nuttx/graphics/vnc/server/vnc_fbdev.c

/****************************************************************************
 * graphics/vnc/server/vnc_fbdev.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#if defined(CONFIG_VNCSERVER_DEBUG) && !defined(CONFIG_DEBUG_GRAPHICS)
#  undef  CONFIG_DEBUG_ERROR
#  undef  CONFIG_DEBUG_WARN
#  undef  CONFIG_DEBUG_INFO
#  undef  CONFIG_DEBUG_GRAPHICS_ERROR
#  undef  CONFIG_DEBUG_GRAPHICS_WARN
#  undef  CONFIG_DEBUG_GRAPHICS_INFO
#  define CONFIG_DEBUG_ERROR          1
#  define CONFIG_DEBUG_WARN           1
#  define CONFIG_DEBUG_INFO           1
#  define CONFIG_DEBUG_GRAPHICS       1
#  define CONFIG_DEBUG_GRAPHICS_ERROR 1
#  define CONFIG_DEBUG_GRAPHICS_WARN  1
#  define CONFIG_DEBUG_GRAPHICS_INFO  1
#endif
#include <debug.h>

#include <nuttx/kthread.h>
#include <nuttx/video/fb.h>
#include <nuttx/video/vnc.h>

#include "vnc_server.h"

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* This structure provides the frame buffer interface and also incapulates
 * information about the frame buffer instances for each display.
 */

struct vnc_fbinfo_s
{
  /* The publicly visible frame buffer interface.  This must appear first
   * so that struct vnc_fbinfo_s is cast compatible with struct fb_vtable_s.
   */

  struct fb_vtable_s vtable;

  /* Our private per-display information */

  bool initialized;           /* True: This instance has been initialized */
  uint8_t display;            /* Display number */
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/* Get information about the video controller configuration and the
 * configuration of each color plane.
 */

static int up_getvideoinfo(FAR struct fb_vtable_s *vtable,
                           FAR struct fb_videoinfo_s *vinfo);
static int up_getplaneinfo(FAR struct fb_vtable_s *vtable, int planeno,
                           FAR struct fb_planeinfo_s *pinfo);

/* The following are provided only if the video hardware supports RGB color
 * mapping.
 */

#ifdef CONFIG_FB_CMAP
static int up_getcmap(FAR struct fb_vtable_s *vtable,
                      FAR struct fb_cmap_s *cmap);
static int up_putcmap(FAR struct fb_vtable_s *vtable,
                      FAR const struct fb_cmap_s *cmap);
#endif

/* The following are provided only if the video hardware supports a hardware
 * cursor.
 */

#ifdef CONFIG_FB_HWCURSOR
static int up_getcursor(FAR struct fb_vtable_s *vtable,
                        FAR struct fb_cursorattrib_s *attrib);
static int up_setcursor(FAR struct fb_vtable_s *vtable,
                        FAR struct fb_setcursor_s *settings);
#endif

/****************************************************************************
 * Private Data
 ****************************************************************************/

/* Current cursor position */

#ifdef CONFIG_FB_HWCURSOR
static struct fb_cursorpos_s g_cpos;

/* Current cursor size */

#ifdef CONFIG_FB_HWCURSORSIZE
static struct fb_cursorsize_s g_csize;
#endif
#endif

/* The framebuffer objects, one for each configured display. */

static struct vnc_fbinfo_s g_fbinfo[RFB_MAX_DISPLAYS];

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* Used to synchronize the server thread with the framebuffer driver.
 * NOTE:  This depends on the fact that all zero is correct initial state
 * for the semaphores.
 */

struct fb_startup_s g_fbstartup[RFB_MAX_DISPLAYS];

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_getvideoinfo
 ****************************************************************************/

static int up_getvideoinfo(FAR struct fb_vtable_s *vtable,
                           FAR struct fb_videoinfo_s *vinfo)
{
  FAR struct vnc_fbinfo_s *fbinfo = (FAR struct vnc_fbinfo_s *)vtable;
  FAR struct vnc_session_s *session;

  ginfo("vtable=%p vinfo=%p\n", vtable, vinfo);

  DEBUGASSERT(fbinfo != NULL && vinfo != NULL);
  if (fbinfo != NULL && vinfo != NULL)
    {
      DEBUGASSERT(fbinfo->display >= 0 &&
                  fbinfo->display < RFB_MAX_DISPLAYS);
      session = g_vnc_sessions[fbinfo->display];

      if (session == NULL || session->state != VNCSERVER_RUNNING)
        {
          gerr("ERROR: session is not connected\n");
          return -ENOTCONN;
        }

      /* Return the requested video info.  We are committed to using the
       * configured color format in the framebuffer, but performing color
       * conversions on the fly for the remote framebuffer as necessary.
       */

      vinfo->fmt     = RFB_COLORFMT;
      vinfo->xres    = CONFIG_VNCSERVER_SCREENWIDTH;
      vinfo->yres    = CONFIG_VNCSERVER_SCREENHEIGHT;
      vinfo->nplanes = 1;

      return OK;
    }

  gerr("ERROR: Invalid arguments\n");
  return -EINVAL;
}

/****************************************************************************
 * Name: up_getplaneinfo
 ****************************************************************************/

static int up_getplaneinfo(FAR struct fb_vtable_s *vtable, int planeno,
                           FAR struct fb_planeinfo_s *pinfo)
{
  FAR struct vnc_fbinfo_s *fbinfo = (FAR struct vnc_fbinfo_s *)vtable;
  FAR struct vnc_session_s *session;

  ginfo("vtable=%p planeno=%d pinfo=%p\n", vtable, planeno, pinfo);

  DEBUGASSERT(fbinfo != NULL && pinfo != NULL && planeno == 0);
  if (fbinfo != NULL && pinfo != NULL && planeno == 0)
    {
      DEBUGASSERT(fbinfo->display >= 0 &&
                  fbinfo->display < RFB_MAX_DISPLAYS);
      session = g_vnc_sessions[fbinfo->display];

      if (session == NULL || session->state != VNCSERVER_RUNNING)
        {
          gerr("ERROR: session is not connected\n");
          return -ENOTCONN;
        }

      DEBUGASSERT(session->fb != NULL);

      /* Return the requested plane info.  We are committed to using the
       * configured bits-per-pixels in the framebuffer, but performing color
       * conversions on the fly for the remote framebuffer as necessary.
       */

      pinfo->fbmem    = (FAR void *)session->fb;
      pinfo->fblen    = RFB_SIZE;
      pinfo->stride   = RFB_STRIDE;
      pinfo->display  = fbinfo->display;
      pinfo->bpp      = RFB_BITSPERPIXEL;

      return OK;
    }

  gerr("ERROR: Returning EINVAL\n");
  return -EINVAL;
}

/****************************************************************************
 * Name: up_getcmap
 ****************************************************************************/

#ifdef CONFIG_FB_CMAP
static int up_getcmap(FAR struct fb_vtable_s *vtable,
                      FAR struct fb_cmap_s *cmap)
{
  FAR struct vnc_fbinfo_s *fbinfo = (FAR struct vnc_fbinfo_s *)vtable;
  FAR struct vnc_session_s *session;
  int i;

  ginfo("vtable=%p cmap=%p\n", vtable, cmap);

  DEBUGASSERT(fbinfo != NULL && cmap != NULL);

  if (fbinfo != NULL && cmap != NULL)
    {
      DEBUGASSERT(fbinfo->display >= 0 &&
                  fbinfo->display < RFB_MAX_DISPLAYS);
      session = g_vnc_sessions[fbinfo->display];

      if (session == NULL || session->state != VNCSERVER_RUNNING)
        {
          gerr("ERROR: session is not connected\n");
          return -ENOTCONN;
        }

      ginfo("first=%d len=%d\n", vcmap->first, cmap->len);
#warning Missing logic

      return OK;
    }

  gerr("ERROR: Returning EINVAL\n");
  return -EINVAL;
}
#endif

/****************************************************************************
 * Name: up_putcmap
 ****************************************************************************/

#ifdef CONFIG_FB_CMAP
static int up_putcmap(FAR struct fb_vtable_s *vtable,
                      FAR const struct fb_cmap_s *cmap)
{
  FAR struct vnc_fbinfo_s *fbinfo = (FAR struct vnc_fbinfo_s *)vtable;
  FAR struct vnc_session_s *session;
  int i;

  ginfo("vtable=%p cmap=%p\n", vtable, cmap);

  DEBUGASSERT(fbinfo != NULL && cmap != NULL);

  if (fbinfo != NULL && cmap != NULL)
    {
      DEBUGASSERT(fbinfo->display >= 0 &&
                  fbinfo->display < RFB_MAX_DISPLAYS);
      session = g_vnc_sessions[fbinfo->display];

      if (session == NULL || session->state != VNCSERVER_RUNNING)
        {
          gerr("ERROR: session is not connected\n");
          return -ENOTCONN;
        }

      ginfo("first=%d len=%d\n", vcmap->first, cmap->len);
#warning Missing logic

      return OK;
    }

  gerr("ERROR: Returning EINVAL\n");
  return -EINVAL;
}
#endif

/****************************************************************************
 * Name: up_getcursor
 ****************************************************************************/

#ifdef CONFIG_FB_HWCURSOR
static int up_getcursor(FAR struct fb_vtable_s *vtable,
                        FAR struct fb_cursorattrib_s *attrib)
{
  FAR struct vnc_fbinfo_s *fbinfo = (FAR struct vnc_fbinfo_s *)vtable;
  FAR struct vnc_session_s *session;
  int i;

  ginfo("vtable=%p attrib=%p\n", vtable, attrib);

  DEBUGASSERT(fbinfo != NULL && attrib != NULL);

  if (fbinfo != NULL && attrib != NULL)
    {
      DEBUGASSERT(fbinfo->display >= 0 &&
                  fbinfo->display < RFB_MAX_DISPLAYS);
      session = g_vnc_sessions[fbinfo->display];

      if (session == NULL || session->state != VNCSERVER_RUNNING)
        {
          gerr("ERROR: session is not connected\n");
          return -ENOTCONN;
        }

#warning Missing logic

      return OK;
    }

  gerr("ERROR: Returning EINVAL\n");
  return -EINVAL;
}
#endif

/****************************************************************************
 * Name: up_setcursor
 ****************************************************************************/

#ifdef CONFIG_FB_HWCURSOR
static int up_setcursor(FAR struct fb_vtable_s *vtable,
                       FAR struct fb_setcursor_s *settings)
{
  FAR struct vnc_fbinfo_s *fbinfo = (FAR struct vnc_fbinfo_s *)vtable;
  FAR struct vnc_session_s *session;
  int i;

  ginfo("vtable=%p settings=%p\n", vtable, settings);

  DEBUGASSERT(fbinfo != NULL && settings != NULL);

  if (fbinfo != NULL && settings != NULL)
    {
      DEBUGASSERT(fbinfo->display >= 0 &&
                  fbinfo->display < RFB_MAX_DISPLAYS);
      session = g_vnc_sessions[fbinfo->display];

      if (session == NULL || session->state != VNCSERVER_RUNNING)
        {
          gerr("ERROR: session is not connected\n");
          return -ENOTCONN;
        }

      ginfo("flags:   %02x\n", settings->flags);
      if ((settings->flags & FB_CUR_SETPOSITION) != 0)
        {
#warning Missing logic
        }

#ifdef CONFIG_FB_HWCURSORSIZE
      if ((settings->flags & FB_CUR_SETSIZE) != 0)
        {
#warning Missing logic
        }
#endif

#ifdef CONFIG_FB_HWCURSORIMAGE
      if ((settings->flags & FB_CUR_SETIMAGE) != 0)
        {
#warning Missing logic
        }
#endif

      return OK;
    }

  gerr("ERROR: Returning EINVAL\n");
  return -EINVAL;
}
#endif

/****************************************************************************
 * Name: vnc_start_server
 *
 * Description:
 *   Start the VNC server.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *
 * Returned Value:
 *   Zero is returned on success; a negated errno value is returned on any
 *   failure.
 *
 ****************************************************************************/

static int vnc_start_server(int display)
{
  FAR char *argv[2];
  char str[8];
  pid_t pid;

  DEBUGASSERT(display >= 0 && display < RFB_MAX_DISPLAYS);

  /* Check if the server is already running */

  if (g_vnc_sessions[display] != NULL)
    {
      DEBUGASSERT(g_vnc_sessions[display]->state >= VNCSERVER_INITIALIZED);
      return OK;
    }

  /* Start the VNC server kernel thread. */

  ginfo("Starting the VNC server for display %d\n", display);

  g_fbstartup[display].result = -EBUSY;
  nxsem_reset(&g_fbstartup[display].fbinit, 0);
  nxsem_reset(&g_fbstartup[display].fbconnect, 0);

  /* Format the kernel thread arguments (ASCII.. yech) */

  itoa(display, str, 10);
  argv[0] = str;
  argv[1] = NULL;

  pid = kthread_create("vnc_server", CONFIG_VNCSERVER_PRIO,
                       CONFIG_VNCSERVER_STACKSIZE,
                       (main_t)vnc_server, argv);
  if (pid < 0)
    {
      gerr("ERROR: Failed to start the VNC server: %d\n", (int)pid);
      return (int)pid;
    }

  return OK;
}

/****************************************************************************
 * Name: vnc_wait_start
 *
 * Description:
 *   Wait for the server to be started.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *
 * Returned Value:
 *   Zero is returned on success; a negated errno value is returned on any
 *   failure.
 *
 ****************************************************************************/

static inline int vnc_wait_start(int display)
{
  int ret;

  /* Check if there has been a session allocated yet.  This is one of the
   * first things that the VNC server will do with the kernel thread is
   * started.  But we might be here before the thread has gotten that far.
   *
   * If it has been allocated, then wait until it is in the INIITIALIZED
   * state.  The INITIAILIZED states indicates that the session structure
   * has been allocated and fully initialized.
   */

  while (g_vnc_sessions[display] == NULL ||
         g_vnc_sessions[display]->state == VNCSERVER_UNINITIALIZED)
    {
      /* The server is not yet running.  Wait for the server to post the FB
       * semaphore.  In certain error situations, the server may post the
       * semaphore, then reset it to zero.  There are are certainly race
       * conditions here, but I think none that are fatal.
       */

      ret = nxsem_wait_uninterruptible(&g_fbstartup[display].fbinit);
      if (ret < 0)
        {
          return ret;
        }
    }

  return OK;
}

/****************************************************************************
 * Name: vnc_wait_connect
 *
 * Description:
 *   Wait for the server to be connected to the VNC client.  We can do
 *   nothing until that connection is established.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *
 * Returned Value:
 *   Zero is returned on success; a negated errno value is returned on any
 *   failure.
 *
 ****************************************************************************/

static inline int vnc_wait_connect(int display)
{
  int ret;

  /* Check if there has been a session allocated yet.  This is one of the
   * first things that the VNC server will do with the kernel thread is
   * started.  But we might be here before the thread has gotten that far.
   *
   * If it has been allocated, then wait until it is in the RUNNING state.
   * The RUNNING state indicates that the server has started, it has
   * established a connection with the VNC client, it is negotiated
   * encodings and framebuffer characteristics, and it has started the
   * updater thread.  The server is now ready to receive Client-to-Server
   * messages and to perform remote framebuffer updates.
   */

  while (g_vnc_sessions[display] == NULL ||
         g_vnc_sessions[display]->state != VNCSERVER_RUNNING)
    {
      /* The server is not yet running.  Wait for the server to post the FB
       * semaphore.  In certain error situations, the server may post the
       * semaphore, then reset it to zero.  There are are certainly race
       * conditions here, but I think none that are fatal.
       */

      ret = nxsem_wait_uninterruptible(&g_fbstartup[display].fbconnect);
      if (ret < 0)
        {
          return ret;
        }

      /* We were awakened.  A result of -EBUSY means that the negotiation
       * is not complete.  Why would we be awakened in that case?  Some
       * counting semaphore screw-up?
       */

      ret = g_fbstartup[display].result;
      if (ret != -EBUSY)
        {
#ifdef CONFIG_DEBUG_FEATURES
          if (ret < 0)
            {
              DEBUGASSERT(g_vnc_sessions[display] == NULL);
              gerr("ERROR: VNC server startup failed: %d\n", ret);
            }
          else
            {
              DEBUGASSERT(g_vnc_sessions[display] != NULL &&
                          g_vnc_sessions[display]->state ==
                          VNCSERVER_RUNNING);
            }
#endif

          return ret;
        }
    }

  return OK;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_fbinitialize
 *
 * Description:
 *   Initialize the framebuffer video hardware associated with the display.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *
 * Returned Value:
 *   Zero is returned on success; a negated errno value is returned on any
 *   failure.
 *
 ****************************************************************************/

int up_fbinitialize(int display)
{
  int ret;

  DEBUGASSERT(display >= 0 && display < RFB_MAX_DISPLAYS);

  /* Start the VNC server kernel thread. */

  ret = vnc_start_server(display);
  if (ret < 0)
    {
      gerr("ERROR: vnc_start_server() failed: %d\n", ret);
      return ret;
    }

  /* Wait for the VNC client to connect and for the RFB to be ready */

  ret = vnc_wait_connect(display);
  if (ret < 0)
    {
      gerr("ERROR: vnc_wait_connect() failed: %d\n", ret);
    }

  return ret;
}

/****************************************************************************
 * Name: vnc_fbinitialize
 *
 * Description:
 *   Initialize the VNC frame buffer driver.  The VNC frame buffer driver
 *   supports two initialization interfaces:  The standard up_fbinitialize()
 *   that will be called from the graphics layer and this speical
 *   initialization function that can be used only by VNC aware OS logic.
 *
 *   The two initialization functions may be called separated or together in
 *   either order.  The difference is that standard up_fbinitialize(), if
 *   used by itself, will not have any remote mouse or keyboard inputs that
 *   are reported to the VNC framebuffer driver from the remote VNC client.
 *
 *   In the standard graphics architecture, the keyboard/mouse inputs are
 *   received by some application/board specific logic at the highest level
 *   in the architecture via input drivers.  The received keyboard/mouse
 *   input data must then be "injected" into NX where it can they can be
 *   assigned to the window that has focus.  They will eventually be
 *   received by the Window instances via NX callback methods.
 *
 *   NX is a middleware layer in the architecture, below the
 *   application/board specific logic but above the driver level logic.  The
 *   frame buffer driver, on the other hand lies at the very lowest level in
 *   the graphics architecture.  It cannot call upward into the application
 *   nor can it call upward into NX.  So, some other logic.
 *
 *   vnc_fbinitialize() provides an optional, alternative initialization
 *   function.  It is optional because it need not be called.  If it is not
 *   called, however, keyboard/mouse inputs from the remote VNC client will
 *   be lost.  By calling vnc_fbinitialize(), you can provide callout
 *   functions that can be received by logic higher in the architecture.
 *   These higher level callouts can then call nx_kbdin() or nx_mousein() on
 *   behalf of the VNC server.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *   kbdout - If non-NULL, then the pointed-to function will be called to
 *     handle all keyboard input as it is received.  This may be either raw,
 *     ASCII keypress input or encoded keyboard input as determined by
 *     CONFIG_VNCSERVER_KBDENCODE.  See include/nuttx/input/kbd_codec.h.
 *   mouseout - If non-NULL, then the pointed-to function will be called to
 *     handle all mouse input as it is received.
 *   arg - An opaque user provided argument that will be provided when the
 *    callouts are performed.
 *
 * Returned Value:
 *   Zero (OK) is returned on success.  Otherwise, a negated errno value is
 *   returned to indicate the nature of the failure.
 *
 ****************************************************************************/

int vnc_fbinitialize(int display, vnc_kbdout_t kbdout,
                     vnc_mouseout_t mouseout, FAR void *arg)
{
  FAR struct vnc_session_s *session;
  int ret;

  DEBUGASSERT(display >= 0 && display < RFB_MAX_DISPLAYS);

  /* Start the VNC server kernel thread. */

  ret = vnc_start_server(display);
  if (ret < 0)
    {
      gerr("ERROR: vnc_start_server() failed: %d\n", ret);
      return ret;
    }

  /* Wait for the VNC server to start and complete initialization. */

  ret = vnc_wait_start(display);
  if (ret < 0)
    {
      gerr("ERROR: vnc_wait_start() failed: %d\n", ret);
      return ret;
    }

  /* Save the input callout function information in the session structure. */

  session           = g_vnc_sessions[display];
  DEBUGASSERT(session != NULL);

  session->kbdout   = kbdout;
  session->mouseout = mouseout;
  session->arg      = arg;

  return OK;
}

/****************************************************************************
 * Name: up_fbgetvplane
 *
 * Description:
 *   Return a a reference to the framebuffer object for the specified video
 *   plane of the specified plane.  Many OSDs support multiple planes of
 *   video.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *   vplane - Identifies the plane being queried.
 *
 * Returned Value:
 *   A non-NULL pointer to the frame buffer access structure is returned on
 *   success; NULL is returned on any failure.
 *
 ****************************************************************************/

FAR struct fb_vtable_s *up_fbgetvplane(int display, int vplane)
{
  FAR struct vnc_session_s *session;
  FAR struct vnc_fbinfo_s *fbinfo;

  DEBUGASSERT(display >= 0 && display < RFB_MAX_DISPLAYS);
  session = g_vnc_sessions[display];

  /* Verify that the session is still valid */

  if (session == NULL || session->state != VNCSERVER_RUNNING)
    {
      return NULL;
    }

  if (vplane == 0)
    {
      /* Has the framebuffer information been initialized for this display? */

      fbinfo = &g_fbinfo[display];
      if (!fbinfo->initialized)
        {
          fbinfo->vtable.getvideoinfo = up_getvideoinfo,
          fbinfo->vtable.getplaneinfo = up_getplaneinfo,
#ifdef CONFIG_FB_CMAP
          fbinfo->vtable.getcmap      = up_getcmap,
          fbinfo->vtable.putcmap      = up_putcmap,
#endif
#ifdef CONFIG_FB_HWCURSOR
          fbinfo->vtable.getcursor    = up_getcursor,
          fbinfo->vtable.setcursor    = up_setcursor,
#endif
          fbinfo->display             = display;
          fbinfo->initialized         = true;
        }

      return &fbinfo->vtable;
    }
  else
    {
      return NULL;
    }
}

/****************************************************************************
 * Name: up_fbuninitialize
 *
 * Description:
 *   Uninitialize the framebuffer support for the specified display.
 *
 * Input Parameters:
 *   display - In the case of hardware with multiple displays, this
 *     specifies the display.  Normally this is zero.
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void up_fbuninitialize(int display)
{
#if 0 /* Do nothing */
  FAR struct vnc_session_s *session;
  FAR struct vnc_fbinfo_s *fbinfo;

  DEBUGASSERT(display >= 0 && display < RFB_MAX_DISPLAYS);
  session = g_vnc_sessions[display];

  /* Verify that the session is still valid */

  if (session != NULL)
    {
      fbinfo = &g_fbinfo[display];
#warning Missing logic
      UNUSED(session);
      UNUSED(fbinfo);
    }
#endif
}

/****************************************************************************
 * Name: nx_notify_rectangle
 *
 * Description:
 *   When CONFIG_NX_UPDATE=y, then the graphics system will callout to
 *   inform some external module that the display has been updated.  This
 *   would be useful in a couple for cases.
 *
 *   - When a serial LCD is used, but a framebuffer is used to access the
 *     LCD.  In this case, the update callout can be used to refresh the
 *     affected region of the display.
 *
 *   - When VNC is enabled.  This is case, this callout is necessary to
 *     update the remote frame buffer to match the local framebuffer.
 *
 * When this feature is enabled, some external logic must provide this
 * interface.  This is the function that will handle the notification.  It
 * receives the rectangular region that was updated on the provided plane.
 *
 ****************************************************************************/

#ifdef CONFIG_NX_UPDATE
void nx_notify_rectangle(FAR NX_PLANEINFOTYPE *pinfo,
                         FAR const struct nxgl_rect_s *rect)
{
  FAR struct vnc_session_s *session;
  int ret;

  DEBUGASSERT(pinfo != NULL && rect != NULL);

  /* Recover the session information from the display number in the planeinfo
   * structure.
   */

  DEBUGASSERT(pinfo->display >= 0 && pinfo->display < RFB_MAX_DISPLAYS);
  session = g_vnc_sessions[pinfo->display];

  /* Verify that the session is still valid */

  if (session != NULL && session->state == VNCSERVER_RUNNING)
    {
      /* Queue the rectangular update */

      ret = vnc_update_rectangle(session, rect, true);
      if (ret < 0)
        {
          gerr("ERROR: vnc_update_rectangle failed: %d\n", ret);
        }
    }
}
#endif