Re: is it possible to temporarily not let user mode get hid input event

[David Herrmann <dh.herrmann@gmail.com>]

Hi

On Mon, Feb 24, 2014 at 12:20 PM, loody <miloody@gmail.com> wrote:
> hi David:
>
> 2014-02-23 23:16 GMT+08:00 David Herrmann <dh.herrmann@gmail.com>:
>> Hi
>>
>> On Sun, Feb 23, 2014 at 7:52 AM, loody <miloody@gmail.com> wrote:
>>> hi David:
>>>
>>> Thanks for your suggestion.
>>> 2014-02-23 0:56 GMT+08:00 David Herrmann <dh.herrmann@gmail.com>:
>>>> Hi
>>>>
>>>> On Sat, Feb 22, 2014 at 5:35 PM, loody <miloody@gmail.com> wrote:
>>>>> hi all:
>>>>> is there any kernel hid module parameter or test program can
>>>>> temporarily not letting user mode program not receiving hid event?
>>>>> 1. My hid kos are still inserted in.
>>>>> 2. the kernel usb driver is working well; that mean kernel usb driver
>>>>> still handle interrupt transaction.
>>>>>
>>>>> I just not want user mode program see the hid event for a while,
>>>>
>>>> For each connected HID device, there is a driver bound to it that
>>>> reads the events and forwards them to HID core. What you can do, is to
>>>> unbind a driver on a given device:
>>>>   echo "<your-device-name>" >/sys/bus/hid/drivers/<driver-name>/unbind
>>>> The device-name is the directory name in:
>>>>   /sys/bus/hid/devices/
>>>> The driver name is usually "hid-generic" but can be figured out for
>>>> each device by looking at the "driver" symlink in it's directry.
>>>> However, this is *really* just meant for debugging. This is not
>>>> recommended for anything serious. There is no support for that and if
>>>> you don't know what all this does, you shouldn't use it.
>>>>
>>>> There is no proper way to disable a single device in the kernel.
>>>> User-space is supposed to control device-access so we probably won't
>>>> add such features to the kernel. If you describe your use-case in more
>>>> details, we can try to give hints how to get that working.
>>>
>>> Sorry for not describing our situation clearer previously,
>>>
>>> The problem we met like below
>>> a. once plug in usb hid mouse and fast moving mouse
>>> b. the screen will get blur.
>>>
>>> We want to know whether the screen blur is caused by
>>> 1. the interrupt frequency of usb mouse is too high for our embedded
>>> system that make video decode slow
>>> 2. something wrong between hw cursor and video overlay.
>>>
>>> if we can deceive user mode program there is no mouse event, but
>>> kernel usb level still get hid interrupt transaction.
>>> We may clarify whether above 1) conclusion is correct.
>>>
>>> Appreciate your kind help :-)
>>
>> You can unload the HID driver as described above, but that's unlikely
>> to fix any interrupt issues. How about you compile your kernel without
>> usbhid support? (CONFIG_USB_HID)
>
> BTW, is there any fake virtual mouse to use?
> That mean user doesn't plug in any usb hid mouse, but user mode
> program can receive hid mouse event?

Yes. For instance, you can run ./samples/uhid/uhid-example.c via ssh
to emulate a mouse. ssh keyboard input can then be used to generate
mouse-movement events.

Thanks
David