[PATCH v2 1/3] drm: add gem ttm helpers

[Gerd Hoffmann <kraxel@redhat.com>]

Now with ttm_buffer_object being a subclass of drm_gem_object we can
easily lookup ttm_buffer_object for a given drm_gem_object, which in
turm allows to create common helper functions.  This patch starts off
with dump mmap helpers.

v2:
 - drop drm_gem_ttm_mmap_offset().
 - improve kerneldocs.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 include/drm/drm_gem_ttm_helper.h     | 27 +++++++++++++++++
 drivers/gpu/drm/drm_gem_ttm_helper.c | 45 ++++++++++++++++++++++++++++
 Documentation/gpu/drm-mm.rst         | 12 ++++++++
 drivers/gpu/drm/Kconfig              |  7 +++++
 drivers/gpu/drm/Makefile             |  3 ++
 5 files changed, 94 insertions(+)
 create mode 100644 include/drm/drm_gem_ttm_helper.h
 create mode 100644 drivers/gpu/drm/drm_gem_ttm_helper.c

diff --git a/include/drm/drm_gem_ttm_helper.h b/include/drm/drm_gem_ttm_helper.h
new file mode 100644
index 000000000000..0c0fbf76af60
--- /dev/null
+++ b/include/drm/drm_gem_ttm_helper.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef DRM_GEM_TTM_HELPER_H
+#define DRM_GEM_TTM_HELPER_H
+
+#include <linux/kernel.h>
+
+#include <drm/drm_gem.h>
+#include <drm/ttm/ttm_bo_api.h>
+
+/**
+ * Returns the container of type &struct ttm_buffer_object
+ * for field base.
+ * @gem:	the GEM object
+ * Returns:	The containing GEM VRAM object
+ */
+static inline struct ttm_buffer_object *drm_gem_ttm_of_gem(
+	struct drm_gem_object *gem)
+{
+	return container_of(gem, struct ttm_buffer_object, base);
+}
+
+int drm_gem_ttm_driver_dumb_mmap_offset(struct drm_file *file,
+					struct drm_device *dev,
+					uint32_t handle, uint64_t *offset);
+
+#endif
diff --git a/drivers/gpu/drm/drm_gem_ttm_helper.c b/drivers/gpu/drm/drm_gem_ttm_helper.c
new file mode 100644
index 000000000000..7aa3c115e42c
--- /dev/null
+++ b/drivers/gpu/drm/drm_gem_ttm_helper.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <drm/drm_gem_ttm_helper.h>
+
+/**
+ * DOC: overview
+ *
+ * This library provides helper functions for gem objects backed by
+ * ttm.
+ */
+
+/**
+ * drm_gem_ttm_driver_dumb_mmap_offset() - \
+	Implements &struct drm_driver.dumb_mmap_offset
+ * @file:	DRM file pointer.
+ * @dev:	DRM device.
+ * @handle:	GEM handle
+ * @offset:	Returns the mapping's memory offset on success
+ *
+ * Returns:
+ * 0 on success, or
+ * a negative errno code otherwise.
+ */
+int drm_gem_ttm_driver_dumb_mmap_offset(struct drm_file *file,
+					 struct drm_device *dev,
+					 uint32_t handle, uint64_t *offset)
+{
+	struct drm_gem_object *gem;
+
+	gem = drm_gem_object_lookup(file, handle);
+	if (!gem)
+		return -ENOENT;
+
+	/*
+	 * No drm_gem_create_mmap_offset() call here, ttm handles this
+	 * at bo initialization time instead.
+	 */
+
+	*offset = drm_vma_node_offset_addr(&gem->vma_node);
+
+	drm_gem_object_put_unlocked(gem);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_gem_ttm_driver_dumb_mmap_offset);
diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst
index b664f054c259..a70a1d9f30ec 100644
--- a/Documentation/gpu/drm-mm.rst
+++ b/Documentation/gpu/drm-mm.rst
@@ -412,6 +412,18 @@ VRAM MM Helper Functions Reference
 .. kernel-doc:: drivers/gpu/drm/drm_vram_mm_helper.c
    :export:
 
+GEM TTM Helper Functions Reference
+-----------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_gem_ttm_helper.c
+   :doc: overview
+
+.. kernel-doc:: include/drm/drm_gem_ttm_helper.h
+   :internal:
+
+.. kernel-doc:: drivers/gpu/drm/drm_gem_ttm_helper.c
+   :export:
+
 VMA Offset Manager
 ==================
 
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index e6f40fb54c9a..f7b25519f95c 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -172,6 +172,13 @@ config DRM_VRAM_HELPER
 	help
 	  Helpers for VRAM memory management
 
+config DRM_TTM_HELPER
+	tristate
+	depends on DRM
+	select DRM_TTM
+	help
+	  Helpers for ttm-based gem objects
+
 config DRM_GEM_CMA_HELPER
 	bool
 	depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 10f8329a8b71..545c61d6528b 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -37,6 +37,9 @@ drm_vram_helper-y := drm_gem_vram_helper.o \
 		     drm_vram_mm_helper.o
 obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
 
+drm_ttm_helper-y := drm_gem_ttm_helper.o
+obj-$(CONFIG_DRM_TTM_HELPER) += drm_ttm_helper.o
+
 drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o drm_probe_helper.o \
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
 		drm_kms_helper_common.o drm_dp_dual_mode_helper.o \
-- 
2.18.1