/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * DRM based mode setting test program
 * Copyright 2008 Tungsten Graphics
 *   Jakob Bornecrantz <jakob@tungstengraphics.com>
 * Copyright 2008 Intel Corporation
 *   Jesse Barnes <jesse.barnes@intel.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "graphics_drm.h"

#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>

#include <memory>

#include <android-base/macros.h>
#include <android-base/stringprintf.h>
#include <android-base/unique_fd.h>
#include <string>
#include <drm_fourcc.h>
#include <xf86drm.h>
#include <xf86drmMode.h>
#include <sstream>

#include "minui/minui.h"

#define find_prop_id(_res, type, Type, obj_id, prop_name, prop_id)    \
  do {                                                                \
    int j = 0;                                                        \
    int prop_count = 0;                                               \
    struct Type *obj = NULL;                                          \
    obj = (_res);                                                     \
    if (!obj || main_monitor_##type->type##_id != (obj_id)){          \
      prop_id = 0;                                                    \
      break;                                                          \
    }                                                                 \
    prop_count = (int)obj->props->count_props;                        \
    for (j = 0; j < prop_count; ++j)                                  \
      if (!strcmp(obj->props_info[j]->name, (prop_name)))             \
        break;                                                        \
    (prop_id) = (j == prop_count)?                                    \
      0 : obj->props_info[j]->prop_id;                                \
  } while (0)

#define add_prop(res, type, Type, id, id_name, id_val) \
  find_prop_id(res, type, Type, id, id_name, prop_id); \
  if (prop_id)                                         \
    drmModeAtomicAddProperty(atomic_req, id, prop_id, id_val);

/**
 * enum sde_rm_topology_name - HW resource use case in use by connector
 * @SDE_RM_TOPOLOGY_NONE:                 No topology in use currently
 * @SDE_RM_TOPOLOGY_SINGLEPIPE:           1 LM, 1 PP, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_SINGLEPIPE_DSC:       1 LM, 1 DSC, 1 PP, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_SINGLEPIPE_VDC:       1 LM, 1 VDC, 1 PP, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_DUALPIPE:             2 LM, 2 PP, 2 INTF/WB
 * @SDE_RM_TOPOLOGY_DUALPIPE_DSC:         2 LM, 2 DSC, 2 PP, 2 INTF/WB
 * @SDE_RM_TOPOLOGY_DUALPIPE_3DMERGE:     2 LM, 2 PP, 3DMux, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_DUALPIPE_3DMERGE_DSC: 2 LM, 2 PP, 3DMux, 1 DSC, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_DUALPIPE_3DMERGE_VDC: 2 LM, 2 PP, 3DMux, 1 VDC, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_DUALPIPE_DSCMERGE:    2 LM, 2 PP, 2 DSC Merge, 1 INTF/WB
 * @SDE_RM_TOPOLOGY_PPSPLIT:              1 LM, 2 PPs, 2 INTF/WB
 * @SDE_RM_TOPOLOGY_QUADPIPE_3DMERGE      4 LM, 4 PP, 3DMux, 2 INTF
 * @SDE_RM_TOPOLOGY_QUADPIPE_3DMERGE_DSC  4 LM, 4 PP, 3DMux, 3 DSC, 2 INTF
 * @SDE_RM_TOPOLOGY_QUADPIPE_DSCMERE      4 LM, 4 PP, 4 DSC Merge, 2 INTF
 * @SDE_RM_TOPOLOGY_QUADPIPE_DSC4HSMERGE  4 LM, 4 PP, 4 DSC Merge, 1 INTF
 */

static uint32_t get_lm_number(const std::string &topology) {
  if (topology == "sde_singlepipe") return 1;
  if (topology == "sde_singlepipe_dsc") return 1;
  if (topology == "sde_singlepipe_vdc") return 1;
  if (topology == "sde_dualpipe") return 2;
  if (topology == "sde_dualpipe_dsc") return 2;
  if (topology == "sde_dualpipe_vdc") return 2;
  if (topology == "sde_dualpipemerge") return 2;
  if (topology == "sde_dualpipemerge_dsc") return 2;
  if (topology == "sde_dualpipemerge_vdc") return 2;
  if (topology == "sde_dualpipe_dscmerge") return 2;
  if (topology == "sde_ppsplit") return 1;
  if (topology == "sde_quadpipemerge") return 4;
  if (topology == "sde_quadpipe_3dmerge_dsc") return 4;
  if (topology == "sde_quadpipe_dscmerge") return 4;
  if (topology == "sde_quadpipe_dsc4hsmerge") return 4;
  return DEFAULT_NUM_LMS;
}

static uint32_t get_topology_lm_number(int fd, uint32_t blob_id) {
  uint32_t num_lm = DEFAULT_NUM_LMS;

  drmModePropertyBlobRes *blob = drmModeGetPropertyBlob(fd, blob_id);
  if (!blob) {
    return num_lm;
  }

  const char *fmt_str = (const char *)(blob->data);
  std::stringstream stream(fmt_str);
  std::string line = {};
  const std::string topology = "topology=";

  while (std::getline(stream, line)) {
    if (line.find(topology) != std::string::npos) {
        num_lm = get_lm_number(std::string(line, topology.length()));
        break;
    }
  }

  drmModeFreePropertyBlob(blob);
  return num_lm;
}

static int find_plane_prop_id(uint32_t obj_id, const char *prop_name,
                              Plane *plane_res) {
  int i, j = 0;
  int prop_count = 0;
  struct Plane *obj = NULL;

  for (i = 0; i < NUM_PLANES; ++i) {
    obj = &plane_res[i];
    if (!obj || obj->plane->plane_id != obj_id)
      continue;
    prop_count = (int)obj->props->count_props;
    for (j = 0; j < prop_count; ++j)
      if (!strcmp(obj->props_info[j]->name, prop_name))
       return obj->props_info[j]->prop_id;
    break;
  }

  return 0;
}

static int atomic_add_prop_to_plane(Plane *plane_res, drmModeAtomicReq *req,
                                    uint32_t obj_id, const char *prop_name,
                                    uint64_t value) {
  uint32_t prop_id;

  prop_id = find_plane_prop_id(obj_id, prop_name, plane_res);
  if (prop_id == 0) {
    printf("Could not find obj_id = %d\n", obj_id);
    return -EINVAL;
  }

  if (drmModeAtomicAddProperty(req, obj_id, prop_id, value) < 0) {
    printf("Could not add prop_id = %d for obj_id %d\n",
            prop_id, obj_id);
    return -EINVAL;
  }

  return 0;
}

int MinuiBackendDrm::AtomicPopulatePlane(int plane, drmModeAtomicReqPtr atomic_req) {
  uint32_t src_x, src_y, src_w, src_h;
  uint32_t crtc_x, crtc_y, crtc_w, crtc_h;
  int width = main_monitor_crtc->mode.hdisplay;
  int height = main_monitor_crtc->mode.vdisplay;
  int zpos = 0;

  src_y = 0;
  src_w = width/number_of_lms;
  src_h =  height;
  crtc_y = 0;
  crtc_w = width/number_of_lms;
  crtc_h = height;
  src_x = (width/number_of_lms) * plane;
  crtc_x = (width/number_of_lms) * plane;

  /* populate z-order property required for 4 layer mixer */
  if (number_of_lms == 4)
    zpos = plane >> 1;

  atomic_add_prop_to_plane(plane_res, atomic_req,
                           plane_res[plane].plane->plane_id, "zpos", zpos);

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "FB_ID",
                               GRSurfaceDrms[current_buffer]->fb_id))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "SRC_X", src_x << 16))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "SRC_Y", src_y << 16))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "SRC_W", src_w << 16))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "SRC_H", src_h << 16))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "CRTC_X", crtc_x))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "CRTC_Y", crtc_y))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "CRTC_W", crtc_w))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "CRTC_H", crtc_h))
    return -EINVAL;

  if (atomic_add_prop_to_plane(plane_res, atomic_req,
                               plane_res[plane].plane->plane_id, "CRTC_ID",
                               main_monitor_crtc->crtc_id))
    return -EINVAL;

  return 0;
}

int MinuiBackendDrm::TeardownPipeline(drmModeAtomicReqPtr atomic_req) {
  uint32_t i, prop_id;
  int ret;

  /* During suspend, tear down pipeline */
  add_prop(&conn_res, connector, Connector, main_monitor_connector->connector_id, "CRTC_ID", 0);
  add_prop(&crtc_res, crtc, Crtc, main_monitor_crtc->crtc_id, "MODE_ID", 0);
  add_prop(&crtc_res, crtc, Crtc, main_monitor_crtc->crtc_id, "ACTIVE", 0);

  for(i = 0; i < number_of_lms; i++) {
    ret = atomic_add_prop_to_plane(plane_res, atomic_req,
                                   plane_res[i].plane->plane_id, "CRTC_ID", 0);
    if (ret < 0) {
      printf("Failed to tear down plane %d\n", i);
      return ret;
    }

    if (drmModeAtomicAddProperty(atomic_req, plane_res[i].plane->plane_id, fb_prop_id, 0) < 0) {
      printf("Failed to add property for plane_id=%d\n", plane_res[i].plane->plane_id);
      return -EINVAL;
    }
  }

  return 0;
}

int MinuiBackendDrm::SetupPipeline(drmModeAtomicReqPtr atomic_req) {
  uint32_t i, prop_id;
  int ret;

  for(i = 0; i < number_of_lms; i++) {
    add_prop(&conn_res, connector, Connector, main_monitor_connector->connector_id,
         "CRTC_ID", main_monitor_crtc->crtc_id);
    add_prop(&crtc_res, crtc, Crtc, main_monitor_crtc->crtc_id, "MODE_ID", crtc_res.mode_blob_id);
    add_prop(&crtc_res, crtc, Crtc, main_monitor_crtc->crtc_id, "ACTIVE", 1);
  }

  /* Setup planes */
  for(i = 0; i < number_of_lms; i++) {
    ret = AtomicPopulatePlane(i, atomic_req);
    if (ret < 0) {
      printf("Error populating plane_id = %d\n", plane_res[i].plane->plane_id);
      return ret;
    }
  }

  return 0;
}

GRSurfaceDrm::~GRSurfaceDrm() {
  if (mmapped_buffer_) {
    munmap(mmapped_buffer_, row_bytes * height);
  }

  if (fb_id) {
    if (drmModeRmFB(drm_fd_, fb_id) != 0) {
      perror("Failed to drmModeRmFB");
      // Falling through to free other resources.
    }
  }

  if (handle) {
    drm_gem_close gem_close = {};
    gem_close.handle = handle;

    if (drmIoctl(drm_fd_, DRM_IOCTL_GEM_CLOSE, &gem_close) != 0) {
      perror("Failed to DRM_IOCTL_GEM_CLOSE");
    }
  }
}

static int drm_format_to_bpp(uint32_t format) {
  switch (format) {
    case DRM_FORMAT_ABGR8888:
    case DRM_FORMAT_BGRA8888:
    case DRM_FORMAT_RGBX8888:
    case DRM_FORMAT_RGBA8888:
    case DRM_FORMAT_ARGB8888:
    case DRM_FORMAT_BGRX8888:
    case DRM_FORMAT_XBGR8888:
    case DRM_FORMAT_XRGB8888:
      return 32;
    case DRM_FORMAT_RGB565:
      return 16;
    default:
      printf("Unknown format %d\n", format);
      return 32;
  }
}

std::unique_ptr<GRSurfaceDrm> GRSurfaceDrm::Create(int drm_fd, int width, int height) {
  uint32_t format;
  PixelFormat pixel_format = gr_pixel_format();
  // PixelFormat comes in byte order, whereas DRM_FORMAT_* uses little-endian
  // (external/libdrm/include/drm/drm_fourcc.h). Note that although drm_fourcc.h also defines a
  // macro of DRM_FORMAT_BIG_ENDIAN, it doesn't seem to be actually supported (see the discussion
  // in https://lists.freedesktop.org/archives/amd-gfx/2017-May/008560.html).
  if (pixel_format == PixelFormat::ABGR) {
    format = DRM_FORMAT_RGBA8888;
  } else if (pixel_format == PixelFormat::BGRA) {
    format = DRM_FORMAT_ARGB8888;
  } else if (pixel_format == PixelFormat::RGBX) {
    format = DRM_FORMAT_XBGR8888;
  } else if (pixel_format == PixelFormat::ARGB) {
    format = DRM_FORMAT_BGRA8888;
  } else {
    format = DRM_FORMAT_RGB565;
  }

  drm_mode_create_dumb create_dumb = {};
  create_dumb.height = height;
  create_dumb.width = width;
  create_dumb.bpp = drm_format_to_bpp(format);
  create_dumb.flags = 0;

  if (drmIoctl(drm_fd, DRM_IOCTL_MODE_CREATE_DUMB, &create_dumb) != 0) {
    perror("Failed to DRM_IOCTL_MODE_CREATE_DUMB");
    return nullptr;
  }

  // Cannot use std::make_unique to access non-public ctor.
  auto surface = std::unique_ptr<GRSurfaceDrm>(new GRSurfaceDrm(
      width, height, create_dumb.pitch, create_dumb.bpp / 8, drm_fd, create_dumb.handle));

  uint32_t handles[4], pitches[4], offsets[4];

  handles[0] = surface->handle;
  pitches[0] = create_dumb.pitch;
  offsets[0] = 0;
  if (drmModeAddFB2(drm_fd, width, height, format, handles, pitches, offsets, &surface->fb_id, 0) !=
      0) {
    perror("Failed to drmModeAddFB2");
    return nullptr;
  }

  drm_mode_map_dumb map_dumb = {};
  map_dumb.handle = create_dumb.handle;
  if (drmIoctl(drm_fd, DRM_IOCTL_MODE_MAP_DUMB, &map_dumb) != 0) {
    perror("Failed to DRM_IOCTL_MODE_MAP_DUMB");
    return nullptr;
  }

  auto mmapped = mmap(nullptr, surface->height * surface->row_bytes, PROT_READ | PROT_WRITE,
                      MAP_SHARED, drm_fd, map_dumb.offset);
  if (mmapped == MAP_FAILED) {
    perror("Failed to mmap()");
    return nullptr;
  }
  surface->mmapped_buffer_ = static_cast<uint8_t*>(mmapped);
  return surface;
}

int MinuiBackendDrm::DrmDisableCrtc(drmModeAtomicReqPtr atomic_req) {
  return TeardownPipeline(atomic_req);
}

int MinuiBackendDrm::DrmEnableCrtc(drmModeAtomicReqPtr atomic_req){
  return SetupPipeline(atomic_req);
}

void MinuiBackendDrm::Blank(bool blank) {
  int ret = 0;

  if (blank == current_blank_state)
    return;

  drmModeAtomicReqPtr atomic_req = drmModeAtomicAlloc();
  if (!atomic_req) {
     printf("Atomic Alloc failed\n");
     return;
  }

  if (blank)
    ret = DrmDisableCrtc(atomic_req);
  else
    ret = DrmEnableCrtc(atomic_req);

  if (!ret)
    ret = drmModeAtomicCommit(drm_fd, atomic_req, DRM_MODE_ATOMIC_ALLOW_MODESET, NULL);

  if (!ret) {
    printf("Atomic Commit failed, rc = %d\n", ret);
    current_blank_state = blank;
  }

  drmModeAtomicFree(atomic_req);
}

static drmModeCrtc* find_crtc_for_connector(int fd, drmModeRes* resources,
                                            drmModeConnector* connector) {
  // Find the encoder. If we already have one, just use it.
  drmModeEncoder* encoder;
  if (connector->encoder_id) {
    encoder = drmModeGetEncoder(fd, connector->encoder_id);
  } else {
    encoder = nullptr;
  }

  int32_t crtc;
  if (encoder && encoder->crtc_id) {
    crtc = encoder->crtc_id;
    drmModeFreeEncoder(encoder);
    return drmModeGetCrtc(fd, crtc);
  }

  // Didn't find anything, try to find a crtc and encoder combo.
  crtc = -1;
  for (int i = 0; i < connector->count_encoders; i++) {
    encoder = drmModeGetEncoder(fd, connector->encoders[i]);

    if (encoder) {
      for (int j = 0; j < resources->count_crtcs; j++) {
        if (!(encoder->possible_crtcs & (1 << j))) continue;
        crtc = resources->crtcs[j];
        break;
      }
      if (crtc >= 0) {
        drmModeFreeEncoder(encoder);
        return drmModeGetCrtc(fd, crtc);
      }
    }
  }

  return nullptr;
}

static drmModeConnector* find_used_connector_by_type(int fd, drmModeRes* resources, unsigned type) {
  for (int i = 0; i < resources->count_connectors; i++) {
    drmModeConnector* connector = drmModeGetConnector(fd, resources->connectors[i]);
    if (connector) {
      if ((connector->connector_type == type) && (connector->connection == DRM_MODE_CONNECTED) &&
          (connector->count_modes > 0)) {
        return connector;
      }
      drmModeFreeConnector(connector);
    }
  }
  return nullptr;
}

static drmModeConnector* find_first_connected_connector(int fd, drmModeRes* resources) {
  for (int i = 0; i < resources->count_connectors; i++) {
    drmModeConnector* connector;

    connector = drmModeGetConnector(fd, resources->connectors[i]);
    if (connector) {
      if ((connector->count_modes > 0) && (connector->connection == DRM_MODE_CONNECTED))
        return connector;

      drmModeFreeConnector(connector);
    }
  }
  return nullptr;
}

drmModeConnector* MinuiBackendDrm::FindMainMonitor(int fd, drmModeRes* resources,
                                                   uint32_t* mode_index) {
  /* Look for LVDS/eDP/DSI connectors. Those are the main screens. */
  static constexpr unsigned kConnectorPriority[] = {
    DRM_MODE_CONNECTOR_LVDS,
    DRM_MODE_CONNECTOR_eDP,
    DRM_MODE_CONNECTOR_DSI,
  };

  drmModeConnector* main_monitor_connector = nullptr;
  unsigned i = 0;
  do {
    main_monitor_connector = find_used_connector_by_type(fd, resources, kConnectorPriority[i]);
    i++;
  } while (!main_monitor_connector && i < arraysize(kConnectorPriority));

  /* If we didn't find a connector, grab the first one that is connected. */
  if (!main_monitor_connector) {
    main_monitor_connector = find_first_connected_connector(fd, resources);
  }

  /* If we still didn't find a connector, give up and return. */
  if (!main_monitor_connector) return nullptr;

  *mode_index = 0;
  for (int modes = 0; modes < main_monitor_connector->count_modes; modes++) {
    if (main_monitor_connector->modes[modes].type & DRM_MODE_TYPE_PREFERRED) {
      *mode_index = modes;
      break;
    }
  }

  return main_monitor_connector;
}

void MinuiBackendDrm::DisableNonMainCrtcs(int fd, drmModeRes* resources, drmModeCrtc* main_crtc) {
  uint32_t prop_id;
  drmModeAtomicReqPtr atomic_req = drmModeAtomicAlloc();

  for (int i = 0; i < resources->count_connectors; i++) {
    drmModeConnector* connector = drmModeGetConnector(fd, resources->connectors[i]);
    drmModeCrtc* crtc = find_crtc_for_connector(fd, resources, connector);
    if (crtc->crtc_id != main_crtc->crtc_id) {
      // Switching to atomic commit. Given only crtc, we can only set ACTIVE = 0
      // to disable any Nonmain CRTCs
      find_prop_id(&crtc_res, crtc, Crtc, crtc->crtc_id, "ACTIVE", prop_id);
      if (prop_id == 0)
        return;

      if (drmModeAtomicAddProperty(atomic_req, main_monitor_crtc->crtc_id, prop_id, 0) < 0)
        return;
    }
    drmModeFreeCrtc(crtc);
  }

  if (!drmModeAtomicCommit(drm_fd, atomic_req,DRM_MODE_ATOMIC_ALLOW_MODESET, NULL))
    printf("Atomic Commit failed in DisableNonMainCrtcs\n");

  drmModeAtomicFree(atomic_req);
}

void MinuiBackendDrm::UpdatePlaneFB() {
  uint32_t i, prop_id;

  /* Set atomic req */
  drmModeAtomicReqPtr atomic_req = drmModeAtomicAlloc();
  if (!atomic_req) {
     printf("Atomic Alloc failed. Could not update fb_id\n");
     return;
  }

  /* Add conn-crtc association property required
   * for driver to recognize quadpipe topology.
   */
  add_prop(&conn_res, connector, Connector, main_monitor_connector->connector_id,
           "CRTC_ID", main_monitor_crtc->crtc_id);

  /* Add property */
  for(i = 0; i < number_of_lms; i++)
    drmModeAtomicAddProperty(atomic_req, plane_res[i].plane->plane_id,
                             fb_prop_id, GRSurfaceDrms[current_buffer]->fb_id);

  /* Commit changes */
  int32_t ret;
  ret = drmModeAtomicCommit(drm_fd, atomic_req,
                 DRM_MODE_ATOMIC_ALLOW_MODESET, NULL);

  drmModeAtomicFree(atomic_req);

  if (ret)
    printf("Atomic commit failed ret=%d\n", ret);
}

GRSurface* MinuiBackendDrm::Init() {
  drmModeRes* res = nullptr;
  drm_fd = -1;

  number_of_lms = DEFAULT_NUM_LMS;
  /* Consider DRM devices in order. */
  for (int i = 0; i < DRM_MAX_MINOR; i++) {
    auto dev_name = android::base::StringPrintf(DRM_DEV_NAME, DRM_DIR_NAME, i);
    android::base::unique_fd fd(open(dev_name.c_str(), O_RDWR | O_CLOEXEC));
    if (fd == -1) continue;

    /* We need dumb buffers. */
    if (uint64_t cap = 0; drmGetCap(fd.get(), DRM_CAP_DUMB_BUFFER, &cap) != 0 || cap == 0) {
      continue;
    }

    res = drmModeGetResources(fd.get());
    if (!res) {
      continue;
    }

    /* Use this device if it has at least one connected monitor. */
    if (res->count_crtcs > 0 && res->count_connectors > 0) {
      if (find_first_connected_connector(fd.get(), res)) {
        drm_fd = fd.release();
        break;
      }
    }

    drmModeFreeResources(res);
    res = nullptr;
  }

  if (drm_fd == -1 || res == nullptr) {
    perror("Failed to find/open a drm device");
    return nullptr;
  }

  uint32_t selected_mode;
  main_monitor_connector = FindMainMonitor(drm_fd, res, &selected_mode);
  if (!main_monitor_connector) {
    fprintf(stderr, "Failed to find main_monitor_connector\n");
    drmModeFreeResources(res);
    close(drm_fd);
    return nullptr;
  }

  main_monitor_crtc = find_crtc_for_connector(drm_fd, res, main_monitor_connector);
  if (!main_monitor_crtc) {
    fprintf(stderr, "Failed to find main_monitor_crtc\n");
    drmModeFreeResources(res);
    close(drm_fd);
    return nullptr;
  }

  DisableNonMainCrtcs(drm_fd, res, main_monitor_crtc);

  main_monitor_crtc->mode = main_monitor_connector->modes[selected_mode];

  int width = main_monitor_crtc->mode.hdisplay;
  int height = main_monitor_crtc->mode.vdisplay;

  drmModeFreeResources(res);

  GRSurfaceDrms[0] = GRSurfaceDrm::Create(drm_fd, width, height);
  GRSurfaceDrms[1] = GRSurfaceDrm::Create(drm_fd, width, height);
  if (!GRSurfaceDrms[0] || !GRSurfaceDrms[1]) {
    return nullptr;
  }

  current_buffer = 0;

  drmSetClientCap(drm_fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
  drmSetClientCap(drm_fd, DRM_CLIENT_CAP_ATOMIC, 1);

  /* Get possible plane_ids */
  drmModePlaneRes *plane_options = drmModeGetPlaneResources(drm_fd);
  if (!plane_options || !plane_options->planes || (plane_options->count_planes < number_of_lms))
    return NULL;

  /* Set crtc resources */
  crtc_res.props = drmModeObjectGetProperties(drm_fd,
                      main_monitor_crtc->crtc_id,
                      DRM_MODE_OBJECT_CRTC);
  if (!crtc_res.props)
    return NULL;

  crtc_res.props_info = static_cast<drmModePropertyRes **>
                           (calloc(crtc_res.props->count_props,
                           sizeof(crtc_res.props_info)));
  if (!crtc_res.props_info)
    return NULL;
  else
    for (int j = 0; j < (int)crtc_res.props->count_props; ++j)
      crtc_res.props_info[j] = drmModeGetProperty(drm_fd,
                                   crtc_res.props->props[j]);

  /* Set connector resources */
  conn_res.props = drmModeObjectGetProperties(drm_fd,
                     main_monitor_connector->connector_id,
                     DRM_MODE_OBJECT_CONNECTOR);
  if (!conn_res.props)
    return NULL;

  conn_res.props_info = static_cast<drmModePropertyRes **>
                         (calloc(conn_res.props->count_props,
                         sizeof(conn_res.props_info)));
  if (!conn_res.props_info)
    return NULL;
  else {
    for (int j = 0; j < (int)conn_res.props->count_props; ++j) {

      conn_res.props_info[j] = drmModeGetProperty(drm_fd,
                                 conn_res.props->props[j]);

      /* Get preferred mode information and extract the
       * number of layer mixers needed from the topology name.
       */
      if (!strcmp(conn_res.props_info[j]->name, "mode_properties")) {
        number_of_lms = get_topology_lm_number(drm_fd, conn_res.props->prop_values[j]);
        printf("number of lms in topology %d\n", number_of_lms);
      }
    }
  }

  /* Set plane resources */
  for(uint32_t i = 0; i < number_of_lms; ++i) {
    plane_res[i].plane = drmModeGetPlane(drm_fd, plane_options->planes[i]);
    if (!plane_res[i].plane)
      return NULL;
  }

  for (uint32_t i = 0; i < number_of_lms; ++i) {
    struct Plane *obj = &plane_res[i];
    unsigned int j;
    obj->props = drmModeObjectGetProperties(drm_fd, obj->plane->plane_id,
                    DRM_MODE_OBJECT_PLANE);
    if (!obj->props)
      continue;
    obj->props_info = static_cast<drmModePropertyRes **>
                         (calloc(obj->props->count_props, sizeof(*obj->props_info)));
    if (!obj->props_info)
      continue;
    for (j = 0; j < obj->props->count_props; ++j)
      obj->props_info[j] = drmModeGetProperty(drm_fd, obj->props->props[j]);
  }

  drmModeFreePlaneResources(plane_options);
  plane_options = NULL;

  /* Setup pipe and blob_id */
  if (drmModeCreatePropertyBlob(drm_fd, &main_monitor_crtc->mode, sizeof(drmModeModeInfo),
      &crtc_res.mode_blob_id)) {
    printf("failed to create mode blob\n");
    return NULL;
  }

  /* Save fb_prop_id*/
  uint32_t prop_id;
  prop_id = find_plane_prop_id(plane_res[0].plane->plane_id, "FB_ID", plane_res);
  fb_prop_id = prop_id;

  Blank(false);

  return GRSurfaceDrms[0].get();
}

GRSurface* MinuiBackendDrm::Flip() {
  UpdatePlaneFB();

  current_buffer = 1 - current_buffer;
  return GRSurfaceDrms[current_buffer].get();
}

MinuiBackendDrm::~MinuiBackendDrm() {
  Blank(true);
  drmModeDestroyPropertyBlob(drm_fd, crtc_res.mode_blob_id);
  drmModeFreeCrtc(main_monitor_crtc);
  drmModeFreeConnector(main_monitor_connector);
  close(drm_fd);
  drm_fd = -1;
}