[PATCH] drm/amdgpu: fix build for CONFIG_DRM_FBDEV_EMULATION=n

[Yury Norov <ynorov@nvidia.com>]

The merge-commit 02e778f12359 ("Merge tag 'amd-drm-next-7.1-2026-03-12' of
https://gitlab.freedesktop.org/agd5f/linux into drm-next") removes stubs
for drm_fb_helper_xxx() functions, so the buld gets broken if
DRM_FBDEV_EMULATION is not set.

‘drm_fb_helper_gem_is_fb’; did you mean ‘drm_fb_helper_from_client’? [-Wimplicit-function-declaration]
 1777 |                 if (!drm_fb_helper_gem_is_fb(dev->fb_helper, fb->obj[0])) {
      |                      ^~~~~~~~~~~~~~~~~~~~~~~
      |                      drm_fb_helper_from_client

Restore the stubs.
Fixes: 02e778f12359 ("Merge tag 'amd-drm-next-7.1-2026-03-12' of https://gitlab.freedesktop.org/agd5f/linux into drm-next")
Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 include/drm/drm_fb_helper.h | 111 ++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)

diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index bf391903443d..ca214b5c0283 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -273,6 +273,117 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper);
 int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper);
 bool drm_fb_helper_gem_is_fb(const struct drm_fb_helper *fb_helper,
 			     const struct drm_gem_object *obj);
+#else
+static inline bool drm_fb_helper_gem_is_fb(const struct drm_fb_helper *fb_helper,
+					   const struct drm_gem_object *obj)
+{
+	return false;
+}
+
+static inline void drm_fb_helper_prepare(struct drm_device *dev,
+					 struct drm_fb_helper *helper,
+					 unsigned int preferred_bpp,
+					 const struct drm_fb_helper_funcs *funcs)
+{
+}
+
+static inline void drm_fb_helper_unprepare(struct drm_fb_helper *fb_helper)
+{
+}
+
+static inline int drm_fb_helper_init(struct drm_device *dev,
+		       struct drm_fb_helper *helper)
+{
+	/* So drivers can use it to free the struct */
+	helper->dev = dev;
+	dev->fb_helper = helper;
+
+	return 0;
+}
+
+static inline void drm_fb_helper_fini(struct drm_fb_helper *helper)
+{
+	if (helper && helper->dev)
+		helper->dev->fb_helper = NULL;
+}
+
+static inline int drm_fb_helper_blank(int blank, struct fb_info *info)
+{
+	return 0;
+}
+
+static inline int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
+					    struct fb_info *info)
+{
+	return 0;
+}
+
+static inline int drm_fb_helper_set_par(struct fb_info *info)
+{
+	return 0;
+}
+
+static inline int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
+					  struct fb_info *info)
+{
+	return 0;
+}
+
+static inline int
+drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
+{
+	return 0;
+}
+
+static inline void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper)
+{
+}
+
+static inline void
+drm_fb_helper_fill_info(struct fb_info *info,
+			struct drm_fb_helper *fb_helper,
+			struct drm_fb_helper_surface_size *sizes)
+{
+}
+
+static inline int drm_fb_helper_setcmap(struct fb_cmap *cmap,
+					struct fb_info *info)
+{
+	return 0;
+}
+
+static inline int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
+				      unsigned long arg)
+{
+	return 0;
+}
+
+#ifdef CONFIG_FB_DEFERRED_IO
+static inline void drm_fb_helper_deferred_io(struct fb_info *info,
+					     struct list_head *pagelist)
+{
+}
+#endif
+
+static inline void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper,
+					     bool suspend)
+{
+}
+
+static inline void
+drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper, bool suspend)
+{
+}
+
+static inline int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
+{
+	return 0;
+}
+
+static inline int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper)
+{
+	return 0;
+}
 #endif
 
 #endif
-- 
2.51.0