/*
 * Framework for buffer objects that can be shared across devices/subsystems.
 *
 * Copyright(C) 2011 Linaro Limited. All rights reserved.
 * Author: Sumit Semwal <sumit.semwal@ti.com>
 *
 * Many thanks to linaro-mm-sig list, and specially
 * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
 * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
 * refining of this idea.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/dma-buf.h>
#include <linux/anon_inodes.h>
#include <linux/export.h>

static inline int is_dma_buf_file(struct file *);

static int dma_buf_release(struct inode *inode, struct file *file)
{
        struct dma_buf *dmabuf;

        if (!is_dma_buf_file(file))
                return -EINVAL;

        dmabuf = file->private_data;

        dmabuf->ops->release(dmabuf);
        kfree(dmabuf);
        return 0;
}

static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
{
        struct dma_buf *dmabuf;

        if (!is_dma_buf_file(file))
                return -EINVAL;

        dmabuf = file->private_data;

        /* check for overflowing the buffer's size */
        if (vma->vm_pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) >
            dmabuf->size >> PAGE_SHIFT)
                return -EINVAL;

        return dmabuf->ops->mmap(dmabuf, vma);
}

static const struct file_operations dma_buf_fops = {
        .release        = dma_buf_release,
        .mmap           = dma_buf_mmap_internal,
};

/*
 * is_dma_buf_file - Check if struct file* is associated with dma_buf
 */
static inline int is_dma_buf_file(struct file *file)
{
        return file->f_op == &dma_buf_fops;
}

/**
 * dma_buf_export - Creates a new dma_buf, and associates an anon file
 * with this buffer, so it can be exported.
 * Also connect the allocator specific data and ops to the buffer.
 *
 * @priv:       [in]    Attach private data of allocator to this buffer
 * @ops:        [in]    Attach allocator-defined dma buf ops to the new buffer.
 * @size:       [in]    Size of the buffer
 * @flags:      [in]    mode flags for the file.
 *
 * Returns, on success, a newly created dma_buf object, which wraps the
 * supplied private data and operations for dma_buf_ops. On either missing
 * ops, or error in allocating struct dma_buf, will return negative error.
 *
 */
struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
                                size_t size, int flags)
{
        struct dma_buf *dmabuf;
        struct file *file;

        if (WARN_ON(!priv || !ops
                          || !ops->map_dma_buf
                          || !ops->unmap_dma_buf
                          || !ops->release
                          || !ops->kmap_atomic
                          || !ops->kmap
                          || !ops->mmap)) {
                return ERR_PTR(-EINVAL);
        }

        dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);
        if (dmabuf == NULL)
                return ERR_PTR(-ENOMEM);

        dmabuf->priv = priv;
        dmabuf->ops = ops;
        dmabuf->size = size;

        file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);

        dmabuf->file = file;

        mutex_init(&dmabuf->lock);
        INIT_LIST_HEAD(&dmabuf->attachments);

        return dmabuf;
}
EXPORT_SYMBOL_GPL(dma_buf_export);


/**
 * dma_buf_fd - returns a file descriptor for the given dma_buf
 * @dmabuf:     [in]    pointer to dma_buf for which fd is required.
 * @flags:      [in]    flags to give to fd
 *
 * On success, returns an associated 'fd'. Else, returns error.
 */
int dma_buf_fd(struct dma_buf *dmabuf, int flags)
{
        int error, fd;

        if (!dmabuf || !dmabuf->file)
                return -EINVAL;

        error = get_unused_fd_flags(flags);
        if (error < 0)
                return error;
        fd = error;

        fd_install(fd, dmabuf->file);

        return fd;
}
EXPORT_SYMBOL_GPL(dma_buf_fd);

/**
 * dma_buf_get - returns the dma_buf structure related to an fd
 * @fd: [in]    fd associated with the dma_buf to be returned
 *
 * On success, returns the dma_buf structure associated with an fd; uses
 * file's refcounting done by fget to increase refcount. returns ERR_PTR
 * otherwise.
 */
struct dma_buf *dma_buf_get(int fd)
{
        struct file *file;

        file = fget(fd);

        if (!file)
                return ERR_PTR(-EBADF);

        if (!is_dma_buf_file(file)) {
                fput(file);
                return ERR_PTR(-EINVAL);
        }

        return file->private_data;
}
EXPORT_SYMBOL_GPL(dma_buf_get);

/**
 * dma_buf_put - decreases refcount of the buffer
 * @dmabuf:     [in]    buffer to reduce refcount of
 *
 * Uses file's refcounting done implicitly by fput()
 */
void dma_buf_put(struct dma_buf *dmabuf)
{
        if (WARN_ON(!dmabuf || !dmabuf->file))
                return;

        fput(dmabuf->file);
}
EXPORT_SYMBOL_GPL(dma_buf_put);

/**
 * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
 * calls attach() of dma_buf_ops to allow device-specific attach functionality
 * @dmabuf:     [in]    buffer to attach device to.
 * @dev:        [in]    device to be attached.
 *
 * Returns struct dma_buf_attachment * for this attachment; may return negative
 * error codes.
 *
 */
struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
                                          struct device *dev)
{
        struct dma_buf_attachment *attach;
        int ret;

        if (WARN_ON(!dmabuf || !dev))
                return ERR_PTR(-EINVAL);

        attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);
        if (attach == NULL)
                return ERR_PTR(-ENOMEM);

        attach->dev = dev;
        attach->dmabuf = dmabuf;

        mutex_lock(&dmabuf->lock);

        if (dmabuf->ops->attach) {
                ret = dmabuf->ops->attach(dmabuf, dev, attach);
                if (ret)
                        goto err_attach;
        }
        list_add(&attach->node, &dmabuf->attachments);

        mutex_unlock(&dmabuf->lock);
        return attach;

err_attach:
        kfree(attach);
        mutex_unlock(&dmabuf->lock);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dma_buf_attach);

/**
 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
 * optionally calls detach() of dma_buf_ops for device-specific detach
 * @dmabuf:     [in]    buffer to detach from.
 * @attach:     [in]    attachment to be detached; is free'd after this call.
 *
 */
void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
{
        if (WARN_ON(!dmabuf || !attach))
                return;

        mutex_lock(&dmabuf->lock);
        list_del(&attach->node);
        if (dmabuf->ops->detach)
                dmabuf->ops->detach(dmabuf, attach);

        mutex_unlock(&dmabuf->lock);
        kfree(attach);
}
EXPORT_SYMBOL_GPL(dma_buf_detach);

/**
 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
 * dma_buf_ops.
 * @attach:     [in]    attachment whose scatterlist is to be returned
 * @direction:  [in]    direction of DMA transfer
 *
 * Returns sg_table containing the scatterlist to be returned; may return NULL
 * or ERR_PTR.
 *
 */
struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
                                        enum dma_data_direction direction)
{
        struct sg_table *sg_table = ERR_PTR(-EINVAL);

        might_sleep();

        if (WARN_ON(!attach || !attach->dmabuf))
                return ERR_PTR(-EINVAL);

        sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);

        return sg_table;
}
EXPORT_SYMBOL_GPL(dma_buf_map_attachment);

/**
 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
 * dma_buf_ops.
 * @attach:     [in]    attachment to unmap buffer from
 * @sg_table:   [in]    scatterlist info of the buffer to unmap
 * @direction:  [in]    direction of DMA transfer
 *
 */
void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
                                struct sg_table *sg_table,
                                enum dma_data_direction direction)
{
        if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
                return;

        attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
                                                direction);
}
EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);


/**
 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
 * preparations. Coherency is only guaranteed in the specified range for the
 * specified access direction.
 * @dmabuf:     [in]    buffer to prepare cpu access for.
 * @start:      [in]    start of range for cpu access.
 * @len:        [in]    length of range for cpu access.
 * @direction:  [in]    length of range for cpu access.
 *
 * Can return negative error values, returns 0 on success.
 */
int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, size_t start, size_t len,
                             enum dma_data_direction direction)
{
        int ret = 0;

        if (WARN_ON(!dmabuf))
                return -EINVAL;

        if (dmabuf->ops->begin_cpu_access)
                ret = dmabuf->ops->begin_cpu_access(dmabuf, start, len, direction);

        return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);

/**
 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
 * actions. Coherency is only guaranteed in the specified range for the
 * specified access direction.
 * @dmabuf:     [in]    buffer to complete cpu access for.
 * @start:      [in]    start of range for cpu access.
 * @len:        [in]    length of range for cpu access.
 * @direction:  [in]    length of range for cpu access.
 *
 * This call must always succeed.
 */
void dma_buf_end_cpu_access(struct dma_buf *dmabuf, size_t start, size_t len,
                            enum dma_data_direction direction)
{
        WARN_ON(!dmabuf);

        if (dmabuf->ops->end_cpu_access)
                dmabuf->ops->end_cpu_access(dmabuf, start, len, direction);
}
EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);

/**
 * dma_buf_kmap_atomic - Map a page of the buffer object into kernel address
 * space. The same restrictions as for kmap_atomic and friends apply.
 * @dmabuf:     [in]    buffer to map page from.
 * @page_num:   [in]    page in PAGE_SIZE units to map.
 *
 * This call must always succeed, any necessary preparations that might fail
 * need to be done in begin_cpu_access.
 */
void *dma_buf_kmap_atomic(struct dma_buf *dmabuf, unsigned long page_num)
{
        WARN_ON(!dmabuf);

        return dmabuf->ops->kmap_atomic(dmabuf, page_num);
}
EXPORT_SYMBOL_GPL(dma_buf_kmap_atomic);

/**
 * dma_buf_kunmap_atomic - Unmap a page obtained by dma_buf_kmap_atomic.
 * @dmabuf:     [in]    buffer to unmap page from.
 * @page_num:   [in]    page in PAGE_SIZE units to unmap.
 * @vaddr:      [in]    kernel space pointer obtained from dma_buf_kmap_atomic.
 *
 * This call must always succeed.
 */
void dma_buf_kunmap_atomic(struct dma_buf *dmabuf, unsigned long page_num,
                           void *vaddr)
{
        WARN_ON(!dmabuf);

        if (dmabuf->ops->kunmap_atomic)
                dmabuf->ops->kunmap_atomic(dmabuf, page_num, vaddr);
}
EXPORT_SYMBOL_GPL(dma_buf_kunmap_atomic);

/**
 * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
 * same restrictions as for kmap and friends apply.
 * @dmabuf:     [in]    buffer to map page from.
 * @page_num:   [in]    page in PAGE_SIZE units to map.
 *
 * This call must always succeed, any necessary preparations that might fail
 * need to be done in begin_cpu_access.
 */
void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
{
        WARN_ON(!dmabuf);

        return dmabuf->ops->kmap(dmabuf, page_num);
}
EXPORT_SYMBOL_GPL(dma_buf_kmap);

/**
 * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
 * @dmabuf:     [in]    buffer to unmap page from.
 * @page_num:   [in]    page in PAGE_SIZE units to unmap.
 * @vaddr:      [in]    kernel space pointer obtained from dma_buf_kmap.
 *
 * This call must always succeed.
 */
void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
                    void *vaddr)
{
        WARN_ON(!dmabuf);

        if (dmabuf->ops->kunmap)
                dmabuf->ops->kunmap(dmabuf, page_num, vaddr);
}
EXPORT_SYMBOL_GPL(dma_buf_kunmap);


/**
 * dma_buf_mmap - Setup up a userspace mmap with the given vma
 * @dmabuf:     [in]    buffer that should back the vma
 * @vma:        [in]    vma for the mmap
 * @pgoff:      [in]    offset in pages where this mmap should start within the
 *                      dma-buf buffer.
 *
 * This function adjusts the passed in vma so that it points at the file of the
 * dma_buf operation. It alsog adjusts the starting pgoff and does bounds
 * checking on the size of the vma. Then it calls the exporters mmap function to
 * set up the mapping.
 *
 * Can return negative error values, returns 0 on success.
 */
int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
                 unsigned long pgoff)
{
        if (WARN_ON(!dmabuf || !vma))
                return -EINVAL;

        /* check for offset overflow */
        if (pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) < pgoff)
                return -EOVERFLOW;

        /* check for overflowing the buffer's size */
        if (pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) >
            dmabuf->size >> PAGE_SHIFT)
                return -EINVAL;

        /* readjust the vma */
        if (vma->vm_file)
                fput(vma->vm_file);

        vma->vm_file = dmabuf->file;
        get_file(vma->vm_file);

        vma->vm_pgoff = pgoff;

        return dmabuf->ops->mmap(dmabuf, vma);
}
EXPORT_SYMBOL_GPL(dma_buf_mmap);

/**
 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
 * address space. Same restrictions as for vmap and friends apply.
 * @dmabuf:     [in]    buffer to vmap
 *
 * This call may fail due to lack of virtual mapping address space.
 * These calls are optional in drivers. The intended use for them
 * is for mapping objects linear in kernel space for high use objects.
 * Please attempt to use kmap/kunmap before thinking about these interfaces.
 */
void *dma_buf_vmap(struct dma_buf *dmabuf)
{
        if (WARN_ON(!dmabuf))
                return NULL;

        if (dmabuf->ops->vmap)
                return dmabuf->ops->vmap(dmabuf);
        return NULL;
}
EXPORT_SYMBOL_GPL(dma_buf_vmap);

/**
 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
 * @dmabuf:     [in]    buffer to vunmap
 * @vaddr:      [in]    vmap to vunmap
 */
void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
{
        if (WARN_ON(!dmabuf))
                return;

        if (dmabuf->ops->vunmap)
                dmabuf->ops->vunmap(dmabuf, vaddr);
}
EXPORT_SYMBOL_GPL(dma_buf_vunmap);