text: /*  RetroArch - A frontend for libretro.
   *  Copyright (C) 2010-2014 - Hans-Kristian Arntzen
   *  Copyright (C) 2011-2017 - Daniel De Matteis
   *
   *  RetroArch is free software: you can redistribute it and/or modify it under the terms
   *  of the GNU General Public License as published by the Free Software Found-
   *  ation, either version 3 of the License, or (at your option) any later version.
   *
   *  RetroArch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
   *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
   *  PURPOSE.  See the GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License along with RetroArch.
   *  If not, see <http://www.gnu.org/licenses/>.
   */
  
  /* KMS/DRM context, running without any window manager.
   * Based on kmscube example by Rob Clark.
   */
  
  #include <stdint.h>
  #include <errno.h>
  #include <string.h>
  #include <unistd.h>
  #include <math.h>
  
  #include <sched.h>
  #include <sys/time.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #include <poll.h>
  
  #include <libdrm/drm.h>
  #include <gbm.h>
  
  #include <lists/dir_list.h>
  #include <string/stdstring.h>
  
  #ifdef HAVE_CONFIG_H
  #include "../../config.h"
  #endif
  
  #include "../../configuration.h"
  #include "../../verbosity.h"
  #include "../../frontend/frontend_driver.h"
  #include "../common/drm_common.h"
  
  #ifdef HAVE_EGL
  #include "../common/egl_common.h"
  #endif
  
  #include "../common/gl_common.h"
  
  #ifdef HAVE_OPENGLES
  
  #ifndef EGL_OPENGL_ES3_BIT_KHR
  #define EGL_OPENGL_ES3_BIT_KHR 0x0040
  #endif
  
  #endif
  
  #ifndef EGL_PLATFORM_GBM_KHR
  #define EGL_PLATFORM_GBM_KHR 0x31D7
  #endif
  
  typedef struct gfx_ctx_drm_data
  {
  #ifdef HAVE_EGL
     egl_ctx_data_t egl;
  #endif
     int fd;
     int interval;
     unsigned fb_width;
     unsigned fb_height;
  
     bool core_hw_context_enable;
     bool waiting_for_flip;
     struct gbm_bo *bo;
     struct gbm_bo *next_bo;
     struct gbm_surface *gbm_surface;
     struct gbm_device  *gbm_dev;
  } gfx_ctx_drm_data_t;
  
  struct drm_fb
  {
     struct gbm_bo *bo;
     uint32_t fb_id;
  };
  
  /*
   * https://github.com/libretro/RetroArch/pull/11590
   * https://www.raspberrypi.org/documentation/configuration/config-txt/video.md
   */
  typedef struct hdmi_timings
  {
     int h_active_pixels; /* horizontal pixels (width) */
     int h_sync_polarity; /* invert hsync polarity */
     int h_front_porch;   /* horizontal forward padding from DE acitve edge */
     int h_sync_pulse;    /* hsync pulse width in pixel clocks */
     int h_back_porch;    /* vertical back padding from DE active edge */
     int v_active_lines;  /* vertical pixels height (lines) */
     int v_sync_polarity; /* invert vsync polarity */
     int v_front_porch;   /* vertical forward padding from DE active edge */
     int v_sync_pulse;    /* vsync pulse width in pixel clocks */
     int v_back_porch;    /* vertical back padding from DE active edge */
     int v_sync_offset_a; /* leave at zero */
     int v_sync_offset_b; /* leave at zero */
     int pixel_rep;       /* leave at zero */
     int frame_rate;      /* screen refresh rate in Hz */
     int interlaced;      /* leave at zero */
     int pixel_freq;      /* clock frequency (width*height*framerate) */
     int aspect_ratio;
  } hdmi_timings_t;
  
  static enum gfx_ctx_api drm_api           = GFX_CTX_NONE;
  static drmModeModeInfo gfx_ctx_crt_switch_mode;
  
  /* Load custom hdmi timings from config */
  bool gfx_ctx_drm_load_mode(drmModeModeInfoPtr modeInfo)
  {
     int ret;
     hdmi_timings_t timings;
     settings_t *settings = config_get_ptr();
     char *crt_switch_timings = settings->arrays.crt_switch_timings;
  
     if(modeInfo != NULL && !string_is_empty(crt_switch_timings)) {
        ret = sscanf(crt_switch_timings, "%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d",
                     &timings.h_active_pixels, &timings.h_sync_polarity, &timings.h_front_porch,
                     &timings.h_sync_pulse, &timings.h_back_porch,
                     &timings.v_active_lines, &timings.v_sync_polarity, &timings.v_front_porch,
                     &timings.v_sync_pulse, &timings.v_back_porch,
                     &timings.v_sync_offset_a, &timings.v_sync_offset_b, &timings.pixel_rep, &timings.frame_rate,
                     &timings.interlaced, &timings.pixel_freq, &timings.aspect_ratio);
        if (ret != 17) {
           RARCH_ERR("[DRM]: malformed mode requested: %s\n", crt_switch_timings);
           return false;
        }
  
        memset(modeInfo, 0, sizeof(drmModeModeInfo));
        modeInfo->clock = timings.pixel_freq / 1000;
        modeInfo->hdisplay = timings.h_active_pixels;
        modeInfo->hsync_start = modeInfo->hdisplay + timings.h_front_porch;
        modeInfo->hsync_end = modeInfo->hsync_start + timings.h_sync_pulse;
        modeInfo->htotal = modeInfo->hsync_end + timings.h_back_porch;
        modeInfo->hskew = 0;
        modeInfo->vdisplay = timings.v_active_lines;
        modeInfo->vsync_start = modeInfo->vdisplay + (timings.v_front_porch * (timings.interlaced ? 2 : 1));
        modeInfo->vsync_end = modeInfo->vsync_start + (timings.v_sync_pulse * (timings.interlaced ? 2 : 1));
        modeInfo->vtotal = modeInfo->vsync_end + (timings.v_back_porch * (timings.interlaced ? 2 : 1));
        modeInfo->vscan = 0; /* TODO: ?? */
        modeInfo->vrefresh = timings.frame_rate;
        modeInfo->flags = timings.interlaced ? DRM_MODE_FLAG_INTERLACE : 0;
        modeInfo->flags |= timings.v_sync_polarity ? DRM_MODE_FLAG_NVSYNC : DRM_MODE_FLAG_PVSYNC;
        modeInfo->flags |= timings.h_sync_polarity ? DRM_MODE_FLAG_NHSYNC : DRM_MODE_FLAG_PHSYNC;
        modeInfo->type = 0;
        snprintf(modeInfo->name, DRM_DISPLAY_MODE_LEN, "CRT_%ux%u_%u",
                 modeInfo->hdisplay, modeInfo->vdisplay, modeInfo->vrefresh);
  
        return true;
     }
  
     return false;
  }
  
  static void drm_fb_destroy_callback(struct gbm_bo *bo, void *data)
  {
     struct drm_fb *fb = (struct drm_fb*)data;
  
     if (fb && fb->fb_id)
        drmModeRmFB(g_drm_fd, fb->fb_id);
  
     free(fb);
  }
  
  static struct drm_fb *drm_fb_get_from_bo(struct gbm_bo *bo)
  {
     int ret;
     unsigned width, height, stride, handle;
     struct drm_fb *fb = (struct drm_fb*)calloc(1, sizeof(*fb));
  
     fb->bo = bo;
  
     width  = gbm_bo_get_width(bo);
     height = gbm_bo_get_height(bo);
     stride = gbm_bo_get_stride(bo);
     handle = gbm_bo_get_handle(bo).u32;
  
     RARCH_LOG("[KMS]: New FB: %ux%u (stride: %u).\n",
           width, height, stride);
  
     ret = drmModeAddFB(g_drm_fd, width, height, 24, 32,
           stride, handle, &fb->fb_id);
     if (ret < 0)
        goto error;
  
     gbm_bo_set_user_data(bo, fb, drm_fb_destroy_callback);
     return fb;
  
  error:
     RARCH_ERR("[KMS]: Failed to create FB: %s\n", strerror(errno));
     free(fb);
     return NULL;
  }
  
  static void gfx_ctx_drm_swap_interval(void *data, int interval)
  {
     gfx_ctx_drm_data_t *drm = (gfx_ctx_drm_data_t*)data;
     drm->interval           = interval;
  
     if (interval > 1)
        RARCH_WARN("[KMS]: Swap intervals > 1 currently not supported. Will use swap interval of 1.\n");
  }
  
  static void gfx_ctx_drm_check_window(void *data, bool *quit,
        bool *resize, unsigned *width, unsigned *height)
  {
     *resize = false;
     *quit   = (bool)frontend_driver_get_signal_handler_state();
  }
  
  static void drm_flip_handler(int fd, unsigned frame,
        unsigned sec, unsigned usec, void *data)
  {
  #if 0
     static unsigned first_page_flip;
     static unsigned last_page_flip;
  
     if (!first_page_flip)
        first_page_flip = frame;
  
     if (last_page_flip)
     {
        unsigned missed = frame - last_page_flip - 1;
        if (missed)
           RARCH_LOG("[KMS]: Missed %u VBlank(s) (Frame: %u, DRM frame: %u).\n",
                 missed, frame - first_page_flip, frame);
     }
  
     last_page_flip = frame;
  #endif
  
     *(bool*)data = false;
  }
  
  static bool gfx_ctx_drm_wait_flip(gfx_ctx_drm_data_t *drm, bool block)
  {
     int timeout = 0;
  
     if (!drm->waiting_for_flip)
        return false;
  
     if (block)
        timeout = -1;
  
     while (drm->waiting_for_flip)
     {
        if (!drm_wait_flip(timeout))
           break;
     }
  
     if (drm->waiting_for_flip)
        return true;
  
     /* Page flip has taken place. */
  
     /* This buffer is not on-screen anymore. Release it to GBM. */
     gbm_surface_release_buffer(drm->gbm_surface, drm->bo);
     /* This buffer is being shown now. */
     drm->bo = drm->next_bo;
  
     return false;
  }
  
  static bool gfx_ctx_drm_queue_flip(gfx_ctx_drm_data_t *drm)
  {
     struct drm_fb *fb = NULL;
  
     drm->next_bo      = gbm_surface_lock_front_buffer(drm->gbm_surface);
     fb                = (struct drm_fb*)gbm_bo_get_user_data(drm->next_bo);
  
     if (!fb)
        fb             = (struct drm_fb*)drm_fb_get_from_bo(drm->next_bo);
  
     if (drmModePageFlip(g_drm_fd, g_crtc_id, fb->fb_id,
           DRM_MODE_PAGE_FLIP_EVENT, &drm->waiting_for_flip) == 0)
        return true;
  
     /* Failed to queue page flip. */
     return false;
  }
  
  static void gfx_ctx_drm_swap_buffers(void *data)
  {
     gfx_ctx_drm_data_t        *drm = (gfx_ctx_drm_data_t*)data;
     settings_t *settings           = config_get_ptr();
     unsigned max_swapchain_images  = settings->uints.video_max_swapchain_images;
  
  #ifdef HAVE_EGL
     egl_swap_buffers(&drm->egl);
  #endif
  
     /* I guess we have to wait for flip to have taken
      * place before another flip can be queued up.
      *
      * If true, we are still waiting for a flip
      * (nonblocking mode, so just drop the frame). */
     if (gfx_ctx_drm_wait_flip(drm, drm->interval))
        return;
  
     drm->waiting_for_flip = gfx_ctx_drm_queue_flip(drm);
  
     /* Triple-buffered page flips */
     if (max_swapchain_images >= 3 &&
           gbm_surface_has_free_buffers(drm->gbm_surface))
        return;
  
     gfx_ctx_drm_wait_flip(drm, true);
  }
  
  static void gfx_ctx_drm_get_video_size(void *data,
        unsigned *width, unsigned *height)
  {
     gfx_ctx_drm_data_t *drm = (gfx_ctx_drm_data_t*)data;
  
     if (!drm)
        return;
  
     *width  = drm->fb_width;
     *height = drm->fb_height;
  }
  
  static void free_drm_resources(gfx_ctx_drm_data_t *drm)
  {
     if (!drm)
        return;
  
     /* Restore original CRTC. */
     drm_restore_crtc();
  
     if (drm->gbm_surface)
        gbm_surface_destroy(drm->gbm_surface);
  
     if (drm->gbm_dev)
        gbm_device_destroy(drm->gbm_dev);
  
     drm_free();
  
     if (drm->fd >= 0)
     {
        if (g_drm_fd >= 0)
        {
           drmDropMaster(g_drm_fd);
           close(drm->fd);
        }
     }
  
     drm->gbm_surface   = NULL;
     drm->gbm_dev       = NULL;
     g_drm_fd           = -1;
  }
  
  static void gfx_ctx_drm_destroy_resources(gfx_ctx_drm_data_t *drm)
  {
     if (!drm)
        return;
  
     /* Make sure we acknowledge all page-flips. */
     gfx_ctx_drm_wait_flip(drm, true);
  
  #ifdef HAVE_EGL
     egl_destroy(&drm->egl);
  #endif
  
     free_drm_resources(drm);
  
     g_drm_mode          = NULL;
     g_crtc_id           = 0;
     g_connector_id      = 0;
  
     drm->fb_width       = 0;
     drm->fb_height      = 0;
  
     drm->bo             = NULL;
     drm->next_bo        = NULL;
  }
  
  static void *gfx_ctx_drm_init(void *video_driver)
  {
     int fd, i;
     unsigned monitor_index;
     unsigned gpu_index                   = 0;
     const char *gpu                      = NULL;
     struct string_list *gpu_descriptors  = NULL;
     settings_t *settings                 = config_get_ptr();
     gfx_ctx_drm_data_t *drm              = (gfx_ctx_drm_data_t*)
        calloc(1, sizeof(gfx_ctx_drm_data_t));
     unsigned video_monitor_index         = settings->uints.video_monitor_index;
  
     if (!drm)
        return NULL;
     drm->fd = -1;
  
     gpu_descriptors = dir_list_new("/dev/dri", NULL, false, true, false, false);
  
  nextgpu:
     free_drm_resources(drm);
  
     if (!gpu_descriptors || gpu_index == gpu_descriptors->size)
     {
        RARCH_ERR("[KMS]: Couldn't find a suitable DRM device.\n");
        goto error;
     }
     gpu = gpu_descriptors->elems[gpu_index++].data;
  
     drm->fd    = open(gpu, O_RDWR);
     if (drm->fd < 0)
     {
        RARCH_WARN("[KMS]: Couldn't open DRM device.\n");
        goto nextgpu;
     }
  
     fd = drm->fd;
  
     if (!drm_get_resources(fd))
        goto nextgpu;
  
     if (!drm_get_connector(fd, video_monitor_index))
        goto nextgpu;
  
     if (!drm_get_encoder(fd))
        goto nextgpu;
  
     drm_setup(fd);
  
     /* Choose the optimal video mode for get_video_size():
       - custom timings from configuration
       - else the current video mode from the CRTC
       - otherwise pick first connector mode */
     if(gfx_ctx_drm_load_mode(&gfx_ctx_crt_switch_mode))
     {
        drm->fb_width  = gfx_ctx_crt_switch_mode.hdisplay;
        drm->fb_height = gfx_ctx_crt_switch_mode.vdisplay;
     }
     else if (g_orig_crtc->mode_valid)
     {
        drm->fb_width  = g_orig_crtc->mode.hdisplay;
        drm->fb_height = g_orig_crtc->mode.vdisplay;
     }
     else
     {
        drm->fb_width  = g_drm_connector->modes[0].hdisplay;
        drm->fb_height = g_drm_connector->modes[0].vdisplay;
     }
  
     drmSetMaster(g_drm_fd);
  
     drm->gbm_dev      = gbm_create_device(fd);
  
     if (!drm->gbm_dev)
     {
        RARCH_WARN("[KMS]: Couldn't create GBM device.\n");
        goto nextgpu;
     }
  
     dir_list_free(gpu_descriptors);
  
     /* Setup the flip handler. */
     g_drm_fds.fd                   = fd;
     g_drm_fds.events               = POLLIN;
     g_drm_evctx.version            = DRM_EVENT_CONTEXT_VERSION;
     g_drm_evctx.page_flip_handler  = drm_flip_handler;
  
     g_drm_fd                       = fd;
  
     return drm;
  
  error:
     dir_list_free(gpu_descriptors);
  
     gfx_ctx_drm_destroy_resources(drm);
  
     if (drm)
        free(drm);
  
     return NULL;
  }
  
  static EGLint *gfx_ctx_drm_egl_fill_attribs(
        gfx_ctx_drm_data_t *drm, EGLint *attr)
  {
     switch (drm_api)
     {
  #ifdef EGL_KHR_create_context
        case GFX_CTX_OPENGL_API:
        {
           bool debug       = false;
  #ifdef HAVE_OPENGL
           unsigned version = drm->egl.major * 1000 + drm->egl.minor;
           bool core        = version >= 3001;
  #ifdef GL_DEBUG
           debug            = true;
  #else
           struct retro_hw_render_callback *hwr = video_driver_get_hw_context();
           debug           = hwr->debug_context;
  #endif
  
           if (core)
           {
              *attr++ = EGL_CONTEXT_MAJOR_VERSION_KHR;
              *attr++ = drm->egl.major;
              *attr++ = EGL_CONTEXT_MINOR_VERSION_KHR;
              *attr++ = drm->egl.minor;
  
              /* Technically, we don't have core/compat until 3.2.
               * Version 3.1 is either compat or not depending
               * on GL_ARB_compatibility. */
              if (version >= 3002)
              {
                 *attr++ = EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR;
                 *attr++ = EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT_KHR;
              }
           }
  
           if (debug)
           {
              *attr++ = EGL_CONTEXT_FLAGS_KHR;
              *attr++ = EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR;
           }
           break;
  #endif
        }
  #endif
  
        case GFX_CTX_OPENGL_ES_API:
  #ifdef HAVE_OPENGLES
           *attr++ = EGL_CONTEXT_CLIENT_VERSION;
           *attr++ = drm->egl.major
              ? (EGLint)drm->egl.major : 2;
  #ifdef EGL_KHR_create_context
           if (drm->egl.minor > 0)
           {
              *attr++ = EGL_CONTEXT_MINOR_VERSION_KHR;
              *attr++ = drm->egl.minor;
           }
  #endif
  #endif
           break;
        case GFX_CTX_NONE:
        default:
           break;
     }
  
     *attr = EGL_NONE;
     return attr;
  }
  
  #ifdef HAVE_EGL
  static bool gbm_choose_xrgb8888_cb(void *display_data, EGLDisplay dpy, EGLConfig config)
  {
     EGLint r, g, b, id;
     (void)display_data;
  
     /* Makes sure we have 8 bit color. */
     if (!egl_get_config_attrib(dpy, config, EGL_RED_SIZE, &r))
        return false;
     if (!egl_get_config_attrib(dpy, config, EGL_GREEN_SIZE, &g))
        return false;
     if (!egl_get_config_attrib(dpy, config, EGL_BLUE_SIZE, &b))
        return false;
  
     if (r != 8 || g != 8 || b != 8)
        return false;
  
     if (!egl_get_config_attrib(dpy, config, EGL_NATIVE_VISUAL_ID, &id))
        return false;
  
     return id == GBM_FORMAT_XRGB8888;
  }
  
  #define DRM_EGL_ATTRIBS_BASE \
     EGL_SURFACE_TYPE,    EGL_WINDOW_BIT, \
     EGL_RED_SIZE,        1, \
     EGL_GREEN_SIZE,      1, \
     EGL_BLUE_SIZE,       1, \
     EGL_ALPHA_SIZE,      0, \
     EGL_DEPTH_SIZE,      0
  
  static bool gfx_ctx_drm_egl_set_video_mode(gfx_ctx_drm_data_t *drm)
  {
     const EGLint *attrib_ptr    = NULL;
     static const EGLint egl_attribs_gl[] = {
        DRM_EGL_ATTRIBS_BASE,
        EGL_RENDERABLE_TYPE, EGL_OPENGL_BIT,
        EGL_NONE,
     };
  
     static const EGLint egl_attribs_gles[] = {
        DRM_EGL_ATTRIBS_BASE,
        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
        EGL_NONE,
     };
  
  #ifdef EGL_KHR_create_context
     static const EGLint egl_attribs_gles3[] = {
        DRM_EGL_ATTRIBS_BASE,
        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT_KHR,
        EGL_NONE,
     };
  #endif
  
  #ifdef HAVE_VG
     static const EGLint egl_attribs_vg[] = {
        DRM_EGL_ATTRIBS_BASE,
        EGL_RENDERABLE_TYPE, EGL_OPENVG_BIT,
        EGL_NONE,
     };
  #endif
     EGLint major;
     EGLint minor;
     EGLint n;
     EGLint egl_attribs[16];
     EGLint *egl_attribs_ptr     = NULL;
     EGLint *attr                = NULL;
  
     switch (drm_api)
     {
        case GFX_CTX_OPENGL_API:
  #ifdef HAVE_OPENGL
           attrib_ptr = egl_attribs_gl;
           break;
        case GFX_CTX_OPENGL_ES_API:
  #ifdef EGL_KHR_create_context
           if (drm->egl.major >= 3)
              attrib_ptr = egl_attribs_gles3;
           else
  #endif
           attrib_ptr = egl_attribs_gles;
  #endif
           break;
        case GFX_CTX_OPENVG_API:
  #ifdef HAVE_VG
           attrib_ptr = egl_attribs_vg;
  #endif
           break;
        case GFX_CTX_NONE:
        default:
           break;
     }
  
  #ifdef HAVE_EGL
     if (!egl_init_context(&drm->egl, EGL_PLATFORM_GBM_KHR,
              (EGLNativeDisplayType)drm->gbm_dev, &major,
              &minor, &n, attrib_ptr, gbm_choose_xrgb8888_cb))
        goto error;
  
     attr            = gfx_ctx_drm_egl_fill_attribs(drm, egl_attribs);
     egl_attribs_ptr = &egl_attribs[0];
  
     if (!egl_create_context(&drm->egl, (attr != egl_attribs_ptr)
              ? egl_attribs_ptr : NULL))
        goto error;
  
     if (!egl_create_surface(&drm->egl, (EGLNativeWindowType)drm->gbm_surface))
        return false;
  
     switch (drm_api)
     {
        case GFX_CTX_OPENGL_API:
        case GFX_CTX_OPENGL_ES_API:
  #if defined(HAVE_OPENGL) || defined(HAVE_OPENGLES)
           gl_clear();
  #endif
           break;
        case GFX_CTX_NONE:
        default:
           break;
     }
  #endif
  
     egl_swap_buffers(drm);
  
     return true;
  
  error:
     egl_report_error();
     return false;
  }
  #endif
  
  static bool gfx_ctx_drm_set_video_mode(void *data,
        unsigned width, unsigned height,
        bool fullscreen)
  {
     float refresh_mod;
     int i, ret                  = 0;
     struct drm_fb *fb           = NULL;
     gfx_ctx_drm_data_t *drm     = (gfx_ctx_drm_data_t*)data;
     settings_t *settings        = config_get_ptr();
     unsigned black_frame_insertion  = settings->uints.video_black_frame_insertion;
     float video_refresh_rate    = settings->floats.video_refresh_rate;
  
     if (!drm)
        return false;
  
     frontend_driver_install_signal_handler();
  
     /* If we use black frame insertion,
      * we fake a 60 Hz monitor for 120 Hz one,
      * etc, so try to match that. */
     refresh_mod = 1.0f / (black_frame_insertion + 1.0f);
  
     /* Find desired video mode, and use that.
      * If not fullscreen, we get desired windowed size,
      * which is not appropriate. */
     if ((width == 0 && height == 0) || !fullscreen)
        g_drm_mode = &g_drm_connector->modes[0];
     else
     {
        /* check if custom hdmi timings were asked */
        if(gfx_ctx_crt_switch_mode.vdisplay > 0)
        {
           RARCH_LOG("[DRM]: custom mode requested: %s\n", gfx_ctx_crt_switch_mode.name);
           g_drm_mode = &gfx_ctx_crt_switch_mode;
        }
        else
        {
           /* Try to match refresh_rate as closely as possible.
            *
            * Lower resolutions tend to have multiple supported
            * refresh rates as well.
            */
           float minimum_fps_diff = 0.0f;
           float mode_vrefresh    = 0.0f;
           drmModeModeInfo *mode;
  
           /* Find best match. */
           for (i = 0; i < g_drm_connector->count_modes; i++) {
              float diff;
              mode = &g_drm_connector->modes[i];
  
              if (width != mode->hdisplay ||
                 height != mode->vdisplay)
                 continue;
  
              mode_vrefresh = drm_calc_refresh_rate(mode);
  
              diff = fabsf(refresh_mod * mode_vrefresh - video_refresh_rate);
  
              if (!g_drm_mode || diff < minimum_fps_diff) {
                 g_drm_mode = mode;
                 minimum_fps_diff = diff;
              }
           }
        }
     }
  
     if (!g_drm_mode)
     {
        RARCH_ERR("[KMS/EGL]: Did not find suitable video mode for %u x %u.\n",
              width, height);
        goto error;
     }
  
     drm->fb_width    = g_drm_mode->hdisplay;
     drm->fb_height   = g_drm_mode->vdisplay;
  
     /* Create GBM surface. */
     drm->gbm_surface = gbm_surface_create(
           drm->gbm_dev,
           drm->fb_width,
           drm->fb_height,
           GBM_FORMAT_XRGB8888,
           GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
  
     if (!drm->gbm_surface)
     {
        RARCH_ERR("[KMS/EGL]: Couldn't create GBM surface.\n");
        goto error;
     }
  
  #ifdef HAVE_EGL
     if (!gfx_ctx_drm_egl_set_video_mode(drm))
        goto error;
  #endif
  
     drm->bo   = gbm_surface_lock_front_buffer(drm->gbm_surface);
  
     fb        = (struct drm_fb*)gbm_bo_get_user_data(drm->bo);
  
     if (!fb)
        fb   = drm_fb_get_from_bo(drm->bo);
  
     ret     = drmModeSetCrtc(g_drm_fd,
           g_crtc_id, fb->fb_id, 0, 0, &g_connector_id, 1, g_drm_mode);
     if (ret < 0)
        goto error;
  
     return true;
  
  error:
     gfx_ctx_drm_destroy_resources(drm);
  
     if (drm)
        free(drm);
  
     return false;
  }
  
  static void gfx_ctx_drm_destroy(void *data)
  {
     gfx_ctx_drm_data_t *drm = (gfx_ctx_drm_data_t*)data;
  
     if (!drm)
        return;
  
     gfx_ctx_drm_destroy_resources(drm);
     free(drm);
  }
  
  static void gfx_ctx_drm_input_driver(void *data,
        const char *joypad_name,
        input_driver_t **input, void **input_data)
  {
  #ifdef HAVE_X11
     settings_t *settings = config_get_ptr();
  
     /* We cannot use the X11 input driver for DRM/KMS */
     if (string_is_equal(settings->arrays.input_driver, "x"))
     {
  #ifdef HAVE_UDEV
        {
           /* Try to set it to udev instead */
           void *udev = input_driver_init_wrap(&input_udev, joypad_name);
           if (udev)
           {
              *input       = &input_udev;
              *input_data  = udev;
              return;
           }
        }
  #endif
  #if defined(__linux__) && !defined(ANDROID)
        {
           /* Try to set it to linuxraw instead */
           void *linuxraw = input_driver_init_wrap(&input_linuxraw, joypad_name);
           if (linuxraw)
           {
              *input       = &input_linuxraw;
              *input_data  = linuxraw;
              return;
           }
        }
  #endif
     }
  #endif
  
     *input      = NULL;
     *input_data = NULL;
  }
  
  static bool gfx_ctx_drm_has_focus(void *data) { return true; }
  
  static bool gfx_ctx_drm_suppress_screensaver(void *data, bool enable) { return false; }
  
  static enum gfx_ctx_api gfx_ctx_drm_get_api(void *data) { return drm_api; }
  
  static bool gfx_ctx_drm_bind_api(void *video_driver,
        enum gfx_ctx_api api, unsigned major, unsigned minor)
  {
     drm_api     = api;
  #ifdef HAVE_EGL
     g_egl_major = major;
     g_egl_minor = minor;
  #endif
  
     switch (api)
     {
        case GFX_CTX_OPENGL_API:
  #if defined(HAVE_EGL) && defined(HAVE_OPENGL)
  
  #ifndef EGL_KHR_create_context
           if ((major * 1000 + minor) >= 3001)
              return false;
  #endif
           return egl_bind_api(EGL_OPENGL_API);
  #else
           break;
  #endif
        case GFX_CTX_OPENGL_ES_API:
  #if defined(HAVE_EGL) && defined(HAVE_OPENGLES)
  
  #ifndef EGL_KHR_create_context
           if (major >= 3)
              return false;
  #endif
           return egl_bind_api(EGL_OPENGL_ES_API);
  #else
           break;
  #endif
        case GFX_CTX_OPENVG_API:
  #if defined(HAVE_EGL) && defined(HAVE_VG)
           return egl_bind_api(EGL_OPENVG_API);
  #endif
        case GFX_CTX_NONE:
        default:
           break;
     }
  
     return false;
  }
  
  static void gfx_ctx_drm_bind_hw_render(void *data, bool enable)
  {
     gfx_ctx_drm_data_t *drm     = (gfx_ctx_drm_data_t*)data;
  
  #ifdef HAVE_EGL
     egl_bind_hw_render(&drm->egl, enable);
  #endif
  }
  
  static uint32_t gfx_ctx_drm_get_flags(void *data)
  {
     uint32_t             flags = 0;
     gfx_ctx_drm_data_t    *drm = (gfx_ctx_drm_data_t*)data;
  
     BIT32_SET(flags, GFX_CTX_FLAGS_CUSTOMIZABLE_SWAPCHAIN_IMAGES);
  
     if (drm->core_hw_context_enable)
        BIT32_SET(flags, GFX_CTX_FLAGS_GL_CORE_CONTEXT);
  
     if (string_is_equal(video_driver_get_ident(), "glcore"))
     {
  #if defined(HAVE_SLANG) && defined(HAVE_SPIRV_CROSS)
        BIT32_SET(flags, GFX_CTX_FLAGS_SHADERS_SLANG);
  #endif
     }
     else
        BIT32_SET(flags, GFX_CTX_FLAGS_SHADERS_GLSL);
  
     return flags;
  }
  
  static void gfx_ctx_drm_set_flags(void *data, uint32_t flags)
  {
     gfx_ctx_drm_data_t *drm     = (gfx_ctx_drm_data_t*)data;
     if (BIT32_GET(flags, GFX_CTX_FLAGS_GL_CORE_CONTEXT))
        drm->core_hw_context_enable = true;
  }
  
  const gfx_ctx_driver_t gfx_ctx_drm = {
     gfx_ctx_drm_init,
     gfx_ctx_drm_destroy,
     gfx_ctx_drm_get_api,
     gfx_ctx_drm_bind_api,
     gfx_ctx_drm_swap_interval,
     gfx_ctx_drm_set_video_mode,
     gfx_ctx_drm_get_video_size,
     drm_get_refresh_rate,
     NULL, /* get_video_output_size */
     NULL, /* get_video_output_prev */
     NULL, /* get_video_output_next */
     NULL, /* get_metrics */
     NULL,
     NULL, /* update_title */
     gfx_ctx_drm_check_window,
     NULL, /* set_resize */
     gfx_ctx_drm_has_focus,
     gfx_ctx_drm_suppress_screensaver,
     false, /* has_windowed */
     gfx_ctx_drm_swap_buffers,
     gfx_ctx_drm_input_driver,
  #ifdef HAVE_EGL
     egl_get_proc_address,
  #else
     NULL,
  #endif
     NULL,
     NULL,
     NULL,
     "kms",
     gfx_ctx_drm_get_flags,
     gfx_ctx_drm_set_flags,
     gfx_ctx_drm_bind_hw_render,
     NULL,
     NULL
  };
  