uinput: How to use force feedback?

uinput: How to use force feedback?

[Manuel Reimer]

Hello,

I have an existing uinput driver, which itself sits on an open device 
with a blocking read(), waiting for events to come in. Every event is 
translated to a key code and then sent to uinput.

My next step would be to pass through force feedback information, but I 
don't really understand how I should do this.

As far as I can see, the "uninput device" itself sends events in this 
case. But my main loop is already blocked by the "read", I use to get 
device events.

I see two possible solutions:
- "Somehow", I should be able to get "blocking read" from two open 
devices. As far as I found out, so far, "select" should be the right 
command to do this?
- I could start two threads. One blocked by the "device events" and one 
by the "uinput events".

Which one would you recommend? Is uinput/ioctl thread safe? Is the 
second thread a good idea or is the communication, coming from uinput, 
such "low traffic", that it doesn't delay key handling in a relevant way?

Thank you very much in advance

Manuel

Re: uinput: How to use force feedback?

[Elias Vanderstuyft]

On Sun, Jan 17, 2016 at 2:27 PM, Manuel Reimer
<Manuel.Spam@nurfuerspam.de> wrote:
> Hello,
>
> I have an existing uinput driver, which itself sits on an open device with a
> blocking read(), waiting for events to come in. Every event is translated to
> a key code and then sent to uinput.
>
> My next step would be to pass through force feedback information, but I
> don't really understand how I should do this.

Concerning this,
the following may give you an example how to read incoming FF events on uinput:
https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341

A good while ago I started working on FF support for
the uinput user-space library libsuinput, (and also for python-uinput,)
but I have to clean up some things before I can merge it to:
https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341

Thanks,
Elias

Re: uinput: How to use force feedback?

[Elias Vanderstuyft]

On Sun, Jan 17, 2016 at 4:46 PM, Elias Vanderstuyft <elias.vds@gmail.com> wrote:
> On Sun, Jan 17, 2016 at 2:27 PM, Manuel Reimer
> <Manuel.Spam@nurfuerspam.de> wrote:
>> Hello,
>>
>> I have an existing uinput driver, which itself sits on an open device with a
>> blocking read(), waiting for events to come in. Every event is translated to
>> a key code and then sent to uinput.
>>
>> My next step would be to pass through force feedback information, but I
>> don't really understand how I should do this.
>
> Concerning this,
> the following may give you an example how to read incoming FF events on uinput:
> https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341
>
> A good while ago I started working on FF support for
> the uinput user-space library libsuinput, (and also for python-uinput,)
> but I have to clean up some things before I can merge it to:
> https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341

Sorry for the typo, here is the correct link:
https://github.com/tuomasjjrasanen/python-uinput/tree/master/libsuinput

Re: uinput: How to use force feedback?

[Tuomas Räsänen]

On Sun, Jan 17, 2016 at 5:46 PM, Elias Vanderstuyft <elias.vds@gmail.com> wrote:
>
> A good while ago I started working on FF support for
> the uinput user-space library libsuinput, (and also for python-uinput,)
> but I have to clean up some things before I can merge it to:
> https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341
>

Patches are more than welcome! (I'm the author of libsuinput, happy to
see someone actually uses it without python-uinput, but I welcome
patches to python-uinput as well).

-- 
Tuomas

Re: uinput: How to use force feedback?

[Manuel Reimer]

On 01/17/2016 04:46 PM, Elias Vanderstuyft wrote:
> Concerning this,
> the following may give you an example how to read incoming FF events on uinput:
> https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341

Tried that and I'm pretty close to giving up...

I've added the following to my uinput init function:

   // Set up force feedback parameters
   ret = ioctl(fd, UI_SET_EVBIT, EV_FF);

   ret = ioctl(fd, UI_SET_FFBIT, FF_PERIODIC);
   ret = ioctl(fd, UI_SET_FFBIT, FF_RUMBLE);
   ret = ioctl(fd, UI_SET_FFBIT, FF_GAIN);
   ret = ioctl(fd, UI_SET_FFBIT, FF_SQUARE);
   ret = ioctl(fd, UI_SET_FFBIT, FF_TRIANGLE);
   ret = ioctl(fd, UI_SET_FFBIT, FF_SINE);

 From my device handling thread, I'm starting a separate thread to 
handle the opposite direction of communication. Plan is to do blocking 
read from the open uinput device. I open the device with O_RDWR to be 
able to read and write. The "rumble thread" starts with:

   pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
   pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL);

   struct input_event event;

   while (1) {
     ssize_t n = read(args->fduinput, &event, sizeof(event));
     printf("n: %d\n", n);

Everything beyond this never executes. The read blocks forever.

And even worse: If the read blocks, my "driver", and all programs 
connected to my input device, are deadlocked. No chance to kill them.

And to be honest: After three hours of debugging I'm kind of sick of 
rebooting my machine over and over again.

Any chance to get some hint?

Thanks in advance

Manuel

Re: uinput: How to use force feedback?

[Manuel Reimer]

Hello,

I just want to add here, that I found the reason for this problem.

It is required that the ff_effects_max field of the uinput_user_dev 
struct is set. Without doing this everything just hangs...

Best regards,

Manuel

On 02/05/2016 04:54 PM, Manuel Reimer wrote:
> On 01/17/2016 04:46 PM, Elias Vanderstuyft wrote:
>> Concerning this,
>> the following may give you an example how to read incoming FF events
>> on uinput:
>> https://github.com/xboxdrv/xboxdrv/blob/8e9fb6b40df568d4e4af63e80518366ee4aa5fd3/src/linux_uinput.cpp#L341
>>
>
> Tried that and I'm pretty close to giving up...
>
> I've added the following to my uinput init function:
>
>    // Set up force feedback parameters
>    ret = ioctl(fd, UI_SET_EVBIT, EV_FF);
>
>    ret = ioctl(fd, UI_SET_FFBIT, FF_PERIODIC);
>    ret = ioctl(fd, UI_SET_FFBIT, FF_RUMBLE);
>    ret = ioctl(fd, UI_SET_FFBIT, FF_GAIN);
>    ret = ioctl(fd, UI_SET_FFBIT, FF_SQUARE);
>    ret = ioctl(fd, UI_SET_FFBIT, FF_TRIANGLE);
>    ret = ioctl(fd, UI_SET_FFBIT, FF_SINE);
>
>  From my device handling thread, I'm starting a separate thread to
> handle the opposite direction of communication. Plan is to do blocking
> read from the open uinput device. I open the device with O_RDWR to be
> able to read and write. The "rumble thread" starts with:
>
>    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
>    pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL);
>
>    struct input_event event;
>
>    while (1) {
>      ssize_t n = read(args->fduinput, &event, sizeof(event));
>      printf("n: %d\n", n);
>
> Everything beyond this never executes. The read blocks forever.
>
> And even worse: If the read blocks, my "driver", and all programs
> connected to my input device, are deadlocked. No chance to kill them.
>
> And to be honest: After three hours of debugging I'm kind of sick of
> rebooting my machine over and over again.
>
> Any chance to get some hint?
>
> Thanks in advance
>
> Manuel
>
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Re: uinput: How to use force feedback?

[Elias Vanderstuyft]

On Fri, Feb 5, 2016 at 9:58 PM, Manuel Reimer
<Manuel.Spam@nurfuerspam.de> wrote:
> Hello,
>
> I just want to add here, that I found the reason for this problem.
>
> It is required that the ff_effects_max field of the uinput_user_dev struct
> is set. Without doing this everything just hangs...

Indeed, the uinput_user_dev struct should be properly initialized.
I ran into the same problem, and I created some patches which may fix the hangs:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/input/ff-core.c?id=33b96d934902f96e901b72ac18bbc47afad1ac20
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/input/misc/uinput.c?id=daf6cd0c1829c48cba197bd87d57fc8bf3f65faa

Which kernel version are you using?
The first patch is already in version 4.4.

Glad you got it working now,
Elias

Re: uinput: How to use force feedback?

[Manuel Reimer]

On 02/10/2016 10:41 PM, Elias Vanderstuyft wrote:
> Which kernel version are you using?
> The first patch is already in version 4.4.

Currently 4.3.3. Self-built to have a small patch which makes PS4 
controller bluetooth binding possible (will be in kernel in version 4.5).

Rumble seems to be a problem with uinput in general. For example it is 
pretty easy to create "non-killable" processes if fftest is still 
running when the uinput daemon is killed. Not much fun to debug 
something like this, so I finally disabled my rumble support.

> Glad you got it working now,

Partially but not really solving my problem. Still working on it.

Manuel