cases. > > 1) It wasn't possible for the driver to register separated trigger for > each USB port. Some physical USB ports are handled by more than one > controller and so by more than one USB port. E.g. USB 2.0 physical > port may be handled by OHCI's port and EHCI's port. > It's also not possible to assign more than 1 trigger to a single LED > and implementing such feature would be tricky due to syncing triggers > and sysfs conflicts with old triggers. > > 2) Another idea was to register trigger per USB hub. This wouldn't allow > handling devices with multiple USB LEDs and controllers (hubs) > controlling more than 1 physical port. It's common for hubs to have > few ports and each may have its own LED. > > This final trigger is highly flexible. It allows selecting any USB ports > for any LED. It was also modified (compared to the initial version) to > allow choosing ports rather than having user /guess/ proper names. It > was successfully tested on SmartRG SR400ac which has 3 USB LEDs, > 2 physical ports and 3 controllers. > > Another planned feature is support for LED reacting to the USB activity. > This can be implemented with another sysfs file for setting mode. The > default mode wouldn't change so there won't be ABI breakage and such > feature can be safely implemented later. > It has such driver at: drivers/usb/common/led.c -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
