Implement legacy framebuffer ioctl FBIO_WAITFORVSYNC in the generic
framebuffer emulation driver. Legacy framebuffer users like non kms/drm
based OpenGL(ES)/EGL implementations may require the ioctl to
synchronize drawing or buffer flip for double buffering. It is tested on
the i.MX6.

Code is based on
    
https://github.com/Xilinx/linux-xlnx/blob/master/drivers/gpu/drm/xilinx/xilinx_drm_fb.c#L196

Signed-off-by: Stefan Christ <s.christ at phytec.de>
---
 drivers/gpu/drm/drm_fb_cma_helper.c |  1 +
 drivers/gpu/drm/drm_fb_helper.c     | 43 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_fb_helper.h         |  2 ++
 3 files changed, 46 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c 
b/drivers/gpu/drm/drm_fb_cma_helper.c
index be66042..95657da 100644
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -313,6 +313,7 @@ static struct fb_ops drm_fbdev_cma_ops = {
        .fb_blank       = drm_fb_helper_blank,
        .fb_pan_display = drm_fb_helper_pan_display,
        .fb_setcmap     = drm_fb_helper_setcmap,
+       .fb_ioctl       = drm_fb_helper_ioctl,
 };

 static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 7c2eb75..4d1f9b9 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1167,6 +1167,49 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct 
fb_info *info)
 EXPORT_SYMBOL(drm_fb_helper_setcmap);

 /**
+ * drm_fb_helper_ioctl - legacy ioctl implementation
+ * @info:
+ * @cmd: ioctl like FBIO_WAITFORVSYNC
+ * @arg: ioctl argument
+ */
+int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd, unsigned long 
arg)
+{
+       struct drm_fb_helper *fb_helper = info->par;
+       unsigned int i;
+       int ret = 0;
+
+       switch (cmd) {
+       case FBIO_WAITFORVSYNC:
+               for (i = 0; i < fb_helper->crtc_count; i++) {
+                       struct drm_mode_set *mode_set;
+                       struct drm_crtc *crtc;
+
+                       mode_set = &fb_helper->crtc_info[i].mode_set;
+                       crtc = mode_set->crtc;
+
+                       /*
+                        * Only call drm_crtc_wait_one_vblank for crtcs that
+                        * are currently active.
+                        */
+                       if (!crtc->enabled)
+                               continue;
+
+                       ret = drm_crtc_vblank_get(crtc);
+                       if (!ret) {
+                               drm_crtc_wait_one_vblank(crtc);
+                               drm_crtc_vblank_put(crtc);
+                       }
+               }
+               return ret;
+       default:
+               return -ENOTTY;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL(drm_fb_helper_ioctl);
+
+/**
  * drm_fb_helper_check_var - implementation for ->fb_check_var
  * @var: screeninfo to check
  * @info: fbdev registered by the helper
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 5b4aa35..121af93 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -278,6 +278,8 @@ void drm_fb_helper_set_suspend(struct drm_fb_helper 
*fb_helper, int state);

 int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info);

+int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd, unsigned long 
arg);
+
 int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper);
 int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel);
 int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper);
-- 
1.9.1

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