gbm: Add a gbm_device_get_format_modifier_plane_count function

This allows the user to query the number of planes required by a given
format+modifier combination without having to create a bo or surface.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

src/gbm/backends/dri/gbm_dri.c

@@ -639,6 +639,30 @@ gbm_dri_is_format_supported(struct gbm_device *gbm,
    return (count > 0);
 }
 
+static int
+gbm_dri_get_format_modifier_plane_count(struct gbm_device *gbm,
+                                        uint32_t format,
+                                        uint64_t modifier)
+{
+   struct gbm_dri_device *dri = gbm_dri_device(gbm);
+   uint64_t plane_count;
+
+   if (dri->image->base.version < 16 ||
+       !dri->image->queryDmaBufFormatModifierAttribs)
+      return -1;
+
+   format = gbm_format_canonicalize(format);
+   if (gbm_format_to_dri_format(format) == 0)
+      return -1;
+
+   if (!dri->image->queryDmaBufFormatModifierAttribs(
+         dri->screen, format, modifier,
+         __DRI_IMAGE_FORMAT_MODIFIER_ATTRIB_PLANE_COUNT, &plane_count))
+      return -1;
+
+   return plane_count;
+}
+
 static int
 gbm_dri_bo_write(struct gbm_bo *_bo, const void *buf, size_t count)
 {
@@ -1350,6 +1374,8 @@ dri_device_create(int fd)
    dri->base.bo_map = gbm_dri_bo_map;
    dri->base.bo_unmap = gbm_dri_bo_unmap;
    dri->base.is_format_supported = gbm_dri_is_format_supported;
+   dri->base.get_format_modifier_plane_count =
+      gbm_dri_get_format_modifier_plane_count;
    dri->base.bo_write = gbm_dri_bo_write;
    dri->base.bo_get_fd = gbm_dri_bo_get_fd;
    dri->base.bo_get_planes = gbm_dri_bo_get_planes;

src/gbm/main/gbm.c

@@ -85,6 +85,20 @@ gbm_device_is_format_supported(struct gbm_device *gbm,
    return gbm->is_format_supported(gbm, format, usage);
 }
 
+/** Get the number of planes that are required for a given format+modifier
+ *
+ * \param gbm The gbm device returned from gbm_create_device()
+ * \param format The format to query
+ * \param modifier The modifier to query
+ */
+GBM_EXPORT int
+gbm_device_get_format_modifier_plane_count(struct gbm_device *gbm,
+                                           uint32_t format,
+                                           uint64_t modifier)
+{
+   return gbm->get_format_modifier_plane_count(gbm, format, modifier);
+}
+
 /** Destroy the gbm device and free all resources associated with it.
  *
  * \param gbm The device created using gbm_create_device()

src/gbm/main/gbm.h

@@ -238,6 +238,11 @@ int
 gbm_device_is_format_supported(struct gbm_device *gbm,
                                uint32_t format, uint32_t usage);
 
+int
+gbm_device_get_format_modifier_plane_count(struct gbm_device *gbm,
+                                           uint32_t format,
+                                           uint64_t modifier);
+
 void
 gbm_device_destroy(struct gbm_device *gbm);
 

src/gbm/main/gbmint.h

@@ -61,6 +61,9 @@ struct gbm_device {
    int (*is_format_supported)(struct gbm_device *gbm,
                               uint32_t format,
                               uint32_t usage);
+   int (*get_format_modifier_plane_count)(struct gbm_device *device,
+                                          uint32_t format,
+                                          uint64_t modifier);
 
    struct gbm_bo *(*bo_create)(struct gbm_device *gbm,
                                uint32_t width, uint32_t height,