/*
 * 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 <drm/drmP.h>

/*
 * DMA-BUF/GEM Object references and lifetime overview:
 *
 * On the export the dma_buf holds a reference to the exporting GEM
 * object. It takes this reference in handle_to_fd_ioctl, when it
 * first calls .prime_export and stores the exporting GEM object in
 * the dma_buf priv. This reference is released when the dma_buf
 * object goes away in the driver .release function.
 *
 * On the import the importing GEM object holds a reference to the
 * dma_buf (which in turn holds a ref to the exporting GEM object).
 * It takes that reference in the fd_to_handle ioctl.
 * It calls dma_buf_get, creates an attachment to it and stores the
 * attachment in the GEM object. When this attachment is destroyed
 * when the imported object is destroyed, we remove the attachment
 * and drop the reference to the dma_buf.
 *
 * Thus the chain of references always flows in one direction
 * (avoiding loops): importing_gem -> dmabuf -> exporting_gem
 *
 * 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 gem object
 * from the dma-buf private.
 */

struct drm_prime_member {
        struct list_head entry;
        struct dma_buf *dma_buf;
        uint32_t handle;
};

int drm_gem_prime_handle_to_fd(struct drm_device *dev,
                struct drm_file *file_priv, uint32_t handle, uint32_t flags,
                int *prime_fd)
{
        struct drm_gem_object *obj;
        void *buf;
        int ret;

        obj = drm_gem_object_lookup(dev, file_priv, handle);
        if (!obj)
                return -ENOENT;

        mutex_lock(&file_priv->prime.lock);
        /* re-export the original imported object */
        if (obj->import_attach) {
                get_dma_buf(obj->import_attach->dmabuf);
                *prime_fd = dma_buf_fd(obj->import_attach->dmabuf, flags);
                drm_gem_object_unreference_unlocked(obj);
                mutex_unlock(&file_priv->prime.lock);
                return 0;
        }

        if (obj->export_dma_buf) {
                get_dma_buf(obj->export_dma_buf);
                *prime_fd = dma_buf_fd(obj->export_dma_buf, flags);
                drm_gem_object_unreference_unlocked(obj);
        } else {
                buf = dev->driver->gem_prime_export(dev, obj, flags);
                if (IS_ERR(buf)) {
                        /* normally the created dma-buf takes ownership of the ref,
                         * but if that fails then drop the ref
                         */
                        drm_gem_object_unreference_unlocked(obj);
                        mutex_unlock(&file_priv->prime.lock);
                        return PTR_ERR(buf);
                }
                obj->export_dma_buf = buf;
                *prime_fd = dma_buf_fd(buf, flags);
        }
        /* if we've exported this buffer the cheat and add it to the import list
         * so we get the correct handle back
         */
        ret = drm_prime_add_imported_buf_handle(&file_priv->prime,
                        obj->export_dma_buf, handle);
        if (ret) {
                drm_gem_object_unreference_unlocked(obj);
                mutex_unlock(&file_priv->prime.lock);
                return ret;
        }

        mutex_unlock(&file_priv->prime.lock);
        return 0;
}
EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);

int drm_gem_prime_fd_to_handle(struct drm_device *dev,
                struct drm_file *file_priv, int prime_fd, uint32_t *handle)
{
        struct dma_buf *dma_buf;
        struct drm_gem_object *obj;
        int ret;

        dma_buf = dma_buf_get(prime_fd);
        if (IS_ERR(dma_buf))
                return PTR_ERR(dma_buf);

        mutex_lock(&file_priv->prime.lock);

        ret = drm_prime_lookup_imported_buf_handle(&file_priv->prime,
                        dma_buf, handle);
        if (!ret) {
                ret = 0;
                goto out_put;
        }

        /* never seen this one, need to import */
        obj = dev->driver->gem_prime_import(dev, dma_buf);
        if (IS_ERR(obj)) {
                ret = PTR_ERR(obj);
                goto out_put;
        }

        ret = drm_gem_handle_create(file_priv, obj, handle);
        drm_gem_object_unreference_unlocked(obj);
        if (ret)
                goto out_put;

        ret = drm_prime_add_imported_buf_handle(&file_priv->prime,
                        dma_buf, *handle);
        if (ret)
                goto fail;

        mutex_unlock(&file_priv->prime.lock);
        return 0;

fail:
        /* hmm, if driver attached, we are relying on the free-object path
         * to detach.. which seems ok..
         */
        drm_gem_object_handle_unreference_unlocked(obj);
out_put:
        dma_buf_put(dma_buf);
        mutex_unlock(&file_priv->prime.lock);
        return ret;
}
EXPORT_SYMBOL(drm_gem_prime_fd_to_handle);

int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data,
                                 struct drm_file *file_priv)
{
        struct drm_prime_handle *args = data;
        uint32_t flags;

        if (!drm_core_check_feature(dev, DRIVER_PRIME))
                return -EINVAL;

        if (!dev->driver->prime_handle_to_fd)
                return -ENOSYS;

        /* check flags are valid */
        if (args->flags & ~DRM_CLOEXEC)
                return -EINVAL;

        /* we only want to pass DRM_CLOEXEC which is == O_CLOEXEC */
        flags = args->flags & DRM_CLOEXEC;

        return dev->driver->prime_handle_to_fd(dev, file_priv,
                        args->handle, flags, &args->fd);
}

int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data,
                                 struct drm_file *file_priv)
{
        struct drm_prime_handle *args = data;

        if (!drm_core_check_feature(dev, DRIVER_PRIME))
                return -EINVAL;

        if (!dev->driver->prime_fd_to_handle)
                return -ENOSYS;

        return dev->driver->prime_fd_to_handle(dev, file_priv,
                        args->fd, &args->handle);
}

/*
 * drm_prime_pages_to_sg
 *
 * this helper creates an sg table object from a set of pages
 * the driver is responsible for mapping the pages into the
 * importers address space
 */
struct sg_table *drm_prime_pages_to_sg(struct page **pages, int nr_pages)
{
        struct sg_table *sg = NULL;
        struct scatterlist *iter;
        int i;
        int ret;

        sg = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
        if (!sg)
                goto out;

        ret = sg_alloc_table(sg, nr_pages, GFP_KERNEL);
        if (ret)
                goto out;

        for_each_sg(sg->sgl, iter, nr_pages, i)
                sg_set_page(iter, pages[i], PAGE_SIZE, 0);

        return sg;
out:
        kfree(sg);
        return NULL;
}
EXPORT_SYMBOL(drm_prime_pages_to_sg);

/* export an sg table into an array of pages and addresses
   this is currently required by the TTM driver in order to do correct fault
   handling */
int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
                                     dma_addr_t *addrs, int max_pages)
{
        unsigned count;
        struct scatterlist *sg;
        struct page *page;
        u32 len, offset;
        int pg_index;
        dma_addr_t addr;

        pg_index = 0;
        for_each_sg(sgt->sgl, sg, sgt->nents, count) {
                len = sg->length;
                offset = sg->offset;
                page = sg_page(sg);
                addr = sg_dma_address(sg);

                while (len > 0) {
                        if (WARN_ON(pg_index >= max_pages))
                                return -1;
                        pages[pg_index] = page;
                        if (addrs)
                                addrs[pg_index] = addr;

                        page++;
                        addr += PAGE_SIZE;
                        len -= PAGE_SIZE;
                        pg_index++;
                }
        }
        return 0;
}
EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
/* helper function to cleanup a GEM/prime object */
void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg)
{
        struct dma_buf_attachment *attach;
        struct dma_buf *dma_buf;
        attach = obj->import_attach;
        if (sg)
                dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
        dma_buf = attach->dmabuf;
        dma_buf_detach(attach->dmabuf, attach);
        /* remove the reference */
        dma_buf_put(dma_buf);
}
EXPORT_SYMBOL(drm_prime_gem_destroy);

void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv)
{
        INIT_LIST_HEAD(&prime_fpriv->head);
        mutex_init(&prime_fpriv->lock);
}
EXPORT_SYMBOL(drm_prime_init_file_private);

void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv)
{
        struct drm_prime_member *member, *safe;
        list_for_each_entry_safe(member, safe, &prime_fpriv->head, entry) {
                list_del(&member->entry);
                kfree(member);
        }
}
EXPORT_SYMBOL(drm_prime_destroy_file_private);

int drm_prime_add_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle)
{
        struct drm_prime_member *member;

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

        member->dma_buf = dma_buf;
        member->handle = handle;
        list_add(&member->entry, &prime_fpriv->head);
        return 0;
}
EXPORT_SYMBOL(drm_prime_add_imported_buf_handle);

int drm_prime_lookup_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t *handle)
{
        struct drm_prime_member *member;

        list_for_each_entry(member, &prime_fpriv->head, entry) {
                if (member->dma_buf == dma_buf) {
                        *handle = member->handle;
                        return 0;
                }
        }
        return -ENOENT;
}
EXPORT_SYMBOL(drm_prime_lookup_imported_buf_handle);

void drm_prime_remove_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf)
{
        struct drm_prime_member *member, *safe;

        mutex_lock(&prime_fpriv->lock);
        list_for_each_entry_safe(member, safe, &prime_fpriv->head, entry) {
                if (member->dma_buf == dma_buf) {
                        list_del(&member->entry);
                        kfree(member);
                }
        }
        mutex_unlock(&prime_fpriv->lock);
}
EXPORT_SYMBOL(drm_prime_remove_imported_buf_handle);