[PATCH 2/3] drm: fb_helper: implement ioctl FBIO_WAITFORVSYNC

[Stefan Christ]

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