xf86drmMode: add helpers for dumb buffers

Up until now, DRM clients had to hand-roll their code to create,
destroy and map dumb buffers. This is slightly inconvenient,
a bit error-prone, and not easily discoverable.

Introduce wrappers for these operations, just like we have for
other KMS IOCTLs.

Signed-off-by: Simon Ser <contact@emersion.fr>

core-symbols.txt

@@ -105,10 +105,12 @@ drmModeAtomicSetCursor
 drmModeAttachMode
 drmModeConnectorGetPossibleCrtcs
 drmModeConnectorSetProperty
+drmModeCreateDumbBuffer
 drmModeCreateLease
 drmModeCreatePropertyBlob
 drmModeCrtcGetGamma
 drmModeCrtcSetGamma
+drmModeDestroyDumbBuffer
 drmModeDestroyPropertyBlob
 drmModeDetachMode
 drmModeDirtyFB
@@ -139,6 +141,7 @@ drmModeGetProperty
 drmModeGetPropertyBlob
 drmModeGetResources
 drmModeListLessees
+drmModeMapDumbBuffer
 drmModeMoveCursor
 drmModeObjectGetProperties
 drmModeObjectSetProperty

xf86drmMode.c

@@ -1823,3 +1823,52 @@ drmModeGetConnectorTypeName(uint32_t connector_type)
 		return NULL;
 	}
 }
+
+drm_public int
+drmModeCreateDumbBuffer(int fd, uint32_t width, uint32_t height, uint32_t bpp,
+                        uint32_t flags, uint32_t *handle, uint32_t *pitch,
+                        uint64_t *size)
+{
+	int ret;
+	struct drm_mode_create_dumb create = {
+		.width = width,
+		.height = height,
+		.bpp = bpp,
+		.flags = flags,
+	};
+
+	ret = DRM_IOCTL(fd, DRM_IOCTL_MODE_CREATE_DUMB, &create);
+	if (ret != 0)
+		return ret;
+
+	*handle = create.handle;
+	*pitch = create.pitch;
+	*size = create.size;
+	return 0;
+}
+
+drm_public int
+drmModeDestroyDumbBuffer(int fd, uint32_t handle)
+{
+	struct drm_mode_destroy_dumb destroy = {
+		.handle = handle,
+	};
+
+	return DRM_IOCTL(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroy);
+}
+
+drm_public int
+drmModeMapDumbBuffer(int fd, uint32_t handle, uint64_t *offset)
+{
+	int ret;
+	struct drm_mode_map_dumb map = {
+		.handle = handle,
+	};
+
+	ret = DRM_IOCTL(fd, DRM_IOCTL_MODE_MAP_DUMB, &map);
+	if (ret != 0)
+		return ret;
+
+	*offset = map.offset;
+	return 0;
+}

xf86drmMode.h

@@ -497,6 +497,38 @@ extern int drmModeRevokeLease(int fd, uint32_t lessee_id);
 extern const char *
 drmModeGetConnectorTypeName(uint32_t connector_type);
 
+/**
+ * Create a dumb buffer.
+ *
+ * Given a width, height and bits-per-pixel, the kernel will return a buffer
+ * handle, pitch and size. The flags must be zero.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+extern int
+drmModeCreateDumbBuffer(int fd, uint32_t width, uint32_t height, uint32_t bpp,
+                        uint32_t flags, uint32_t *handle, uint32_t *pitch,
+                        uint64_t *size);
+
+/**
+ * Destroy a dumb buffer.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+extern int
+drmModeDestroyDumbBuffer(int fd, uint32_t handle);
+
+/**
+ * Prepare a dumb buffer for mapping.
+ *
+ * The kernel returns an offset which can be used as an argument to mmap(2) on
+ * the DRM FD.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+extern int
+drmModeMapDumbBuffer(int fd, uint32_t handle, uint64_t *offset);
+
 #if defined(__cplusplus)
 }
 #endif