drm/rockchip: framebuffer: Add support /dev/graphics/fb0 read

For support some application only can support framebuffer display
framework and need to read display buffer from /dev/graphics/fb0.

besides, you need to add the following patch to get kvddr:

rockchip_gem_create_with_handle()@file:
drivers/gpu/drm/rockchip/rockchip_drm_gem.c

-rk_obj = rockchip_gem_create_object(drm, size, false, flags);
+rk_obj = rockchip_gem_create_object(drm, size, true, flags);

Change-Id: Iec83dba8295268ba418e802a1cf5eeccd3880ab5
Signed-off-by: Sandy Huang <hjc@rock-chips.com>

Author: sandy-huang

drivers/gpu/drm/rockchip/rockchip_drm_fb.c

@@ -100,6 +100,8 @@ rockchip_fb_alloc(struct drm_device *dev, struct drm_mode_fb_cmd2 *mode_cmd,
 {
 	struct rockchip_drm_fb *rockchip_fb;
 	struct rockchip_gem_object *rk_obj;
+	struct rockchip_drm_private *private = dev->dev_private;
+	struct drm_fb_helper *fb_helper = private->fbdev_helper;
 	int ret = 0;
 	int i;
 
@@ -125,6 +127,9 @@ rockchip_fb_alloc(struct drm_device *dev, struct drm_mode_fb_cmd2 *mode_cmd,
 			rk_obj = to_rockchip_obj(obj[i]);
 			rockchip_fb->dma_addr[i] = rk_obj->dma_addr;
 			rockchip_fb->kvaddr[i] = rk_obj->kvaddr;
+			private->fbdev_bo = &rk_obj->base;
+			if (fb_helper && fb_helper->fbdev && rk_obj->kvaddr)
+				fb_helper->fbdev->screen_base = rk_obj->kvaddr;
 		}
 #ifndef MODULE
 	} else if (logo) {

drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c

@@ -60,6 +60,8 @@ static struct fb_ops rockchip_drm_fbdev_ops = {
 	.fb_set_par	= drm_fb_helper_set_par,
 	.fb_blank	= drm_fb_helper_blank,
 	.fb_pan_display	= drm_fb_helper_pan_display,
+	.fb_read	= drm_fb_helper_sys_read,
+	.fb_write	= drm_fb_helper_sys_write,
 	.fb_setcmap	= drm_fb_helper_setcmap,
 	.fb_dmabuf_export	= rockchip_fbdev_get_dma_buf,
 };