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SubjectRe: [PATCH v3] Documentation: Input: Add uinput documentation
On Mon, Mar 27, 2017 at 11:06:11AM +1000, Peter Hutterer wrote:
> On Sun, Mar 26, 2017 at 01:48:12PM -0300, Marcos Paulo de Souza wrote:
> > Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> > ---
> > v2 -> v3:
> > Changes in libevdev's description (suggested by Peter)
> > Added uinput version check when using the old interface (suggested by Peter)
> > Removed section numbers from sections, sphinx creates these indexes
> > (suggestion by Jon)
> >
> > v1 -> v2:
> > Changes all over the place, including better descriptions (suggested by Peter)
> > Added comments about the need of a sleep call (suggested by Peter)
> >
>
>
> [...]
>
> tested mouse/keyboard - works as expected, thanks. I found it slightly
> confusing though that the mouse example wasn't wrapped in main() but still had a
> return 0 at the bottom. This code will never change once it's in the doc, so
> I'm not sure skipping things is really that useful here.

True, I'll "complete" the code in the next submission.

>
> > +uinput old interface
> > +--------------------
> > +
> > +Before uinput version 5, there wasn't a proper ioctl to setup a virtual device.
> > +In this case, the user neesa to fill a different struct and call write o the
> > +uinput file descriptor to configure the new uinput device.
> > +
> > +.. code-block:: c
> > +
> > + #include <linux/uinput.h>
> > +
> > + /* emit function is identical to of the first example */
> > +
> > + struct uinput_user_dev uud;
> > + int version;
> > +
> > + fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > + ioctl(fd, UI_GET_VERSION, &version);
> > +
> > + if (version < 5) {
>
> this won't work on all kernels. UI_GET_VERSION was added in version 4, on
> kernels before you get rc == -1 and errno EINVAL. You can only check
> for >= 4. Please make sure the example compiles and works on an older
> kernel, otherwise there's no point shipping it.

OK, noting here.

>
> Cheers,
> Peter
>
> > + /*
> > + * the ioctls below enables the to be created device to key
> > + * events, in this case the space key
> > + */
> > + ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > + ioctl(fd, UI_SET_KEYBIT, KEY_SPACE);
> > +
> > + memset(&uud, 0, sizeof(uud));
> > + snprintf(uud.name, UINPUT_MAX_NAME_SIZE, "uinput old interface");
> > + write(fd, &uud, sizeof(uud));
> > +
> > + ioctl(fd, UI_DEV_CREATE);
> > +
> > + /*
> > + * On UI_DEV_CREATE the kernel creates the device nodes for this device.
> > + * Insert a pause so that userspace has time to detect, initialize the
> > + * new device, and can start to listen to events from this device
> > + */
> > + sleep(1);
> > +
> > + /* key press, report the event, send key release, and report again */
> > + emit(EV_KEY, KEY_SPACE, 1);
> > + emit(EV_SYN, SYN_REPORT, 0);
> > + emit(EV_KEY, KEY_SPACE, 0);
> > + emit(EV_SYN, SYN_REPORT, 0);
> > +
> > + ioctl(fd, UI_DEV_DESTROY);
> > + }
> > +
> > + close(fd);
> > +
> > + return 0;
> > +
> > --
> > 2.9.3
> >

--
Thanks,
Marcos

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