On Fri 2016-09-09 13:31:10, Rafał Miłecki wrote: > On 9 September 2016 at 13:05, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, Sep 09, 2016 at 05:34:40PM +0800, Peter Chen wrote: > >> 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 > > > > Ugh, I thought I had seen something like this before... > > > > Rafał, can you just use this in-kernel code instead? > > I really don't think I can because of all the reasons I carefully > listed in the commit message. > > Have you took a look at that simple driver? It does nothing I need. > Its design doesn't allow implementing features I clearly listed in the > commit message. In any case, the new driver should probably go near the old one, at the very least. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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
