Hi, On Fri, Mar 13, 2015 at 2:37 AM, Timo Teras <timo.teras@xxxxxx> wrote: > Hi, > > I'm trying to write userland driver for an input controller - > basically a macrokeyboard: some keys act like regular keys, and some > are not really described in the descriptor so it needs custom parser. > It has also extra commands to set/blink LEDs, etc. > > I'd need exclusive access to it. Mainly because some of the keys emit > normal looking presses and I would not like them to be fed into the > input system when my application is running. As side effect I get also > in dmesg errors like "input input16: event field not found" due to this. > > Now this is of course doable with libusb, not using kernel hid > subsystem, and reimplementing the relevant hid bits (or using some of > the existing hid libraries doing this). But this sounds a bit overkill > and hidraw seems to be exactly for this kind of use case. > > The only problem is that I was not able to find a 'grab device' type of > functionality in hidraw. Basically equivalent of EVIOCGRAB in input > subsystem. Something that would make sure the reports come only to > hidraw device. > > Would it make sense to implement something like this for hidraw? I am not a big fan of this idea. Simply because sensitive information like key press should not be handled in user space. Really, we already have keyboards macro support in the kernel (see drivers/hid/hid-roccat*) and I think you should consider doing your driver in the kernel. > > As an alternative I think we could have hid-rawonly driver, that would > by default bind to nothing. And when bound, would connect to the hid > device with HID_CONNECT_HIDRAW flag only. I could then in userland > rebind the device from hid-generic to hid-rawonly. That could work (make a special driver and use HID_CONNECT_HIDRAW), but that's a terrible idea and will be refused I guess. Users expects their keyboard to be working everywhere, even at boot and in the console. By doing so, you will just break existing keyboards. > > Or finally, to implement a full kernel side driver it. But I'd > rather not go there. Especially since the device has multiple leds, and > the input system allows only limited leds. (The leds could be exported > as led devices, but then I'd need more userland logic to figure out > which led devices map to which input device.) No, that's not true. If you have LEDs, then use the LED class and then user space deal with the LEDs. If the LEDs are not standard, then you will need userspace tools to access them so I don't think it is a problem. Standard LEDs will be handled properly through the input node (CAPS Lock, Ver Num, etc...). The good side of having your driver in the kernel is also less maintenance, and less pain for the users. Once it hits mainline, users will have a functional keyboard without having to rely on anything else. For you, if some interface change, you will have less head aches. If you *really* don't want to work in the kernel, you should simply ignore the generic keys in your driver and work only on the special keys macros that you want to support. Cheers, Benjamin > > Thoughts? > > Thanks, > Timo > -- > To unsubscribe from this list: send the line "unsubscribe linux-input" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
