xfree86: add null input driver

This is a dummy driver adding a core keyboard and core mouse pointer
device, who behave like normal drivers but never sending any events.

Meant for special cases where no actual input devices are connected,
but shall look like there were some.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

hw/xfree86/drivers/input/meson.build

@@ -1,3 +1,7 @@
 if get_option('xf86-input-inputtest')
     subdir('inputtest')
 endif
+
+if get_option('xf86-input-null')
+    subdir('null')
+endif

hw/xfree86/drivers/input/null/meson.build

@@ -0,0 +1,18 @@
+nullinputdrv_srcs = [
+    'null.c',
+]
+
+shared_module(
+    'nullinput_drv',
+    nullinputdrv_srcs,
+    name_prefix: '',
+
+    include_directories: [inc, xorg_inc],
+    c_args: xorg_c_args,
+    dependencies: [common_dep],
+
+    install: true,
+    install_dir: join_paths(module_abi_dir, 'input'),
+
+    link_with: xserver_exec,
+)

hw/xfree86/drivers/input/null/null.c

@@ -0,0 +1,103 @@
+#include <xorg-config.h>
+
+#include <exevents.h>
+#include <xserver-properties.h>
+
+#include <xorgVersion.h>
+#include <xf86Xinput.h>
+
+/* dummy needed, so that clients don't get BadValue error
+   when trying to ring the bell. */
+static void nullinput_bell(int percent, DeviceIntPtr pDev, void *ctrl, int unused) { }
+
+/* dummy needed, because no NULL protection here yet */
+static void nullinput_keyctrl(DeviceIntPtr pDev, KeybdCtrl *ctrl) { }
+
+/* dummy needed, because no NULL protection here yet */
+static void nullinput_pointer(DeviceIntPtr dev, PtrCtrl *ctrl) { }
+
+static int nullinput_device_init(DeviceIntPtr dev)
+{
+    Atom axes_labels[2] = {
+        XIGetKnownProperty(AXIS_LABEL_PROP_ABS_X),
+        XIGetKnownProperty(AXIS_LABEL_PROP_ABS_Y)
+    };
+
+    Atom btn_labels[3] = {
+        XIGetKnownProperty(BTN_LABEL_PROP_BTN_LEFT),
+        XIGetKnownProperty(BTN_LABEL_PROP_BTN_MIDDLE),
+        XIGetKnownProperty(BTN_LABEL_PROP_BTN_RIGHT)
+    };
+
+    unsigned char map[4] = { 0, 1, 2, 3 };
+
+    dev->public.on = FALSE;
+
+    if (!InitButtonClassDeviceStruct(dev, sizeof(map)-1, btn_labels, map))
+        return !Success;
+
+    if (InitKeyboardDeviceStruct(dev, NULL, nullinput_bell, nullinput_keyctrl))
+        return !Success;
+
+    if (!InitValuatorClassDeviceStruct(dev, 2, axes_labels, 0, Absolute))
+        return !Success;
+
+    if (!InitPtrFeedbackClassDeviceStruct(dev, nullinput_pointer))
+        return !Success;
+
+    return Success;
+}
+
+static int nullinput_device_control(DeviceIntPtr dev, int what)
+{
+    switch (what)
+    {
+        case DEVICE_INIT:
+            return nullinput_device_init(dev);
+
+        case DEVICE_ON:
+            dev->public.on = TRUE;
+            return Success;
+
+        case DEVICE_OFF:
+        case DEVICE_CLOSE:
+            dev->public.on = FALSE;
+            return Success;
+    }
+    return BadValue;
+}
+
+static int nullinput_preinit(InputDriverPtr drv, InputInfoPtr pInfo, int flags)
+{
+    pInfo->type_name = "null";
+    pInfo->device_control = nullinput_device_control;
+    pInfo->fd = -1;
+    return Success;
+}
+
+static void nullinput_uninit(InputDriverPtr drv,InputInfoPtr pInfo, int flags)
+{
+    pInfo->dev->public.on = FALSE;
+}
+
+InputDriverRec NullInput = {
+    .driverVersion = 1,
+    .driverName    = "null",
+    .PreInit       = nullinput_preinit,
+    .UnInit        = nullinput_uninit,
+};
+
+static void* nullinput_setup(void *mod, void *opt, int *errmaj, int *errmin)
+{
+    xf86AddInputDriver(&NullInput, mod, 0);
+    return mod;
+}
+
+XF86_MODULE_DATA_INPUT(
+    nullinput,
+    nullinput_setup,
+    NULL,
+    "nullinput",
+    XORG_VERSION_MAJOR,
+    XORG_VERSION_MINOR,
+    XORG_VERSION_PATCH);

meson_options.txt

@@ -158,6 +158,8 @@ option('docs-pdf', type: 'combo', choices: ['true', 'false', 'auto'], value: 'au
 # optional xfree86 DDX drivers
 option('xf86-input-inputtest', type: 'boolean', value: true,
        description: 'Test input driver support on XLibre')
+option('xf86-input-null', type: 'boolean', value: true,
+       description: 'Null input driver')
 
 # legacy nvidia driver quirks
 option('legacy_nvidia_padding', type: 'boolean', value: false,