From 45c6265b4504396f625105cf52b2e97b3e843777 Mon Sep 17 00:00:00 2001
From: Vitalii Popov <symbx.live@gmail.com>
Date: Wed, 14 Oct 2026 22:58:53 +0300
Subject: [PATCH] add ability to work with constant-only driver

---
 src/fbd-dev-vibra.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/fbd-dev-vibra.c b/src/fbd-dev-vibra.c
index f764a6c..c43b0a5 100644
--- a/src/fbd-dev-vibra.c
+++ b/src/fbd-dev-vibra.c
@@ -48,6 +48,9 @@ typedef struct _FbdDevVibra {
   GUdevDevice *device;
   gint fd;
   gint id; /* currently used id */
+  /* The driver advertises rumble or periodic effects but rejects them (Qualcomm qti-haptics) */
+  gboolean constant_only;
+  gboolean has_constant;
 
   FbdDevVibraFeatureFlags features;
 } FbdDevVibra;
@@ -142,6 +145,8 @@ initable_init (GInitable     *initable,
     return FALSE;
   }
 
+  self->has_constant = HAS_FEATURE (FF_CONSTANT, features);
+
   /* Set gain to 75% if supported */
   if (HAS_FEATURE(FF_GAIN, features)) {
     self->features |= FBD_DEV_VIBRA_FEATURE_GAIN;
@@ -232,6 +237,30 @@ fbd_dev_vibra_new (GUdevDevice *device, GError **error)
                                         NULL));
 }
 
+static gboolean
+upload_effect (FbdDevVibra *self, struct ff_effect *effect, double magnitude)
+{
+  struct ff_effect constant = { 0 };
+
+  if (!self->constant_only) {
+    if (ioctl (self->fd, EVIOCSFF, effect) != -1)
+      return TRUE;
+    if (errno != EINVAL || !self->has_constant)
+      return FALSE;
+    g_debug ("Effect type %u rejected, using constant effects", effect->type);
+    self->constant_only = TRUE;
+  }
+
+  constant.type = FF_CONSTANT;
+  constant.id = -1;
+  constant.u.constant.level = 0x7FFF * magnitude;
+  constant.replay = effect->replay;
+  if (ioctl (self->fd, EVIOCSFF, &constant) == -1)
+    return FALSE;
+  effect->id = constant.id;
+  return TRUE;
+}
+
 gboolean
 fbd_dev_vibra_rumble (FbdDevVibra *self, double magnitude, guint duration, gboolean upload)
 {
@@ -250,7 +279,7 @@ fbd_dev_vibra_rumble (FbdDevVibra *self, double magnitude, guint duration, gbool
 
   if (upload) {
     g_debug("Uploading rumbling vibra effect (%d)", self->fd);
-    if (ioctl(self->fd, EVIOCSFF, &effect) == -1) {
+    if (!upload_effect (self, &effect, magnitude)) {
       g_warning ("Failed to upload rumbling vibra effect: %s", g_strerror (errno));
       return FALSE;
     }
@@ -301,7 +330,7 @@ fbd_dev_vibra_periodic (FbdDevVibra *self,
   effect.replay.delay = 200;
 
   g_debug("Uploading periodic effect (%d)", self->fd);
-  if (ioctl(self->fd, EVIOCSFF, &effect) == -1) {
+  if (!upload_effect (self, &effect, magnitude)) {
     g_warning ("Failed to upload periodic vibra effect: %s", g_strerror (errno));
     return FALSE;
   }