Hi Thomas,

I love your patch! Yet something to improve:

[auto build test ERROR on next-20200305]
[cannot apply to rockchip/for-next shawnguo/for-next sunxi/sunxi/for-next tegra/for-next linus/master v5.6-rc4 v5.6-rc3 v5.6-rc2 v5.6-rc4]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Thomas-Zimmermann/drm-Convert-drivers-to-drm_simple_encoder_init/20200306-045931
base:    47466dcf84ee66a973ea7d2fca7e582fe9328932
config: mips-randconfig-a001-20200306 (attached as .config)
compiler: mipsel-linux-gcc (GCC) 5.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=5.5.0 make.cross ARCH=mips 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

All errors (new ones prefixed by >>):

   drivers/gpu/drm/vkms/vkms_output.c: In function 'vkms_output_init':
>> drivers/gpu/drm/vkms/vkms_output.c:70:8: error: implicit declaration of function 'drm_simple_encoder_init' [-Werror=implicit-function-declaration]
     ret = drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_VIRTUAL);
           ^
   cc1: some warnings being treated as errors

vim +/drm_simple_encoder_init +70 drivers/gpu/drm/vkms/vkms_output.c

    34	
    35	int vkms_output_init(struct vkms_device *vkmsdev, int index)
    36	{
    37		struct vkms_output *output = &vkmsdev->output;
    38		struct drm_device *dev = &vkmsdev->drm;
    39		struct drm_connector *connector = &output->connector;
    40		struct drm_encoder *encoder = &output->encoder;
    41		struct drm_crtc *crtc = &output->crtc;
    42		struct drm_plane *primary, *cursor = NULL;
    43		int ret;
    44	
    45		primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY, index);
    46		if (IS_ERR(primary))
    47			return PTR_ERR(primary);
    48	
    49		if (enable_cursor) {
    50			cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR, index);
    51			if (IS_ERR(cursor)) {
    52				ret = PTR_ERR(cursor);
    53				goto err_cursor;
    54			}
    55		}
    56	
    57		ret = vkms_crtc_init(dev, crtc, primary, cursor);
    58		if (ret)
    59			goto err_crtc;
    60	
    61		ret = drm_connector_init(dev, connector, &vkms_connector_funcs,
    62					 DRM_MODE_CONNECTOR_VIRTUAL);
    63		if (ret) {
    64			DRM_ERROR("Failed to init connector\n");
    65			goto err_connector;
    66		}
    67	
    68		drm_connector_helper_add(connector, &vkms_conn_helper_funcs);
    69	
  > 70		ret = drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_VIRTUAL);

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org