video/fb: Add fb_register_device

so the user could register fb device directly instead
go through the sequence of up_fbinitialize/up_fbgetvplane

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

drivers/video/fb.c

@@ -1386,7 +1386,7 @@ int fb_paninfo_count(FAR struct fb_vtable_s *vtable, int overlay)
 }
 
 /****************************************************************************
- * Name: fb_register
+ * Name: fb_register_device
  *
  * Description:
  *   Register the framebuffer character device at /dev/fbN where N is the
@@ -1401,6 +1401,7 @@ int fb_paninfo_count(FAR struct fb_vtable_s *vtable, int overlay)
  *             layers (each layer is consider a display).  Typically zero.
  *   plane   - Identifies the color plane on hardware that supports separate
  *             framebuffer "planes" for each color component.
+ *   vtable  - Pointer to framebuffer's virtual table.
  *
  * Returned Value:
  *   Zero (OK) is returned success; a negated errno value is returned on any
@@ -1408,7 +1409,8 @@ int fb_paninfo_count(FAR struct fb_vtable_s *vtable, int overlay)
  *
  ****************************************************************************/
 
-int fb_register(int display, int plane)
+int fb_register_device(int display, int plane,
+                       FAR struct fb_vtable_s *vtable)
 {
   FAR struct fb_chardev_s *fb;
   struct fb_panelinfo_s panelinfo;
@@ -1426,30 +1428,15 @@ int fb_register(int display, int plane)
       return -ENOMEM;
     }
 
-  /* Initialize the frame buffer device. */
-
-  ret = up_fbinitialize(display);
-  if (ret < 0)
-    {
-      gerr("ERROR: up_fbinitialize() failed for display %d: %d\n",
-           display, ret);
-      goto errout_with_fb;
-    }
-
   DEBUGASSERT((unsigned)plane <= UINT8_MAX);
+  DEBUGASSERT(vtable != NULL);
   fb->plane  = plane;
-
+  fb->vtable = vtable;
-  fb->vtable = up_fbgetvplane(display, plane);
-  if (fb->vtable == NULL)
-    {
-      gerr("ERROR: up_fbgetvplane() failed, vplane=%d\n", plane);
-      goto errout_with_fb;
-    }
 
   /* Initialize the frame buffer instance. */
 
-  DEBUGASSERT(fb->vtable->getvideoinfo != NULL);
+  DEBUGASSERT(vtable->getvideoinfo != NULL);
-  ret = fb->vtable->getvideoinfo(fb->vtable, &vinfo);
+  ret = vtable->getvideoinfo(vtable, &vinfo);
   if (ret < 0)
     {
       gerr("ERROR: getvideoinfo() failed: %d\n", ret);
@@ -1505,15 +1492,14 @@ int fb_register(int display, int plane)
 
   nxmutex_init(&fb->lock);
 
-  ret = register_driver(devname, &g_fb_fops, 0666, (FAR void *)fb);
+  ret = register_driver(devname, &g_fb_fops, 0666, fb);
   if (ret < 0)
     {
       gerr("ERROR: register_driver() failed: %d\n", ret);
       goto errout_with_nxmutex;
     }
 
-  fb->vtable->priv = fb;
+  vtable->priv = fb;
-
   return OK;
 
 errout_with_nxmutex:
@@ -1529,3 +1515,51 @@ errout_with_fb:
   kmm_free(fb);
   return ret;
 }
+
+/****************************************************************************
+ * Name: fb_register
+ *
+ * Description:
+ *   Register the framebuffer character device at /dev/fbN where N is the
+ *   display number if the devices supports only a single plane.  If the
+ *   hardware supports multiple color planes, then the device will be
+ *   registered at /dev/fbN.M where N is the again display number but M
+ *   is the display plane.
+ *
+ * Input Parameters:
+ *   display - The display number for the case of boards supporting multiple
+ *             displays or for hardware that supports multiple
+ *             layers (each layer is consider a display).  Typically zero.
+ *   plane   - Identifies the color plane on hardware that supports separate
+ *             framebuffer "planes" for each color component.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned success; a negated errno value is returned on any
+ *   failure.
+ *
+ ****************************************************************************/
+
+int fb_register(int display, int plane)
+{
+  FAR struct fb_vtable_s *vtable;
+  int ret;
+
+  /* Initialize the frame buffer device. */
+
+  ret = up_fbinitialize(display);
+  if (ret < 0)
+    {
+      gerr("ERROR: up_fbinitialize() failed for display %d: %d\n",
+           display, ret);
+      return ret;
+    }
+
+  vtable = up_fbgetvplane(display, plane);
+  if (vtable == NULL)
+    {
+      gerr("ERROR: up_fbgetvplane() failed, vplane=%d\n", plane);
+      return -EINVAL;
+    }
+
+  return fb_register_device(display, plane, vtable);
+}

include/nuttx/video/fb.h

@@ -1056,6 +1056,33 @@ int fb_remove_paninfo(FAR struct fb_vtable_s *vtable, int overlay);
 
 int fb_paninfo_count(FAR struct fb_vtable_s *vtable, int overlay);
 
+/****************************************************************************
+ * Name: fb_register_device
+ *
+ * Description:
+ *   Register the framebuffer character device at /dev/fbN where N is the
+ *   display number if the devices supports only a single plane.  If the
+ *   hardware supports multiple color planes, then the device will be
+ *   registered at /dev/fbN.M where N is the again display number but M
+ *   is the display plane.
+ *
+ * Input Parameters:
+ *   display - The display number for the case of boards supporting multiple
+ *             displays or for hardware that supports multiple
+ *             layers (each layer is consider a display).  Typically zero.
+ *   plane   - Identifies the color plane on hardware that supports separate
+ *             framebuffer "planes" for each color component.
+ *   vtable  - Pointer to framebuffer's virtual table.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned success; a negated errno value is returned on any
+ *   failure.
+ *
+ ****************************************************************************/
+
+int fb_register_device(int display, int plane,
+                       FAR struct fb_vtable_s *vtable);
+
 /****************************************************************************
  * Name: fb_register
  *