is there a reason "usbhid.quirks" parameter is not root writable?

Greg KH greg at
Thu Nov 12 20:31:06 EST 2015

On Thu, Nov 12, 2015 at 08:02:00PM -0500, Valdis.Kletnieks at wrote:
> But to answer Robert's question:  I suspect that it's mode 0444 so you can
> read the current list, but changing the list after modprobe time is for
> some reason problematic.  Having said that, I admit I haven't looked at
> the source deep enough to find the exact reason. It's probably something
> subtle, because simply adding an ID to a list of IDs shouldn't be that
> hard....

To do that you now need to keep a separate dynmic list of ids that you
also need to check, and clean up when shut down, it's not as "simple" as
you might think.  Not impossible, we do it for lots of other places, and
the hid core does handle dynamic quirks as I pointed out, so you should
be fine.

If people have questions about this, please ask them on the linux-input
mailing list, where the HID developers are at.


greg k-h

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