[PATCH v2 2/2] drm/fb_helper: implement ioctl FBIO_WAITFORVSYNC

[Maxime Ripard]

From: Stefan Christ <s.christ@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_fb_helper.c | 55 ++++++++++++++++++++++++++++++++++-
 include/drm/drm_fb_helper.h     |  5 ++-
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index e934b541feea..39a3532e311c 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1234,6 +1234,61 @@ 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;
+	unsigned int i;
+	int ret = 0;
+
+	drm_modeset_lock_all(dev);
+	if (!drm_fb_helper_is_bound(fb_helper)) {
+		drm_modeset_unlock_all(dev);
+		return -EBUSY;
+	}
+
+	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 enabled.
+			 */
+			if (!crtc->enabled)
+				continue;
+
+			ret = drm_crtc_vblank_get(crtc);
+			if (!ret) {
+				drm_crtc_wait_one_vblank(crtc);
+				drm_crtc_vblank_put(crtc);
+			}
+		}
+		goto unlock;
+	default:
+		ret = -ENOTTY;
+	}
+
+unlock:
+	drm_modeset_unlock_all(dev);
+	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..460be9d9fa98 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 +287,8 @@ 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);
-- 
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