path: root/drivers/gpu/drm/drm_prime.c

/*
 * Copyright © 2012 Red Hat
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *      Dave Airlie <airlied@redhat.com>
 *      Rob Clark <rob.clark@linaro.org>
 *
 */

#include <linux/export.h>
#include <linux/dma-buf.h>
#include <linux/rbtree.h>
#include <linux/module.h>

#include <drm/drm.h>
#include <drm/drm_drv.h>
#include <drm/drm_file.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem.h>
#include <drm/drm_prime.h>
#include <drm/drm_print.h>

#include "drm_internal.h"

MODULE_IMPORT_NS("DMA_BUF");

/**
 * DOC: overview and lifetime rules
 *
 * Similar to GEM global names, PRIME file descriptors are also used to share
 * buffer objects across processes. They offer additional security: as file
 * descriptors must be explicitly sent over UNIX domain sockets to be shared
 * between applications, they can't be guessed like the globally unique GEM
 * names.
 *
 * Drivers that support the PRIME API implement the drm_gem_object_funcs.export
 * and &drm_driver.gem_prime_import hooks. &dma_buf_ops implementations for
 * drivers are all individually exported for drivers which need to overwrite
 * or reimplement some of them.
 *
 * Reference Counting for GEM Drivers
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 * On the export the &dma_buf holds a reference to the exported buffer object,
 * usually a &drm_gem_object. It takes this reference in the PRIME_HANDLE_TO_FD
 * IOCTL, when it first calls &drm_gem_object_funcs.export
 * and stores the exporting GEM object in the &dma_buf.priv field. This
 * reference needs to be released when the final reference to the &dma_buf
 * itself is dropped and its &dma_buf_ops.release function is called.  For
 * GEM-based drivers, the &dma_buf should be exported using
 * drm_gem_dmabuf_export() and then released by drm_gem_dmabuf_release().
 *
 * Thus the chain of references always flows in one direction, avoiding loops:
 * importing GEM object -> dma-buf -> exported GEM bo. A further complication
 * are the lookup caches for import and export. These are required to guarantee
 * that any given object will always have only one unique userspace handle. This
 * is required to allow userspace to detect duplicated imports, since some GEM
 * drivers do fail command submissions if a given buffer object is listed more
 * than once. These import and export caches in &drm_prime_file_private only
 * retain a weak reference, which is cleaned up when the corresponding object is
 * released.
 *
 * Self-importing: If userspace is using PRIME as a replacement for flink then
 * it will get a fd->handle request for a GEM object that it created.  Drivers
 * should detect this situation and return back the underlying object from the
 * dma-buf private. For GEM based drivers this is handled in
 * drm_gem_prime_import() already.
 */

struct drm_prime_member {
	struct dma_buf *dma_buf;
	uint32_t handle;

	struct rb_node dmabuf_rb;
	struct rb_node handle_rb;
};

int drm_prime_add_buf_handle(struct drm_prime_file_private *prime_fpriv,
				    struct dma_buf *dma_buf, uint32_t handle)
{
	struct drm_prime_member *member;
	struct rb_node **p, *rb;

	member = kmalloc(sizeof(*member), GFP_KERNEL);
	if (!member)
		return -ENOMEM;

	get_dma_buf(dma_buf);
	member->dma_buf = dma_buf;
	member->handle = handle;

	rb = NULL;
	p = &prime_fpriv->dmabufs.rb_node;
	while (*p) {
		struct drm_prime_member *pos;

		rb = *p;
		pos = rb_entry(rb, struct drm_prime_member, dmabuf_rb);
		if (dma_buf > pos->dma_buf)
			p = &rb->rb_right;
		else
			p = &rb->rb_left;
	}
	rb_link_node(&member->dmabuf_rb, rb, p);
	rb_insert_color(&member->dmabuf_rb, &prime_fpriv->dmabufs);

	rb = NULL;
	p = &prime_fpriv->handles.rb_node;
	while (*p) {
		struct drm_prime_member *pos;

		rb = *p;
		pos = rb_entry(rb, struct drm_prime_member, handle_rb);
		if (handle > pos->handle)
			p = &rb->rb_right;
		else
			p = &rb->rb_left;
	}
	rb_link_node(&member->handle_rb, rb, p);
	rb_insert_color(&member->handle_rb, &prime_fpriv->handles);

	return 0;
}

static struct dma_buf *drm_prime_lookup_buf_by_handle(struct drm_prime_file_private *prime_fpriv,
						      uint32_t handle)
{
	struct rb_node *rb;

	rb = prime_fpriv->handles.rb_node;