[PATCH v2] Documentation: Input: Add uinput documentation

[PATCH v2] Documentation: Input: Add uinput documentation

[Marcos Paulo de Souza]

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
---
 Documentation/input/uinput.rst | 196 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 196 insertions(+)
 create mode 100644 Documentation/input/uinput.rst

diff --git a/Documentation/input/uinput.rst b/Documentation/input/uinput.rst
new file mode 100644
index 0000000..eb79b77
--- /dev/null
+++ b/Documentation/input/uinput.rst
@@ -0,0 +1,196 @@
+=============
+uinput module
+=============
+
+Introduction
+============
+
+uinput is a kernel module that makes possible to create and handle input devices
+from userspace. By writing to the module's /dev/uinput (or /dev/input/uinput), a
+process can create a virtual device with specific capabilities.
+Once created, the process can send events through that virtual device.
+
+Interface
+=========
+
+::
+
+  linux/uinput.h
+
+The uinput header defines ioctls to create, setup and destroy virtual devices.
+
+libevdev
+========
+
+libevdev is a wrapper library for evdev devices, making uinput setup easier
+by skipping a lot of ioctl calls. When dealing with uinput, libevdev is the best
+alternative over accessing uinput directly, and it is less error prone.
+
+For examples and more information about libevdev:
+https://cgit.freedesktop.org/libevdev
+
+Examples
+========
+
+1.0 Keyboard events
+-------------------
+
+This first example shows how to create a new virtual device and how to send a
+key event. All default imports and error handlers were removed for the sake of
+simplicity.
+
+.. code-block:: c
+
+   #include <linux/uinput.h>
+
+   int fd;
+
+   void emit(int type, int code, int val)
+   {
+        struct input_event ie;
+
+        ie.type = type;
+        ie.code = code;
+        ie.value = val;
+        /* below timestamp values are ignored */
+        ie.time.tv_sec = 0;
+        ie.time.tv_usec = 0;
+
+        write(fd, &ie, sizeof(ie));
+   }
+
+   int main() {
+        struct uinput_setup usetup;
+
+        fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
+
+        /* 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(&usetup, 0, sizeof(usetup));
+        usetup.id.bustype = BUS_USB;
+        usetup.id.vendor = 0x1234; /* sample vendor */
+        strcpy(usetup.name, "Example device");
+
+        ioctl(fd, UI_DEV_SETUP, &usetup);
+        ioctl(fd, UI_DEV_CREATE);
+
+        /* UI_DEV_CREATE causes the kernel to create 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
+         **/
+
+        /* 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;
+   }
+
+2.0 Mouse movements
+-------------------
+
+This example shows how to create a virtual device that behaves like a physical
+mouse.
+
+.. code-block:: c
+
+    #include <linux/uinput.h>
+
+    /* emit function is identical to of the first example */
+
+    struct uinput_setup usetup;
+    int i = 50;
+
+    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
+
+    /* enable mouse button left and relative events */
+    ioctl(fd, UI_SET_EVBIT, EV_KEY);
+    ioctl(fd, UI_SET_KEYBIT, BTN_LEFT);
+
+    ioctl(fd, UI_SET_EVBIT, EV_REL);
+    ioctl(fd, UI_SET_RELBIT, REL_X);
+    ioctl(fd, UI_SET_RELBIT, REL_Y);
+
+    memset(&usetup, 0, sizeof(usetup));
+    usetup.id.bustype = BUS_USB;
+    usetup.id.vendor = 0x1234; /* sample vendor */
+    strcpy(usetup.name, "Example device");
+
+    ioctl(fd, UI_DEV_SETUP, &usetup);
+    ioctl(fd, UI_DEV_CREATE);
+
+    /* UI_DEV_CREATE causes the kernel to create 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
+     **/
+
+    /* moves the mouse diagonally, 5 units per axis */
+    while (i--) {
+        emit(EV_REL, REL_X, 5);
+        emit(EV_REL, REL_Y, 5);
+        emit(EV_SYN, SYN_REPORT, 0);
+        usleep(15000);
+    }
+
+    ioctl(fd, UI_DEV_DESTROY);
+    close(fd);
+
+    return 0;
+
+3.0 uinput old interface
+------------------------
+
+Before kernel 4.5, uinput didn't have an ioctl to setup a virtual device. When
+running a version prior to 4.5, the user needs to fill a different struct and
+call write on the uinput file descriptor.
+
+.. code-block:: c
+
+    #include <linux/uinput.h>
+
+    /* emit function is identical to of the first example */
+
+    struct uinput_user_dev uud;
+
+    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
+
+    /* 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);
+
+    /* UI_DEV_CREATE causes the kernel to create 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
+     **/
+
+    /* 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

Re: [PATCH v2] Documentation: Input: Add uinput documentation

[Peter Hutterer]

as usual, reading through these things multiple times means one spots a
couple of different things. sorry about that.

On Fri, Mar 24, 2017 at 12:34:59AM -0300, Marcos Paulo de Souza wrote:
> Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> ---
>  Documentation/input/uinput.rst | 196 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 196 insertions(+)
>  create mode 100644 Documentation/input/uinput.rst
> 
> diff --git a/Documentation/input/uinput.rst b/Documentation/input/uinput.rst
> new file mode 100644
> index 0000000..eb79b77
> --- /dev/null
> +++ b/Documentation/input/uinput.rst
> @@ -0,0 +1,196 @@
> +=============
> +uinput module
> +=============
> +
> +Introduction
> +============
> +
> +uinput is a kernel module that makes possible to create and handle input devices

typo: makes *it* possible.

replace "to create and handle" with "to emulate", the rest is in the next
sentence anyway

> +from userspace. By writing to the module's /dev/uinput (or /dev/input/uinput), a
> +process can create a virtual device with specific capabilities.
> +Once created, the process can send events through that virtual device.
> +
> +Interface
> +=========
> +
> +::
> +
> +  linux/uinput.h
> +
> +The uinput header defines ioctls to create, setup and destroy virtual devices.
> +
> +libevdev
> +========
> +
> +libevdev is a wrapper library for evdev devices, making uinput setup easier
> +by skipping a lot of ioctl calls. When dealing with uinput, libevdev is the best
> +alternative over accessing uinput directly, and it is less error prone.

"libevdev is a wrapper library for evdev devices that provides interfaces to
create uinput devices and send events. libevdev is less error-prone than
accessing uinput directly and should be considered for new software".

> +
> +For examples and more information about libevdev:
> +https://cgit.freedesktop.org/libevdev
> +

Please use https://www.freedesktop.org/software/libevdev/doc/latest/
(which needs a link to the git repo, I'll fix that in a minute)

> +Examples
> +========
> +
> +1.0 Keyboard events
> +-------------------
> +
> +This first example shows how to create a new virtual device and how to send a
> +key event. All default imports and error handlers were removed for the sake of
> +simplicity.
> +
> +.. code-block:: c
> +
> +   #include <linux/uinput.h>
> +
> +   int fd;
> +
> +   void emit(int type, int code, int val)
> +   {
> +        struct input_event ie;
> +
> +        ie.type = type;
> +        ie.code = code;
> +        ie.value = val;
> +        /* below timestamp values are ignored */
> +        ie.time.tv_sec = 0;
> +        ie.time.tv_usec = 0;
> +
> +        write(fd, &ie, sizeof(ie));
> +   }
> +
> +   int main() {
> +        struct uinput_setup usetup;
> +
> +        fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> +
> +        /* the ioctls below enables the to be created device to key
> +         * events, in this case the space key
> +         **/

the comment terminator doesn't look right

> +        ioctl(fd, UI_SET_EVBIT, EV_KEY);
> +        ioctl(fd, UI_SET_KEYBIT, KEY_SPACE);
> +
> +        memset(&usetup, 0, sizeof(usetup));
> +        usetup.id.bustype = BUS_USB;
> +        usetup.id.vendor = 0x1234; /* sample vendor */

add a sample product id too please

> +        strcpy(usetup.name, "Example device");
> +
> +        ioctl(fd, UI_DEV_SETUP, &usetup);
> +        ioctl(fd, UI_DEV_CREATE);
> +
> +        /* UI_DEV_CREATE causes the kernel to create the device nodes for this

"On UI_DEV_CREATE the kernel creates the device nodes..."

> +         * 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
> +         **/

the comment terminator doesn't look right

note: the actual pause is missing now :)

> +
> +        /* 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);

come to think of it, you probably need a pause here too, iirc a caller may
get ENODEV before reading the key events otherwise.

> +
> +        ioctl(fd, UI_DEV_DESTROY);
> +        close(fd);
> +
> +        return 0;
> +   }
> +
> +2.0 Mouse movements
> +-------------------
> +
> +This example shows how to create a virtual device that behaves like a physical
> +mouse.
> +
> +.. code-block:: c
> +
> +    #include <linux/uinput.h>
> +
> +    /* emit function is identical to of the first example */
> +
> +    struct uinput_setup usetup;
> +    int i = 50;
> +
> +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> +
> +    /* enable mouse button left and relative events */
> +    ioctl(fd, UI_SET_EVBIT, EV_KEY);
> +    ioctl(fd, UI_SET_KEYBIT, BTN_LEFT);
> +
> +    ioctl(fd, UI_SET_EVBIT, EV_REL);
> +    ioctl(fd, UI_SET_RELBIT, REL_X);
> +    ioctl(fd, UI_SET_RELBIT, REL_Y);
> +
> +    memset(&usetup, 0, sizeof(usetup));
> +    usetup.id.bustype = BUS_USB;
> +    usetup.id.vendor = 0x1234; /* sample vendor */
> +    strcpy(usetup.name, "Example device");
> +
> +    ioctl(fd, UI_DEV_SETUP, &usetup);
> +    ioctl(fd, UI_DEV_CREATE);
> +
> +    /* UI_DEV_CREATE causes the kernel to create 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
> +     **/
> +
> +    /* moves the mouse diagonally, 5 units per axis */
> +    while (i--) {
> +        emit(EV_REL, REL_X, 5);
> +        emit(EV_REL, REL_Y, 5);
> +        emit(EV_SYN, SYN_REPORT, 0);
> +        usleep(15000);
> +    }
> +
> +    ioctl(fd, UI_DEV_DESTROY);
> +    close(fd);
> +
> +    return 0;
> +
> +3.0 uinput old interface
> +------------------------
> +
> +Before kernel 4.5, uinput didn't have an ioctl to setup a virtual device. When
> +running a version prior to 4.5, the user needs to fill a different struct and
> +call write on the uinput file descriptor.

I think this should really include the version check.

Cheers,
   Peter

> +
> +.. code-block:: c
> +
> +    #include <linux/uinput.h>
> +
> +    /* emit function is identical to of the first example */
> +
> +    struct uinput_user_dev uud;
> +
> +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> +
> +    /* 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);
> +
> +    /* UI_DEV_CREATE causes the kernel to create 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
> +     **/
> +
> +    /* 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
> 

Re: [PATCH v2] Documentation: Input: Add uinput documentation

[Marcos Paulo de Souza]

On Fri, Mar 24, 2017 at 02:39:13PM +1000, Peter Hutterer wrote:
> as usual, reading through these things multiple times means one spots a
> couple of different things. sorry about that.
> 
> On Fri, Mar 24, 2017 at 12:34:59AM -0300, Marcos Paulo de Souza wrote:
> > Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> > ---
> >  Documentation/input/uinput.rst | 196 +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 196 insertions(+)
> >  create mode 100644 Documentation/input/uinput.rst
> > 
> > diff --git a/Documentation/input/uinput.rst b/Documentation/input/uinput.rst
> > new file mode 100644
> > index 0000000..eb79b77
> > --- /dev/null
> > +++ b/Documentation/input/uinput.rst
> > @@ -0,0 +1,196 @@
> > +=============
> > +uinput module
> > +=============
> > +
> > +Introduction
> > +============
> > +
> > +uinput is a kernel module that makes possible to create and handle input devices
> 
> typo: makes *it* possible.
> 
> replace "to create and handle" with "to emulate", the rest is in the next
> sentence anyway

Fixed.

> 
> > +from userspace. By writing to the module's /dev/uinput (or /dev/input/uinput), a
> > +process can create a virtual device with specific capabilities.
> > +Once created, the process can send events through that virtual device.
> > +
> > +Interface
> > +=========
> > +
> > +::
> > +
> > +  linux/uinput.h
> > +
> > +The uinput header defines ioctls to create, setup and destroy virtual devices.
> > +
> > +libevdev
> > +========
> > +
> > +libevdev is a wrapper library for evdev devices, making uinput setup easier
> > +by skipping a lot of ioctl calls. When dealing with uinput, libevdev is the best
> > +alternative over accessing uinput directly, and it is less error prone.
> 
> "libevdev is a wrapper library for evdev devices that provides interfaces to
> create uinput devices and send events. libevdev is less error-prone than
> accessing uinput directly and should be considered for new software".

Much better. Fixed.

> 
> > +
> > +For examples and more information about libevdev:
> > +https://cgit.freedesktop.org/libevdev
> > +
> 
> Please use https://www.freedesktop.org/software/libevdev/doc/latest/
> (which needs a link to the git repo, I'll fix that in a minute)

Fixed.

> 
> > +Examples
> > +========
> > +
> > +1.0 Keyboard events
> > +-------------------
> > +
> > +This first example shows how to create a new virtual device and how to send a
> > +key event. All default imports and error handlers were removed for the sake of
> > +simplicity.
> > +
> > +.. code-block:: c
> > +
> > +   #include <linux/uinput.h>
> > +
> > +   int fd;
> > +
> > +   void emit(int type, int code, int val)
> > +   {
> > +        struct input_event ie;
> > +
> > +        ie.type = type;
> > +        ie.code = code;
> > +        ie.value = val;
> > +        /* below timestamp values are ignored */
> > +        ie.time.tv_sec = 0;
> > +        ie.time.tv_usec = 0;
> > +
> > +        write(fd, &ie, sizeof(ie));
> > +   }
> > +
> > +   int main() {
> > +        struct uinput_setup usetup;
> > +
> > +        fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > +
> > +        /* the ioctls below enables the to be created device to key
> > +         * events, in this case the space key
> > +         **/
> 
> the comment terminator doesn't look right

Fixed.

> 
> > +        ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > +        ioctl(fd, UI_SET_KEYBIT, KEY_SPACE);
> > +
> > +        memset(&usetup, 0, sizeof(usetup));
> > +        usetup.id.bustype = BUS_USB;
> > +        usetup.id.vendor = 0x1234; /* sample vendor */
> 
> add a sample product id too please
Added.

> 
> > +        strcpy(usetup.name, "Example device");
> > +
> > +        ioctl(fd, UI_DEV_SETUP, &usetup);
> > +        ioctl(fd, UI_DEV_CREATE);
> > +
> > +        /* UI_DEV_CREATE causes the kernel to create the device nodes for this
> 
> "On UI_DEV_CREATE the kernel creates the device nodes..."
Fixed.

> 
> > +         * 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
> > +         **/
> 
> the comment terminator doesn't look right
> 
> note: the actual pause is missing now :)

I thought you wanted just the warning, but ok, I added back the sleep
call :)

> 
> > +
> > +        /* 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);
> 
> come to think of it, you probably need a pause here too, iirc a caller may
> get ENODEV before reading the key events otherwise.

We need a sleep call after each emitted event?

> 
> > +
> > +        ioctl(fd, UI_DEV_DESTROY);
> > +        close(fd);
> > +
> > +        return 0;
> > +   }
> > +
> > +2.0 Mouse movements
> > +-------------------
> > +
> > +This example shows how to create a virtual device that behaves like a physical
> > +mouse.
> > +
> > +.. code-block:: c
> > +
> > +    #include <linux/uinput.h>
> > +
> > +    /* emit function is identical to of the first example */
> > +
> > +    struct uinput_setup usetup;
> > +    int i = 50;
> > +
> > +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > +
> > +    /* enable mouse button left and relative events */
> > +    ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > +    ioctl(fd, UI_SET_KEYBIT, BTN_LEFT);
> > +
> > +    ioctl(fd, UI_SET_EVBIT, EV_REL);
> > +    ioctl(fd, UI_SET_RELBIT, REL_X);
> > +    ioctl(fd, UI_SET_RELBIT, REL_Y);
> > +
> > +    memset(&usetup, 0, sizeof(usetup));
> > +    usetup.id.bustype = BUS_USB;
> > +    usetup.id.vendor = 0x1234; /* sample vendor */
> > +    strcpy(usetup.name, "Example device");
> > +
> > +    ioctl(fd, UI_DEV_SETUP, &usetup);
> > +    ioctl(fd, UI_DEV_CREATE);
> > +
> > +    /* UI_DEV_CREATE causes the kernel to create 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
> > +     **/
> > +
> > +    /* moves the mouse diagonally, 5 units per axis */
> > +    while (i--) {
> > +        emit(EV_REL, REL_X, 5);
> > +        emit(EV_REL, REL_Y, 5);
> > +        emit(EV_SYN, SYN_REPORT, 0);
> > +        usleep(15000);
> > +    }
> > +
> > +    ioctl(fd, UI_DEV_DESTROY);
> > +    close(fd);
> > +
> > +    return 0;
> > +
> > +3.0 uinput old interface
> > +------------------------
> > +
> > +Before kernel 4.5, uinput didn't have an ioctl to setup a virtual device. When
> > +running a version prior to 4.5, the user needs to fill a different struct and
> > +call write on the uinput file descriptor.
> 
> I think this should really include the version check.

Uhg, I forgot this one again. Fixed here.

Sending a new version soon.

> 
> Cheers,
>    Peter
> 
> > +
> > +.. code-block:: c
> > +
> > +    #include <linux/uinput.h>
> > +
> > +    /* emit function is identical to of the first example */
> > +
> > +    struct uinput_user_dev uud;
> > +
> > +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > +
> > +    /* 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);
> > +
> > +    /* UI_DEV_CREATE causes the kernel to create 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
> > +     **/
> > +
> > +    /* 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

Re: [PATCH v2] Documentation: Input: Add uinput documentation

[Peter Hutterer]

On Sun, Mar 26, 2017 at 01:21:14PM -0300, Marcos Paulo de Souza wrote:
> On Fri, Mar 24, 2017 at 02:39:13PM +1000, Peter Hutterer wrote:
> > as usual, reading through these things multiple times means one spots a
> > couple of different things. sorry about that.
> > 
> > On Fri, Mar 24, 2017 at 12:34:59AM -0300, Marcos Paulo de Souza wrote:
> > > Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> > > ---
> > >  Documentation/input/uinput.rst | 196 +++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 196 insertions(+)
> > >  create mode 100644 Documentation/input/uinput.rst
> > > 
> > > diff --git a/Documentation/input/uinput.rst b/Documentation/input/uinput.rst
> > > new file mode 100644
> > > index 0000000..eb79b77
> > > --- /dev/null
> > > +++ b/Documentation/input/uinput.rst
> > > @@ -0,0 +1,196 @@
> > > +=============
> > > +uinput module
> > > +=============
> > > +
> > > +Introduction
> > > +============
> > > +
> > > +uinput is a kernel module that makes possible to create and handle input devices
> > 
> > typo: makes *it* possible.
> > 
> > replace "to create and handle" with "to emulate", the rest is in the next
> > sentence anyway
> 
> Fixed.
> 
> > 
> > > +from userspace. By writing to the module's /dev/uinput (or /dev/input/uinput), a
> > > +process can create a virtual device with specific capabilities.
> > > +Once created, the process can send events through that virtual device.
> > > +
> > > +Interface
> > > +=========
> > > +
> > > +::
> > > +
> > > +  linux/uinput.h
> > > +
> > > +The uinput header defines ioctls to create, setup and destroy virtual devices.
> > > +
> > > +libevdev
> > > +========
> > > +
> > > +libevdev is a wrapper library for evdev devices, making uinput setup easier
> > > +by skipping a lot of ioctl calls. When dealing with uinput, libevdev is the best
> > > +alternative over accessing uinput directly, and it is less error prone.
> > 
> > "libevdev is a wrapper library for evdev devices that provides interfaces to
> > create uinput devices and send events. libevdev is less error-prone than
> > accessing uinput directly and should be considered for new software".
> 
> Much better. Fixed.
> 
> > 
> > > +
> > > +For examples and more information about libevdev:
> > > +https://cgit.freedesktop.org/libevdev
> > > +
> > 
> > Please use https://www.freedesktop.org/software/libevdev/doc/latest/
> > (which needs a link to the git repo, I'll fix that in a minute)
> 
> Fixed.
> 
> > 
> > > +Examples
> > > +========
> > > +
> > > +1.0 Keyboard events
> > > +-------------------
> > > +
> > > +This first example shows how to create a new virtual device and how to send a
> > > +key event. All default imports and error handlers were removed for the sake of
> > > +simplicity.
> > > +
> > > +.. code-block:: c
> > > +
> > > +   #include <linux/uinput.h>
> > > +
> > > +   int fd;
> > > +
> > > +   void emit(int type, int code, int val)
> > > +   {
> > > +        struct input_event ie;
> > > +
> > > +        ie.type = type;
> > > +        ie.code = code;
> > > +        ie.value = val;
> > > +        /* below timestamp values are ignored */
> > > +        ie.time.tv_sec = 0;
> > > +        ie.time.tv_usec = 0;
> > > +
> > > +        write(fd, &ie, sizeof(ie));
> > > +   }
> > > +
> > > +   int main() {
> > > +        struct uinput_setup usetup;
> > > +
> > > +        fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > > +
> > > +        /* the ioctls below enables the to be created device to key
> > > +         * events, in this case the space key
> > > +         **/
> > 
> > the comment terminator doesn't look right
> 
> Fixed.
> 
> > 
> > > +        ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > > +        ioctl(fd, UI_SET_KEYBIT, KEY_SPACE);
> > > +
> > > +        memset(&usetup, 0, sizeof(usetup));
> > > +        usetup.id.bustype = BUS_USB;
> > > +        usetup.id.vendor = 0x1234; /* sample vendor */
> > 
> > add a sample product id too please
> Added.
> 
> > 
> > > +        strcpy(usetup.name, "Example device");
> > > +
> > > +        ioctl(fd, UI_DEV_SETUP, &usetup);
> > > +        ioctl(fd, UI_DEV_CREATE);
> > > +
> > > +        /* UI_DEV_CREATE causes the kernel to create the device nodes for this
> > 
> > "On UI_DEV_CREATE the kernel creates the device nodes..."
> Fixed.
> 
> > 
> > > +         * 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
> > > +         **/
> > 
> > the comment terminator doesn't look right
> > 
> > note: the actual pause is missing now :)
> 
> I thought you wanted just the warning, but ok, I added back the sleep
> call :)

better to have something that can be copy-pasted and works than expecting
people to add misc bits.

> > > +
> > > +        /* 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);
> > 
> > come to think of it, you probably need a pause here too, iirc a caller may
> > get ENODEV before reading the key events otherwise.
> 
> We need a sleep call after each emitted event?

no, I think we need a sleep between the final emit and the
UI_DEV_DESTROY, otherwise those events may not get delivered (not 100%
sure).

Cheers,
   Peter

> 
> > 
> > > +
> > > +        ioctl(fd, UI_DEV_DESTROY);
> > > +        close(fd);
> > > +
> > > +        return 0;
> > > +   }
> > > +
> > > +2.0 Mouse movements
> > > +-------------------
> > > +
> > > +This example shows how to create a virtual device that behaves like a physical
> > > +mouse.
> > > +
> > > +.. code-block:: c
> > > +
> > > +    #include <linux/uinput.h>
> > > +
> > > +    /* emit function is identical to of the first example */
> > > +
> > > +    struct uinput_setup usetup;
> > > +    int i = 50;
> > > +
> > > +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > > +
> > > +    /* enable mouse button left and relative events */
> > > +    ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > > +    ioctl(fd, UI_SET_KEYBIT, BTN_LEFT);
> > > +
> > > +    ioctl(fd, UI_SET_EVBIT, EV_REL);
> > > +    ioctl(fd, UI_SET_RELBIT, REL_X);
> > > +    ioctl(fd, UI_SET_RELBIT, REL_Y);
> > > +
> > > +    memset(&usetup, 0, sizeof(usetup));
> > > +    usetup.id.bustype = BUS_USB;
> > > +    usetup.id.vendor = 0x1234; /* sample vendor */
> > > +    strcpy(usetup.name, "Example device");
> > > +
> > > +    ioctl(fd, UI_DEV_SETUP, &usetup);
> > > +    ioctl(fd, UI_DEV_CREATE);
> > > +
> > > +    /* UI_DEV_CREATE causes the kernel to create 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
> > > +     **/
> > > +
> > > +    /* moves the mouse diagonally, 5 units per axis */
> > > +    while (i--) {
> > > +        emit(EV_REL, REL_X, 5);
> > > +        emit(EV_REL, REL_Y, 5);
> > > +        emit(EV_SYN, SYN_REPORT, 0);
> > > +        usleep(15000);
> > > +    }
> > > +
> > > +    ioctl(fd, UI_DEV_DESTROY);
> > > +    close(fd);
> > > +
> > > +    return 0;
> > > +
> > > +3.0 uinput old interface
> > > +------------------------
> > > +
> > > +Before kernel 4.5, uinput didn't have an ioctl to setup a virtual device. When
> > > +running a version prior to 4.5, the user needs to fill a different struct and
> > > +call write on the uinput file descriptor.
> > 
> > I think this should really include the version check.
> 
> Uhg, I forgot this one again. Fixed here.
> 
> Sending a new version soon.
> 
> > 
> > Cheers,
> >    Peter
> > 
> > > +
> > > +.. code-block:: c
> > > +
> > > +    #include <linux/uinput.h>
> > > +
> > > +    /* emit function is identical to of the first example */
> > > +
> > > +    struct uinput_user_dev uud;
> > > +
> > > +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > > +
> > > +    /* 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);
> > > +
> > > +    /* UI_DEV_CREATE causes the kernel to create 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
> > > +     **/
> > > +
> > > +    /* 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

Re: [PATCH v2] Documentation: Input: Add uinput documentation

[Marcos Paulo de Souza]

On Mon, Mar 27, 2017 at 08:52:58AM +1000, Peter Hutterer wrote:
> On Sun, Mar 26, 2017 at 01:21:14PM -0300, Marcos Paulo de Souza wrote:
> > On Fri, Mar 24, 2017 at 02:39:13PM +1000, Peter Hutterer wrote:
> > > as usual, reading through these things multiple times means one spots a
> > > couple of different things. sorry about that.
> > > 
> > > On Fri, Mar 24, 2017 at 12:34:59AM -0300, Marcos Paulo de Souza wrote:
> > > > Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> > > > ---
> > > >  Documentation/input/uinput.rst | 196 +++++++++++++++++++++++++++++++++++++++++
> > > >  1 file changed, 196 insertions(+)
> > > >  create mode 100644 Documentation/input/uinput.rst
> > > > 
> > > > diff --git a/Documentation/input/uinput.rst b/Documentation/input/uinput.rst
> > > > new file mode 100644
> > > > index 0000000..eb79b77
> > > > --- /dev/null
> > > > +++ b/Documentation/input/uinput.rst
> > > > @@ -0,0 +1,196 @@
> > > > +=============
> > > > +uinput module
> > > > +=============
> > > > +
> > > > +Introduction
> > > > +============
> > > > +
> > > > +uinput is a kernel module that makes possible to create and handle input devices
> > > 
> > > typo: makes *it* possible.
> > > 
> > > replace "to create and handle" with "to emulate", the rest is in the next
> > > sentence anyway
> > 
> > Fixed.
> > 
> > > 
> > > > +from userspace. By writing to the module's /dev/uinput (or /dev/input/uinput), a
> > > > +process can create a virtual device with specific capabilities.
> > > > +Once created, the process can send events through that virtual device.
> > > > +
> > > > +Interface
> > > > +=========
> > > > +
> > > > +::
> > > > +
> > > > +  linux/uinput.h
> > > > +
> > > > +The uinput header defines ioctls to create, setup and destroy virtual devices.
> > > > +
> > > > +libevdev
> > > > +========
> > > > +
> > > > +libevdev is a wrapper library for evdev devices, making uinput setup easier
> > > > +by skipping a lot of ioctl calls. When dealing with uinput, libevdev is the best
> > > > +alternative over accessing uinput directly, and it is less error prone.
> > > 
> > > "libevdev is a wrapper library for evdev devices that provides interfaces to
> > > create uinput devices and send events. libevdev is less error-prone than
> > > accessing uinput directly and should be considered for new software".
> > 
> > Much better. Fixed.
> > 
> > > 
> > > > +
> > > > +For examples and more information about libevdev:
> > > > +https://cgit.freedesktop.org/libevdev
> > > > +
> > > 
> > > Please use https://www.freedesktop.org/software/libevdev/doc/latest/
> > > (which needs a link to the git repo, I'll fix that in a minute)
> > 
> > Fixed.
> > 
> > > 
> > > > +Examples
> > > > +========
> > > > +
> > > > +1.0 Keyboard events
> > > > +-------------------
> > > > +
> > > > +This first example shows how to create a new virtual device and how to send a
> > > > +key event. All default imports and error handlers were removed for the sake of
> > > > +simplicity.
> > > > +
> > > > +.. code-block:: c
> > > > +
> > > > +   #include <linux/uinput.h>
> > > > +
> > > > +   int fd;
> > > > +
> > > > +   void emit(int type, int code, int val)
> > > > +   {
> > > > +        struct input_event ie;
> > > > +
> > > > +        ie.type = type;
> > > > +        ie.code = code;
> > > > +        ie.value = val;
> > > > +        /* below timestamp values are ignored */
> > > > +        ie.time.tv_sec = 0;
> > > > +        ie.time.tv_usec = 0;
> > > > +
> > > > +        write(fd, &ie, sizeof(ie));
> > > > +   }
> > > > +
> > > > +   int main() {
> > > > +        struct uinput_setup usetup;
> > > > +
> > > > +        fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > > > +
> > > > +        /* the ioctls below enables the to be created device to key
> > > > +         * events, in this case the space key
> > > > +         **/
> > > 
> > > the comment terminator doesn't look right
> > 
> > Fixed.
> > 
> > > 
> > > > +        ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > > > +        ioctl(fd, UI_SET_KEYBIT, KEY_SPACE);
> > > > +
> > > > +        memset(&usetup, 0, sizeof(usetup));
> > > > +        usetup.id.bustype = BUS_USB;
> > > > +        usetup.id.vendor = 0x1234; /* sample vendor */
> > > 
> > > add a sample product id too please
> > Added.
> > 
> > > 
> > > > +        strcpy(usetup.name, "Example device");
> > > > +
> > > > +        ioctl(fd, UI_DEV_SETUP, &usetup);
> > > > +        ioctl(fd, UI_DEV_CREATE);
> > > > +
> > > > +        /* UI_DEV_CREATE causes the kernel to create the device nodes for this
> > > 
> > > "On UI_DEV_CREATE the kernel creates the device nodes..."
> > Fixed.
> > 
> > > 
> > > > +         * 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
> > > > +         **/
> > > 
> > > the comment terminator doesn't look right
> > > 
> > > note: the actual pause is missing now :)
> > 
> > I thought you wanted just the warning, but ok, I added back the sleep
> > call :)
> 
> better to have something that can be copy-pasted and works than expecting
> people to add misc bits.

Absolutely.

> 
> > > > +
> > > > +        /* 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);
> > > 
> > > come to think of it, you probably need a pause here too, iirc a caller may
> > > get ENODEV before reading the key events otherwise.
> > 
> > We need a sleep call after each emitted event?
> 
> no, I think we need a sleep between the final emit and the
> UI_DEV_DESTROY, otherwise those events may not get delivered (not 100%
> sure).

I can add another comment and another sleep call, if this helps. Adding then in the next submission.

> 
> Cheers,
>    Peter
> 
> > 
> > > 
> > > > +
> > > > +        ioctl(fd, UI_DEV_DESTROY);
> > > > +        close(fd);
> > > > +
> > > > +        return 0;
> > > > +   }
> > > > +
> > > > +2.0 Mouse movements
> > > > +-------------------
> > > > +
> > > > +This example shows how to create a virtual device that behaves like a physical
> > > > +mouse.
> > > > +
> > > > +.. code-block:: c
> > > > +
> > > > +    #include <linux/uinput.h>
> > > > +
> > > > +    /* emit function is identical to of the first example */
> > > > +
> > > > +    struct uinput_setup usetup;
> > > > +    int i = 50;
> > > > +
> > > > +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > > > +
> > > > +    /* enable mouse button left and relative events */
> > > > +    ioctl(fd, UI_SET_EVBIT, EV_KEY);
> > > > +    ioctl(fd, UI_SET_KEYBIT, BTN_LEFT);
> > > > +
> > > > +    ioctl(fd, UI_SET_EVBIT, EV_REL);
> > > > +    ioctl(fd, UI_SET_RELBIT, REL_X);
> > > > +    ioctl(fd, UI_SET_RELBIT, REL_Y);
> > > > +
> > > > +    memset(&usetup, 0, sizeof(usetup));
> > > > +    usetup.id.bustype = BUS_USB;
> > > > +    usetup.id.vendor = 0x1234; /* sample vendor */
> > > > +    strcpy(usetup.name, "Example device");
> > > > +
> > > > +    ioctl(fd, UI_DEV_SETUP, &usetup);
> > > > +    ioctl(fd, UI_DEV_CREATE);
> > > > +
> > > > +    /* UI_DEV_CREATE causes the kernel to create 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
> > > > +     **/
> > > > +
> > > > +    /* moves the mouse diagonally, 5 units per axis */
> > > > +    while (i--) {
> > > > +        emit(EV_REL, REL_X, 5);
> > > > +        emit(EV_REL, REL_Y, 5);
> > > > +        emit(EV_SYN, SYN_REPORT, 0);
> > > > +        usleep(15000);
> > > > +    }
> > > > +
> > > > +    ioctl(fd, UI_DEV_DESTROY);
> > > > +    close(fd);
> > > > +
> > > > +    return 0;
> > > > +
> > > > +3.0 uinput old interface
> > > > +------------------------
> > > > +
> > > > +Before kernel 4.5, uinput didn't have an ioctl to setup a virtual device. When
> > > > +running a version prior to 4.5, the user needs to fill a different struct and
> > > > +call write on the uinput file descriptor.
> > > 
> > > I think this should really include the version check.
> > 
> > Uhg, I forgot this one again. Fixed here.
> > 
> > Sending a new version soon.
> > 
> > > 
> > > Cheers,
> > >    Peter
> > > 
> > > > +
> > > > +.. code-block:: c
> > > > +
> > > > +    #include <linux/uinput.h>
> > > > +
> > > > +    /* emit function is identical to of the first example */
> > > > +
> > > > +    struct uinput_user_dev uud;
> > > > +
> > > > +    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
> > > > +
> > > > +    /* 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);
> > > > +
> > > > +    /* UI_DEV_CREATE causes the kernel to create 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
> > > > +     **/
> > > > +
> > > > +    /* 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

-- 
Thanks,
	Marcos