backend/native: Share drmModeAddFB code

With all the three paths this is quite a handful of code, and it was mostly
duplicated in two places. A follow-up patch would need to introduce a third
copy of it. Therefore move the code into a helper function.

There are two behavioral changes:

- The format error now prints the string code as well, because it is easy to
  read.

- The g_debug() in init_dumb_fb() is removed. Did not seem useful.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/810

src/backends/native/meta-drm-buffer-gbm.c

@@ -57,16 +57,8 @@ acquire_swapped_buffer (MetaDrmBufferGbm  *buffer_gbm,
                         gboolean           use_modifiers,
                         GError           **error)
 {
-  uint32_t handles[4] = {0, 0, 0, 0};
+  MetaGpuKmsFBArgs fb_args = { 0, };
-  uint32_t strides[4] = {0, 0, 0, 0};
-  uint32_t offsets[4] = {0, 0, 0, 0};
-  uint64_t modifiers[4] = {0, 0, 0, 0};
-  uint32_t width, height;
-  uint32_t format;
   struct gbm_bo *bo;
-  int kms_fd;
-
-  kms_fd = meta_gpu_kms_get_fd (buffer_gbm->gpu_kms);
 
   bo = gbm_surface_lock_front_buffer (buffer_gbm->surface);
   if (!bo)
@@ -81,10 +73,10 @@ acquire_swapped_buffer (MetaDrmBufferGbm  *buffer_gbm,
   if (gbm_bo_get_handle_for_plane (bo, 0).s32 == -1)
     {
       /* Failed to fetch handle to plane, falling back to old method */
-      strides[0] = gbm_bo_get_stride (bo);
+      fb_args.strides[0] = gbm_bo_get_stride (bo);
-      handles[0] = gbm_bo_get_handle (bo).u32;
+      fb_args.handles[0] = gbm_bo_get_handle (bo).u32;
-      offsets[0] = 0;
+      fb_args.offsets[0] = 0;
-      modifiers[0] = DRM_FORMAT_MOD_INVALID;
+      fb_args.modifiers[0] = DRM_FORMAT_MOD_INVALID;
     }
   else
     {
@@ -92,76 +84,24 @@ acquire_swapped_buffer (MetaDrmBufferGbm  *buffer_gbm,
 
       for (i = 0; i < gbm_bo_get_plane_count (bo); i++)
         {
-          strides[i] = gbm_bo_get_stride_for_plane (bo, i);
+          fb_args.strides[i] = gbm_bo_get_stride_for_plane (bo, i);
-          handles[i] = gbm_bo_get_handle_for_plane (bo, i).u32;
+          fb_args.handles[i] = gbm_bo_get_handle_for_plane (bo, i).u32;
-          offsets[i] = gbm_bo_get_offset (bo, i);
+          fb_args.offsets[i] = gbm_bo_get_offset (bo, i);
-          modifiers[i] = gbm_bo_get_modifier (bo);
+          fb_args.modifiers[i] = gbm_bo_get_modifier (bo);
         }
      }
 
-  width = gbm_bo_get_width (bo);
+  fb_args.width = gbm_bo_get_width (bo);
-  height = gbm_bo_get_height (bo);
+  fb_args.height = gbm_bo_get_height (bo);
-  format = gbm_bo_get_format (bo);
+  fb_args.format = gbm_bo_get_format (bo);
 
-  if (use_modifiers && modifiers[0] != DRM_FORMAT_MOD_INVALID)
+  if (!meta_gpu_kms_add_fb (buffer_gbm->gpu_kms,
+                            use_modifiers,
+                            &fb_args,
+                            &buffer_gbm->fb_id, error))
     {
-      if (drmModeAddFB2WithModifiers (kms_fd,
+      gbm_surface_release_buffer (buffer_gbm->surface, bo);
-                                      width, height,
+      return FALSE;
-                                      format,
-                                      handles,
-                                      strides,
-                                      offsets,
-                                      modifiers,
-                                      &buffer_gbm->fb_id,
-                                      DRM_MODE_FB_MODIFIERS))
-        {
-          g_set_error (error,
-                       G_IO_ERROR,
-                       g_io_error_from_errno (errno),
-                       "drmModeAddFB2WithModifiers failed: %s",
-                       g_strerror (errno));
-          gbm_surface_release_buffer (buffer_gbm->surface, bo);
-          return FALSE;
-        }
-    }
-  else if (drmModeAddFB2 (kms_fd,
-                          width,
-                          height,
-                          format,
-                          handles,
-                          strides,
-                          offsets,
-                          &buffer_gbm->fb_id,
-                          0))
-    {
-      if (format != DRM_FORMAT_XRGB8888)
-        {
-          g_set_error (error,
-                       G_IO_ERROR,
-                       G_IO_ERROR_FAILED,
-                       "drmModeAddFB does not support format 0x%x",
-                       format);
-          gbm_surface_release_buffer (buffer_gbm->surface, bo);
-          return FALSE;
-        }
-
-      if (drmModeAddFB (kms_fd,
-                        width,
-                        height,
-                        24,
-                        32,
-                        strides[0],
-                        handles[0],
-                        &buffer_gbm->fb_id))
-        {
-          g_set_error (error,
-                       G_IO_ERROR,
-                       g_io_error_from_errno (errno),
-                       "drmModeAddFB failed: %s",
-                       g_strerror (errno));
-          gbm_surface_release_buffer (buffer_gbm->surface, bo);
-          return FALSE;
-        }
     }
 
   buffer_gbm->bo = bo;

src/backends/native/meta-gpu-kms.c

@@ -25,6 +25,7 @@
 #include "backends/native/meta-gpu-kms.h"
 
 #include <drm.h>
+#include <drm_fourcc.h>
 #include <errno.h>
 #include <poll.h>
 #include <string.h>
@@ -63,6 +64,80 @@ struct _MetaGpuKms
 
 G_DEFINE_TYPE (MetaGpuKms, meta_gpu_kms, META_TYPE_GPU)
 
+gboolean
+meta_gpu_kms_add_fb (MetaGpuKms              *gpu_kms,
+                     gboolean                 use_modifiers,
+                     const MetaGpuKmsFBArgs  *args,
+                     uint32_t                *fb_id_out,
+                     GError                 **error)
+{
+  MetaDrmFormatBuf tmp;
+  uint32_t fb_id;
+
+  if (use_modifiers && args->modifiers[0] != DRM_FORMAT_MOD_INVALID)
+    {
+      if (drmModeAddFB2WithModifiers (gpu_kms->fd,
+                                      args->width,
+                                      args->height,
+                                      args->format,
+                                      args->handles,
+                                      args->strides,
+                                      args->offsets,
+                                      args->modifiers,
+                                      &fb_id,
+                                      DRM_MODE_FB_MODIFIERS))
+        {
+          g_set_error (error,
+                       G_IO_ERROR,
+                       g_io_error_from_errno (errno),
+                       "drmModeAddFB2WithModifiers failed: %s",
+                       g_strerror (errno));
+          return FALSE;
+        }
+    }
+  else if (drmModeAddFB2 (gpu_kms->fd,
+                          args->width,
+                          args->height,
+                          args->format,
+                          args->handles,
+                          args->strides,
+                          args->offsets,
+                          &fb_id,
+                          0))
+    {
+      if (args->format != DRM_FORMAT_XRGB8888)
+        {
+          g_set_error (error,
+                       G_IO_ERROR,
+                       G_IO_ERROR_FAILED,
+                       "drmModeAddFB does not support format '%s' (0x%x)",
+                       meta_drm_format_to_string (&tmp, args->format),
+                       args->format);
+          return FALSE;
+        }
+
+      if (drmModeAddFB (gpu_kms->fd,
+                        args->width,
+                        args->height,
+                        24,
+                        32,
+                        args->strides[0],
+                        args->handles[0],
+                        &fb_id))
+        {
+          g_set_error (error,
+                       G_IO_ERROR,
+                       g_io_error_from_errno (errno),
+                       "drmModeAddFB failed: %s",
+                       g_strerror (errno));
+          return FALSE;
+        }
+    }
+
+    *fb_id_out = fb_id;
+    return TRUE;
+}
+
 gboolean
 meta_gpu_kms_is_crtc_active (MetaGpuKms *gpu_kms,
                              MetaCrtc   *crtc)

src/backends/native/meta-gpu-kms.h

@@ -77,4 +77,21 @@ MetaGpuKmsFlipClosureContainer * meta_gpu_kms_wrap_flip_closure (MetaGpuKms *gpu
 
 void meta_gpu_kms_flip_closure_container_free (MetaGpuKmsFlipClosureContainer *closure_container);
 
+typedef struct _MetaGpuKmsFBArgs
+{
+  uint32_t width;
+  uint32_t height;
+  uint32_t format;
+  uint32_t handles[4];
+  uint32_t offsets[4];
+  uint32_t strides[4];
+  uint64_t modifiers[4];
+} MetaGpuKmsFBArgs;
+
+gboolean meta_gpu_kms_add_fb (MetaGpuKms              *gpu_kms,
+                              gboolean                 use_modifiers,
+                              const MetaGpuKmsFBArgs  *args,
+                              uint32_t                *fb_id_out,
+                              GError                 **error);
+
 #endif /* META_GPU_KMS_H */

src/backends/native/meta-renderer-native.c

@@ -2534,9 +2534,11 @@ init_dumb_fb (MetaDumbBuffer  *dumb_fb,
   uint32_t fb_id = 0;
   void *map;
   int kms_fd;
-  uint32_t handles[4] = { 0, };
+  MetaGpuKmsFBArgs fb_args = {
-  uint32_t pitches[4] = { 0, };
+    .width = width,
-  uint32_t offsets[4] = { 0, };
+    .height = height,
+    .format = format,
+  };
 
   kms_fd = meta_gpu_kms_get_fd (gpu_kms);
 
@@ -2554,42 +2556,11 @@ init_dumb_fb (MetaDumbBuffer  *dumb_fb,
       goto err_ioctl;
     }
 
-  handles[0] = create_arg.handle;
+  fb_args.handles[0] = create_arg.handle;
-  pitches[0] = create_arg.pitch;
+  fb_args.strides[0] = create_arg.pitch;
 
-  if (drmModeAddFB2 (kms_fd, width, height, format,
+  if (!meta_gpu_kms_add_fb (gpu_kms, FALSE, &fb_args, &fb_id, error))
-                     handles, pitches, offsets,
+    goto err_add_fb;
-                     &fb_id, 0) != 0)
-    {
-      g_debug ("drmModeAddFB2 failed (%s), falling back to drmModeAddFB",
-               g_strerror (errno));
-    }
-
-  if (fb_id == 0)
-    {
-      if (format != DRM_FORMAT_XRGB8888)
-        {
-          g_set_error (error, G_IO_ERROR,
-                       G_IO_ERROR_FAILED,
-                       "drmModeAddFB does not support format 0x%x",
-                       format);
-          goto err_add_fb;
-        }
-
-      if (drmModeAddFB (kms_fd, width, height,
-                        24 /* depth of RGBX8888 */,
-                        32 /* bpp of RGBX8888 */,
-                        create_arg.pitch,
-                        create_arg.handle,
-                        &fb_id) != 0)
-        {
-          g_set_error (error, G_IO_ERROR,
-                       G_IO_ERROR_FAILED,
-                       "drmModeAddFB failed: %s",
-                       g_strerror (errno));
-          goto err_add_fb;
-        }
-    }
 
   map_arg = (struct drm_mode_map_dumb) {
     .handle = create_arg.handle