drm: Add GEM backed framebuffer library

This library provides helpers for drivers that don't subclass
drm_framebuffer and are backed by drm_gem_object. The code is
taken from drm_fb_cma_helper.
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/1502631125-13557-2-git-send-email-noralf@tronnes.org

Documentation/gpu/drm-kms-helpers.rst

@@ -296,3 +296,12 @@ Auxiliary Modeset Helpers
 
 .. kernel-doc:: drivers/gpu/drm/drm_modeset_helper.c
    :export:
+
+Framebuffer GEM Helper Reference
+================================
+
+.. kernel-doc:: drivers/gpu/drm/drm_gem_framebuffer_helper.c
+   :doc: overview
+
+.. kernel-doc:: drivers/gpu/drm/drm_gem_framebuffer_helper.c
+   :export:

drivers/gpu/drm/Makefile

@@ -33,7 +33,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.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 \
 		drm_simple_kms_helper.o drm_modeset_helper.o \
-		drm_scdc_helper.o
+		drm_scdc_helper.o drm_gem_framebuffer_helper.o
 
 drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
 drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o

drivers/gpu/drm/drm_gem_framebuffer_helper.c

+/*
+ * drm gem framebuffer helper functions
+ *
+ * Copyright (C) 2017 Noralf Trønnes
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/dma-fence.h>
+#include <linux/reservation.h>
+#include <linux/slab.h>
+
+#include <drm/drmP.h>
+#include <drm/drm_atomic.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_modeset_helper.h>
+
+/**
+ * DOC: overview
+ *
+ * This library provides helpers for drivers that don't subclass
+ * &drm_framebuffer and and use &drm_gem_object for their backing storage.
+ *
+ * Drivers without additional needs to validate framebuffers can simply use
+ * drm_gem_fb_create() and everything is wired up automatically. But all
+ * parts can be used individually.
+ */
+
+/**
+ * drm_gem_fb_get_obj() - Get GEM object for framebuffer
+ * @fb: The framebuffer
+ * @plane: Which plane
+ *
+ * Returns the GEM object for given framebuffer.
+ */
+struct drm_gem_object *drm_gem_fb_get_obj(struct drm_framebuffer *fb,
+					  unsigned int plane)
+{
+	if (plane >= 4)
+		return NULL;
+
+	return fb->obj[plane];
+}
+EXPORT_SYMBOL_GPL(drm_gem_fb_get_obj);
+
+static struct drm_framebuffer *
+drm_gem_fb_alloc(struct drm_device *dev,
+		 const struct drm_mode_fb_cmd2 *mode_cmd,
+		 struct drm_gem_object **obj, unsigned int num_planes,
+		 const struct drm_framebuffer_funcs *funcs)
+{
+	struct drm_framebuffer *fb;
+	int ret, i;
+
+	fb = kzalloc(sizeof(*fb), GFP_KERNEL);
+	if (!fb)
+		return ERR_PTR(-ENOMEM);
+
+	drm_helper_mode_fill_fb_struct(dev, fb, mode_cmd);
+
+	for (i = 0; i < num_planes; i++)
+		fb->obj[i] = obj[i];
+
+	ret = drm_framebuffer_init(dev, fb, funcs);
+	if (ret) {
+		DRM_DEV_ERROR(dev->dev, "Failed to init framebuffer: %d\n",
+			      ret);
+		kfree(fb);
+		return ERR_PTR(ret);
+	}
+
+	return fb;
+}
+
+/**
+ * drm_gem_fb_destroy - Free GEM backed framebuffer
+ * @fb: DRM framebuffer
+ *
+ * Frees a GEM backed framebuffer with its backing buffer(s) and the structure
+ * itself. Drivers can use this as their &drm_framebuffer_funcs->destroy
+ * callback.
+ */
+void drm_gem_fb_destroy(struct drm_framebuffer *fb)
+{
+	int i;
+
+	for (i = 0; i < 4; i++)
+		drm_gem_object_put_unlocked(fb->obj[i]);
+
+	drm_framebuffer_cleanup(fb);
+	kfree(fb);
+}
+EXPORT_SYMBOL(drm_gem_fb_destroy);
+
+/**
+ * drm_gem_fb_create_handle - Create handle for GEM backed framebuffer
+ * @fb: DRM framebuffer
+ * @file: drm file
+ * @handle: handle created
+ *
+ * Drivers can use this as their &drm_framebuffer_funcs->create_handle
+ * callback.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_fb_create_handle(struct drm_framebuffer *fb, struct drm_file *file,
+			     unsigned int *handle)
+{
+	return drm_gem_handle_create(file, fb->obj[0], handle);
+}
+EXPORT_SYMBOL(drm_gem_fb_create_handle);
+
+/**
+ * drm_gem_fb_create_with_funcs() - helper function for the
+ *                                  &drm_mode_config_funcs.fb_create
+ *                                  callback
+ * @dev: DRM device
+ * @file: drm file for the ioctl call
+ * @mode_cmd: metadata from the userspace fb creation request
+ * @funcs: vtable to be used for the new framebuffer object
+ *
+ * This can be used to set &drm_framebuffer_funcs for drivers that need the
+ * &drm_framebuffer_funcs.dirty callback. Use drm_gem_fb_create() if you don't
+ * need to change &drm_framebuffer_funcs.
+ * The function does buffer size validation.
+ */
+struct drm_framebuffer *
+drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
+			     const struct drm_mode_fb_cmd2 *mode_cmd,
+			     const struct drm_framebuffer_funcs *funcs)
+{
+	const struct drm_format_info *info;
+	struct drm_gem_object *objs[4];
+	struct drm_framebuffer *fb;
+	int ret, i;
+
+	info = drm_get_format_info(dev, mode_cmd);
+	if (!info)
+		return ERR_PTR(-EINVAL);
+
+	for (i = 0; i < info->num_planes; i++) {
+		unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
+		unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
+		unsigned int min_size;
+
+		objs[i] = drm_gem_object_lookup(file, mode_cmd->handles[i]);
+		if (!objs[i]) {
+			DRM_DEV_ERROR(dev->dev, "Failed to lookup GEM\n");
+			ret = -ENOENT;
+			goto err_gem_object_put;
+		}
+
+		min_size = (height - 1) * mode_cmd->pitches[i]
+			 + width * info->cpp[i]
+			 + mode_cmd->offsets[i];
+
+		if (objs[i]->size < min_size) {
+			drm_gem_object_put_unlocked(objs[i]);
+			ret = -EINVAL;
+			goto err_gem_object_put;
+		}
+	}
+
+	fb = drm_gem_fb_alloc(dev, mode_cmd, objs, i, funcs);
+	if (IS_ERR(fb)) {
+		ret = PTR_ERR(fb);
+		goto err_gem_object_put;
+	}
+
+	return fb;
+
+err_gem_object_put:
+	for (i--; i >= 0; i--)
+		drm_gem_object_put_unlocked(objs[i]);
+
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(drm_gem_fb_create_with_funcs);
+
+static const struct drm_framebuffer_funcs drm_gem_fb_funcs = {
+	.destroy	= drm_gem_fb_destroy,
+	.create_handle	= drm_gem_fb_create_handle,
+};
+
+/**
+ * drm_gem_fb_create() - &drm_mode_config_funcs.fb_create callback function
+ * @dev: DRM device
+ * @file: drm file for the ioctl call
+ * @mode_cmd: metadata from the userspace fb creation request
+ *
+ * If your hardware has special alignment or pitch requirements these should be
+ * checked before calling this function. The function does buffer size
+ * validation. Use drm_gem_fb_create_with_funcs() if you need to set
+ * &drm_framebuffer_funcs.dirty.
+ */
+struct drm_framebuffer *
+drm_gem_fb_create(struct drm_device *dev, struct drm_file *file,
+		  const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
+					    &drm_gem_fb_funcs);
+}
+EXPORT_SYMBOL_GPL(drm_gem_fb_create);
+
+/**
+ * drm_gem_fb_prepare_fb() - Prepare gem framebuffer
+ * @plane: Which plane
+ * @state: Plane state attach fence to
+ *
+ * This can be used as the &drm_plane_helper_funcs.prepare_fb hook.
+ *
+ * This function checks if the plane FB has an dma-buf attached, extracts
+ * the exclusive fence and attaches it to plane state for the atomic helper
+ * to wait on.
+ *
+ * There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple
+ * gem based framebuffer drivers which have their buffers always pinned in
+ * memory.
+ */
+int drm_gem_fb_prepare_fb(struct drm_plane *plane,
+			  struct drm_plane_state *state)
+{
+	struct dma_buf *dma_buf;
+	struct dma_fence *fence;
+
+	if ((plane->state->fb == state->fb) || !state->fb)
+		return 0;
+
+	dma_buf = drm_gem_fb_get_obj(state->fb, 0)->dma_buf;
+	if (dma_buf) {
+		fence = reservation_object_get_excl_rcu(dma_buf->resv);
+		drm_atomic_set_fence_for_plane(state, fence);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_fb_prepare_fb);
+
+/**
+ * drm_gem_fbdev_fb_create - Create a drm_framebuffer for fbdev emulation
+ * @dev: DRM device
+ * @sizes: fbdev size description
+ * @pitch_align: optional pitch alignment
+ * @obj: GEM object backing the framebuffer
+ * @funcs: vtable to be used for the new framebuffer object
+ *
+ * This function creates a framebuffer for use with fbdev emulation.
+ *
+ * Returns:
+ * Pointer to a drm_framebuffer on success or an error pointer on failure.
+ */
+struct drm_framebuffer *
+drm_gem_fbdev_fb_create(struct drm_device *dev,
+			struct drm_fb_helper_surface_size *sizes,
+			unsigned int pitch_align, struct drm_gem_object *obj,
+			const struct drm_framebuffer_funcs *funcs)
+{
+	struct drm_mode_fb_cmd2 mode_cmd = { 0 };
+
+	mode_cmd.width = sizes->surface_width;
+	mode_cmd.height = sizes->surface_height;
+	mode_cmd.pitches[0] = sizes->surface_width *
+			      DIV_ROUND_UP(sizes->surface_bpp, 8);
+	if (pitch_align)
+		mode_cmd.pitches[0] = roundup(mode_cmd.pitches[0],
+					      pitch_align);
+	mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
+							sizes->surface_depth);
+	if (obj->size < mode_cmd.pitches[0] * mode_cmd.height)
+		return ERR_PTR(-EINVAL);
+
+	return drm_gem_fb_alloc(dev, &mode_cmd, &obj, 1, funcs);
+}
+EXPORT_SYMBOL(drm_gem_fbdev_fb_create);

include/drm/drm_framebuffer.h

@@ -190,6 +190,13 @@ struct drm_framebuffer {
 	 * @filp_head: Placed on &drm_file.fbs, protected by &drm_file.fbs_lock.
 	 */
 	struct list_head filp_head;
+	/**
+	 * @obj: GEM objects backing the framebuffer, one per plane (optional).
+	 *
+	 * This is used by the GEM framebuffer helpers, see e.g.
+	 * drm_gem_fb_create().
+	 */
+	struct drm_gem_object *obj[4];
 };
 
 #define obj_to_fb(x) container_of(x, struct drm_framebuffer, base)

include/drm/drm_gem_framebuffer_helper.h

+#ifndef __DRM_GEM_FB_HELPER_H__
+#define __DRM_GEM_FB_HELPER_H__
+
+struct drm_device;
+struct drm_file;
+struct drm_fb_helper_surface_size;
+struct drm_framebuffer;
+struct drm_framebuffer_funcs;
+struct drm_gem_object;
+struct drm_mode_fb_cmd2;
+struct drm_plane;
+struct drm_plane_state;
+
+struct drm_gem_object *drm_gem_fb_get_obj(struct drm_framebuffer *fb,
+					  unsigned int plane);
+void drm_gem_fb_destroy(struct drm_framebuffer *fb);
+int drm_gem_fb_create_handle(struct drm_framebuffer *fb, struct drm_file *file,
+			     unsigned int *handle);
+
+struct drm_framebuffer *
+drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
+			     const struct drm_mode_fb_cmd2 *mode_cmd,
+			     const struct drm_framebuffer_funcs *funcs);
+struct drm_framebuffer *
+drm_gem_fb_create(struct drm_device *dev, struct drm_file *file,
+		  const struct drm_mode_fb_cmd2 *mode_cmd);
+
+int drm_gem_fb_prepare_fb(struct drm_plane *plane,
+			  struct drm_plane_state *state);
+
+struct drm_framebuffer *
+drm_gem_fbdev_fb_create(struct drm_device *dev,
+			struct drm_fb_helper_surface_size *sizes,
+			unsigned int pitch_align, struct drm_gem_object *obj,
+			const struct drm_framebuffer_funcs *funcs);
+
+#endif