1

This is an issue I have for the second time now: basically, an USB based device reports some wrong numbers for "HID_MAX_USAGES", resulting in the kernel giving an error message and the device not working. I had this issue with an Sharkoon Drakonia mouse a couple of years ago, and while the mouse is supported by the linux kernel by now, the detachable keyboard of my new Medion P2213T is not. But there are all kinds of devices out there with this issue, have a look at this bug report for more details.

From what I have read by now, there are different ways to work around this issue: The one most people seem to use is to rebuild the kernel, after changing "HID_MAX_USAGES" in "include/linux/hid.h" to a higher value (mostly around 64k). While this works quite well, the asigned developer in the bug report I linked above pointed out it will increase memory usage, and this will lead to bad perfomance especially on a low end tablet device. Also, you will have to rebuild the kernel every time you want a security update and you can not use your distros automatic kernel update system (this is really the worst part)...

The second approach would be thinking about fixing the USB HID Report Descriptor, as usually these high values are not justified anyways. I think there are two ways for this again, fixing it on the device firmware itself, or adding it to some kind of whitelist in the kernel source code to overwrite the value. But it is hard to find more info on both ways.

So it boils down to these questions:

Where would I ask for adding the detachable keyboard to this "whitelist"? What data should I attach? I know it should be possible, because my Sharkoon mouse is supported by up-to-date kernels by now.

Are there other ways making the kernel support my device, without disabling automatic kernel updates?

Thanks!

  • Keyboard? Can't you borrow/buy some other keyboard for a while? The time to keep up with all the problems of a kernel compile are really much more expensive than any keyboard IMhO. – user79743 Aug 23 '15 at 23:11
  • tabtech.de/wp-content/uploads/2014/09/… it is this kind of device, I used a USB keyboard to set up my system, but it really takes away the usefullness the dock. But I understand your thoughts, rebuilding the kernel is really annoying and in fact I did not manage to compile a working one on Fedora 22... Had it kinda working with an Ubuntu 14.04 based distro before, with huge oerformance issues though... I would prefer a different solution as well! – elephantery Aug 23 '15 at 23:22
  • Actually, I guess I found the source code of the patch enabling support of my Sharkoon mouse: comments.gmane.org/gmane.linux.kernel.input/30299 – elephantery Aug 24 '15 at 0:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.