keyboard: add haptic feedback

shared/force_feedback.c

@@ -0,0 +1,109 @@
+/**
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "force_feedback.h"
+
+#include "log.h"
+
+#include <linux/input.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <libudev.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#define bit_is_set(array, bit)  ((array[bit / 8] >> bit % 8) & 0x01)
+
+/**
+ * Static variables
+ */
+
+static int fd = -1;
+static struct input_event ff_event = {
+    .type = EV_FF,
+    .code = 0,
+    .value = 1
+};
+
+/**
+ * Public functions
+ */
+
+void bbx_force_feedback_connect(struct udev_device* device) {
+    if (fd >= 0)
+        return;
+
+    const char* node = udev_device_get_devnode(device);
+
+    int fd_event = open(node, O_RDWR);
+    if (fd_event < 0) {
+        bbx_log(BBX_LOG_LEVEL_ERROR, "Can't open %s", node);
+        return;
+    }
+
+    int n_effects;
+    if (ioctl(fd_event, EVIOCGEFFECTS, &n_effects) == -1 || n_effects == 0) {
+        close(fd_event);
+        return;
+    }
+
+    bbx_log(BBX_LOG_LEVEL_VERBOSE, "Found a force feedback device: %s", node);
+
+    uint8_t features[(FF_CNT + 7) / 8];
+    if (ioctl(fd_event, EVIOCGBIT(EV_FF, sizeof(features)), features) == -1) {
+        bbx_log(BBX_LOG_LEVEL_ERROR, "Can't request features of %s", node);
+        close(fd_event);
+        return;
+    }
+
+    if (!bit_is_set(features, FF_RUMBLE)) {
+        bbx_log(BBX_LOG_LEVEL_VERBOSE, "%s does not support FF_RUMBLE", node);
+        close(fd_event);
+        return;
+    }
+
+    struct ff_effect effect = {
+        .type = FF_RUMBLE,
+	.id = -1,
+	.direction = 0x0000,
+	.trigger.button = 0,
+	.trigger.interval = 0,
+	.replay.length = 50,
+	.replay.delay = 0,
+	.u.rumble.strong_magnitude = 0xC000,
+	.u.rumble.weak_magnitude = 0xC000
+    };
+
+    if (ioctl(fd_event, EVIOCSFF, &effect) == -1) {
+        bbx_log(BBX_LOG_LEVEL_ERROR, "Can't upload the effect");
+        close(fd_event);
+        return;
+    }
+
+    ff_event.code = effect.id;
+
+    if (bit_is_set(features, FF_GAIN)) {
+        struct input_event gain = {
+            .type = EV_FF,
+            .code = FF_GAIN,
+            .value = 0xFFFF
+        };
+
+        if (write(fd_event, &gain, sizeof(gain)) != sizeof(gain))
+            bbx_log(BBX_LOG_LEVEL_WARNING, "Can't set the gain");
+    }
+
+    fd = fd_event;
+}
+
+void bbx_force_feedback_play() {
+    if (fd < 0)
+        return;
+
+    if (write(fd, &ff_event, sizeof(ff_event)) != sizeof(ff_event)) {
+        // Assume that the force feedback device was disconnected
+        close(fd);
+        fd = -1;
+    }
+}

shared/force_feedback.h

@@ -0,0 +1,20 @@
+/**
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#ifndef BBX_FORCE_FEEDBACK_H
+#define BBX_FORCE_FEEDBACK_H
+
+#include <libudev.h>
+
+/**
+ * Try to connect a force feedback device.
+ */
+void bbx_force_feedback_connect(struct udev_device* device);
+
+/**
+ * Play a force feedback effect.
+ */
+void bbx_force_feedback_play();
+
+#endif /* BBX_FORCE_FEEDBACK_H */

shared/indev.c

@@ -6,6 +6,7 @@
 #include "indev.h"
 
 #include "cursor/cursor.h"
+#include "force_feedback.h"
 #include "log.h"
 
 #include "lvgl/lvgl.h"
@@ -93,6 +94,7 @@ static struct {
 #endif
     uint8_t pointer : 1;
     uint8_t touchscreen : 1;
+    uint8_t force_feedback : 1;
 } options;
 
 /**
@@ -641,6 +643,12 @@ static void attach_input_device(struct udev_device* device) {
         break;
     }
 
+    /* A device can be a force feedback device and an input device independently,
+       so we check for both capabilities. */
+
+    if (options.force_feedback)
+        bbx_force_feedback_connect(device);
+
     struct libinput_device* dev = libinput_path_add_device(context_libinput, node);
     if (!dev) {
         bbx_log(BBX_LOG_LEVEL_WARNING, "libinput can't use %s", node);
@@ -795,6 +803,7 @@ uint8_t bbx_indev_init(int fd_epoll, const struct bbx_indev_opts* opts) {
 #endif
     options.pointer = opts->pointer;
     options.touchscreen = opts->touchscreen;
+    options.force_feedback = opts->force_feedback;
 
     attach_input_devices();
 

shared/indev.h

@@ -20,6 +20,7 @@ struct bbx_indev_opts {
 #endif
     uint8_t pointer : 1;
     uint8_t touchscreen : 1;
+    uint8_t force_feedback : 1;
 };
 
 #ifndef BBX_APP_BUFFYBOARD