From: Stefan Christ <s.chr...@phytec.de>

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.chr...@phytec.de>
Signed-off-by: Maxime Ripard <maxime.rip...@free-electrons.com>
---
 drivers/gpu/drm/drm_fb_helper.c | 63 ++++++++++++++++++++++++++++++++++-
 include/drm/drm_fb_helper.h     | 12 +++++-
 2 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index c6de87abaca8..15ee9641c725 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1240,6 +1240,69 @@ 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: fbdev registered by the helper
+ * @cmd: ioctl command
+ * @arg: ioctl argument
+ *
+ * A helper to implement the standard fbdev ioctl. Only
+ * FBIO_WAITFORVSYNC is implemented for now.
+ */
+int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
+                       unsigned long arg)
+{
+       struct drm_fb_helper *fb_helper = info->par;
+       struct drm_device *dev = fb_helper->dev;
+       struct drm_mode_set *mode_set;
+       struct drm_crtc *crtc;
+       u32 karg;
+       int ret = 0;
+
+       mutex_lock(&dev->mode_config.mutex);
+       if (!drm_fb_helper_is_bound(fb_helper)) {
+               ret = -EBUSY;
+               goto unlock;
+       }
+
+       switch (cmd) {
+       case FBIO_WAITFORVSYNC:
+               if (get_user(karg, (__u32 __user *)arg)) {
+                       ret = -EFAULT;
+                       goto unlock;
+               }
+
+               if (karg >= fb_helper->crtc_count) {
+                       ret = -EINVAL;
+                       goto unlock;
+               }
+
+               mode_set = &fb_helper->crtc_info[karg].mode_set;
+               crtc = mode_set->crtc;
+
+               /*
+                * Only wait for a vblank event if the CRTC is
+                * enabled, otherwise just don't do anythintg,
+                * not even report an error.
+                */
+               ret = drm_crtc_vblank_get(crtc);
+               if (!ret) {
+                       drm_crtc_wait_one_vblank(crtc);
+                       drm_crtc_vblank_put(crtc);
+               }
+
+               ret = 0;
+               goto unlock;
+       default:
+               ret = -ENOTTY;
+       }
+
+unlock:
+       mutex_unlock(&dev->mode_config.mutex);
+       return ret;
+}
+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 975deedd593e..2891888c6e41 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -230,7 +230,8 @@ struct drm_fb_helper {
        .fb_blank       = drm_fb_helper_blank, \
        .fb_pan_display = drm_fb_helper_pan_display, \
        .fb_debug_enter = drm_fb_helper_debug_enter, \
-       .fb_debug_leave = drm_fb_helper_debug_leave
+       .fb_debug_leave = drm_fb_helper_debug_leave, \
+       .fb_ioctl       = drm_fb_helper_ioctl
 
 #ifdef CONFIG_DRM_FBDEV_EMULATION
 void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper 
*helper,
@@ -286,6 +287,9 @@ void drm_fb_helper_set_suspend_unlocked(struct 
drm_fb_helper *fb_helper,
 
 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);
@@ -377,6 +381,12 @@ static inline int drm_fb_helper_setcmap(struct fb_cmap 
*cmap,
        return 0;
 }
 
+static inline int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
+                                     unsigned long arg)
+{
+       return 0;
+}
+
 static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 {
 }
-- 
git-series 0.8.11
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