On 25 August 2016 at 10:03, Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx> wrote: > On 08/24/2016 07:52 PM, 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 specified 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 >> specifying USB port in a Linux format (e.g. echo 1-1 > new_port). >> >> During work on this trigger there was a plan to add DT bindings for it, >> but there wasn't an agreement on the format yet. This can be worked on >> later, a sysfs interface is needed anyway for platforms not using DT. >> >> Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx> >> --- >> V2: Trying to add DT support, idea postponed as it will take more time >> to discuss the bindings. >> V3: Fix typos in commit and Documentation (thanks Jacek!) >> Use "ports" sysfs file for adding and removing USB ports (thx Jacek) >> Check if there is USB device connected after adding new USB port >> Fix memory leak or two >> V3.5: Fix e-mail address (thanks Matthias) >> Simplify conditions in usbport_trig_notify (thx Matthias) >> Make "ports" a subdirectory with file per port, to match one value >> per file sysfs rule (thanks Greg) >> As "ports" couldn't be used for adding and removing ports anymore, >> there are now "new_port" and "remove_port". Having them makes this >> API also common with e.g. pci and usb buses. > > > Now writing new_port with "1-1" produces a file named "1-1" in the > ports directory with 000 permissions. I think that what Greg had > on mind by referring to "one value per file" rule was a set of > files representing ports, like "1-1 1-2 2-1", and each file should be > readable/writeable. > > For instance "echo 1 > 1-1" would enable the trigger for the port 1-1 > and "echo 0 > 1-1" would disable it. The problem is that we don't know > the number of required ports at compilation time and the sysfs > attributes would have to be dynamically created on driver instantiation. > What is more, as the USB ports can dynamically appear/disappear in the > system, the files would have to be created/removed accordingly during > LED class device lifetime, which is not the best design for the sysfs > interface I think. > > Therefore, maybe it would be good to follow the "triggers" sysfs > attribute pattern, where it lists the available LED triggers? > > The question is whether there is some mechanism available for > notifying addition/removal of a USB port? Every port is part of some hub and every hub (even root one) is a USB device. So I could just get struct usb_device and check its "maxchild" property. If e.g. I get USB device "1-1" with maxchild 4, I know there are: 1-1.1 1-1.2 1-1.3 1-1.4 So the sysfs structure you suggested would be possible, I just don't know if it's preferred one or not. Confirmation: yes, right now I create simple files with chmod 000 for every port added to the usbport observable list. > Also a description of the device connected to the port would be a nice > feature, however I am not certain about the feasibility thereof. What kind of description do you mean? Where should it be used / where should it appear? -- Rafał -- 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
