drm: Add VRAM MM, a simple memory manager for dedicated VRAM

The VRAM MM memory manager is a helper library that manages dedicated video
memory of simple framebuffer devices. It is supported to be used with
struct drm_gem_vram_object, but does not depend on it.

The implementation is based on the respective code from ast, bochs, and
mgag200. These drivers share the exact same implementation except for type
names. The helpers are currently build with TTM. This may change in future
revisions.

v4:
	* cleanups from checkpatch.pl
v2:
	* renamed to struct drm_vram_mm
	* add drm_vram_mm_mmap() helper
	* documentation fixes

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190508082630.15116-7-tzimmermann@suse.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/include/drm/drm_vram_mm_helper.h b/include/drm/drm_vram_mm_helper.h
new file mode 100644
index 000000000000..5d45c6447fa4
--- /dev/null
+++ b/include/drm/drm_vram_mm_helper.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef DRM_VRAM_MM_HELPER_H
+#define DRM_VRAM_MM_HELPER_H
+
+#include <drm/ttm/ttm_bo_driver.h>
+
+struct drm_device;
+
+/**
+ * struct drm_vram_mm_funcs - Callback functions for &struct drm_vram_mm
+ * @evict_flags:	Provides an implementation for struct \
+	&ttm_bo_driver.evict_flags
+ * @verify_access:	Provides an implementation for \
+	struct &ttm_bo_driver.verify_access
+ *
+ * These callback function integrate VRAM MM with TTM buffer objects. New
+ * functions can be added if necessary.
+ */
+struct drm_vram_mm_funcs {
+	void (*evict_flags)(struct ttm_buffer_object *bo,
+			    struct ttm_placement *placement);
+	int (*verify_access)(struct ttm_buffer_object *bo, struct file *filp);
+};
+
+/**
+ * struct drm_vram_mm - An instance of VRAM MM
+ * @vram_base:	Base address of the managed video memory
+ * @vram_size:	Size of the managed video memory in bytes
+ * @bdev:	The TTM BO device.
+ * @funcs:	TTM BO functions
+ *
+ * The fields &struct drm_vram_mm.vram_base and
+ * &struct drm_vram_mm.vrm_size are managed by VRAM MM, but are
+ * available for public read access. Use the field
+ * &struct drm_vram_mm.bdev to access the TTM BO device.
+ */
+struct drm_vram_mm {
+	uint64_t vram_base;
+	size_t vram_size;
+
+	struct ttm_bo_device bdev;
+
+	const struct drm_vram_mm_funcs *funcs;
+};
+
+/**
+ * drm_vram_mm_of_bdev() - \
+	Returns the container of type &struct ttm_bo_device for field bdev.
+ * @bdev:	the TTM BO device
+ *
+ * Returns:
+ * The containing instance of &struct drm_vram_mm
+ */
+static inline struct drm_vram_mm *drm_vram_mm_of_bdev(
+	struct ttm_bo_device *bdev)
+{
+	return container_of(bdev, struct drm_vram_mm, bdev);
+}
+
+int drm_vram_mm_init(struct drm_vram_mm *vmm, struct drm_device *dev,
+		     uint64_t vram_base, size_t vram_size,
+		     const struct drm_vram_mm_funcs *funcs);
+void drm_vram_mm_cleanup(struct drm_vram_mm *vmm);
+
+int drm_vram_mm_mmap(struct file *filp, struct vm_area_struct *vma,
+		     struct drm_vram_mm *vmm);
+
+#endif