/*
 * videobuf2-dma-contig.c - DMA contig memory allocator for videobuf2
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Pawel Osciak <pawel@osciak.com>
 *
 * 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.
 */

#include <linux/dma-buf.h>
#include <linux/module.h>
#include <linux/refcount.h>
#include <linux/scatterlist.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/dma-mapping.h>

#include <media/videobuf2-v4l2.h>
#include <media/videobuf2-dma-contig.h>
#include <media/videobuf2-memops.h>

struct vb2_dc_buf {
        struct device                   *dev;
        void                            *vaddr;
        unsigned long                   size;
        void                            *cookie;
        dma_addr_t                      dma_addr;
        unsigned long                   attrs;
        enum dma_data_direction         dma_dir;
        struct sg_table                 *dma_sgt;
        struct frame_vector             *vec;

        /* MMAP related */
        struct vb2_vmarea_handler       handler;
        refcount_t                      refcount;
        struct sg_table                 *sgt_base;

        /* DMABUF related */
        struct dma_buf_attachment       *db_attach;
};

/*********************************************/
/*        scatterlist table functions        */
/*********************************************/

static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt)
{
        struct scatterlist *s;
        dma_addr_t expected = sg_dma_address(sgt->sgl);
        unsigned int i;
        unsigned long size = 0;

        for_each_sg(sgt->sgl, s, sgt->nents, i) {
                if (sg_dma_address(s) != expected)
                        break;
                expected = sg_dma_address(s) + sg_dma_len(s);
                size += sg_dma_len(s);
        }
        return size;
}

/*********************************************/
/*         callbacks for all buffers         */
/*********************************************/

static void *vb2_dc_cookie(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        return &buf->dma_addr;
}

static void *vb2_dc_vaddr(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        if (!buf->vaddr && buf->db_attach)
                buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);

        return buf->vaddr;
}

static unsigned int vb2_dc_num_users(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        return refcount_read(&buf->refcount);
}

static void vb2_dc_prepare(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

        /* DMABUF exporter will flush the cache for us */
        if (!sgt || buf->db_attach)
                return;

        dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
                               buf->dma_dir);
}

static void vb2_dc_finish(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

        /* DMABUF exporter will flush the cache for us */
        if (!sgt || buf->db_attach)
                return;

        dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
}

/*********************************************/
/*        callbacks for MMAP buffers         */
/*********************************************/

static void vb2_dc_put(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        if (!refcount_dec_and_test(&buf->refcount))
                return;

        if (buf->sgt_base) {
                sg_free_table(buf->sgt_base);
                kfree(buf->sgt_base);
        }
        dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr,
                       buf->attrs);
        put_device(buf->dev);
        kfree(buf);
}

static void *vb2_dc_alloc(struct device *dev, unsigned long attrs,
                          unsigned long size, enum dma_data_direction dma_dir,
                          gfp_t gfp_flags)
{
        struct vb2_dc_buf *buf;

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

        buf = kzalloc(sizeof *buf, GFP_KERNEL);
        if (!buf)
                return ERR_PTR(-ENOMEM);

        if (attrs)
                buf->attrs = attrs;
        buf->cookie = dma_alloc_attrs(dev, size, &buf->dma_addr,
                                        GFP_KERNEL | gfp_flags, buf->attrs);
        if (!buf->cookie) {
                dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
                kfree(buf);
                return ERR_PTR(-ENOMEM);
        }

        if ((buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
                buf->vaddr = buf->cookie;

        /* Prevent the device from being released while the buffer is used */
        buf->dev = get_device(dev);
        buf->size = size;
        buf->dma_dir = dma_dir;

        buf->handler.refcount = &buf->refcount;
        buf->handler.put = vb2_dc_put;
        buf->handler.arg = buf;

        refcount_set(&buf->refcount, 1);

        return buf;
}

static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
{
        struct vb2_dc_buf *buf = buf_priv;
        int ret;

        if (!buf) {
                printk(KERN_ERR "No buffer to map\n");
                return -EINVAL;
        }

        /*
         * dma_mmap_* uses vm_pgoff as in-buffer offset, but we want to
         * map whole buffer
         */
        vma->vm_pgoff = 0;

        ret = dma_mmap_attrs(buf->dev, vma, buf->cookie,
                buf->dma_addr, buf->size, buf->attrs);

        if (ret) {
                pr_err("Remapping memory failed, error: %d\n", ret);
                return ret;
        }

        vma->vm_flags           |= VM_DONTEXPAND | VM_DONTDUMP;
        vma->vm_private_data    = &buf->handler;
        vma->vm_ops             = &vb2_common_vm_ops;

        vma->vm_ops->open(vma);

        pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %ld\n",
                __func__, (unsigned long)buf->dma_addr, vma->vm_start,
                buf->size);

        return 0;
}

/*********************************************/
/*         DMABUF ops for exporters          */
/*********************************************/

struct vb2_dc_attachment {
        struct sg_table sgt;
        enum dma_data_direction dma_dir;
};

static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
        struct dma_buf_attachment *dbuf_attach)
{
        struct vb2_dc_attachment *attach;
        unsigned int i;
        struct scatterlist *rd, *wr;
        struct sg_table *sgt;
        struct vb2_dc_buf *buf = dbuf->priv;
        int ret;

        attach = kzalloc(sizeof(*attach), GFP_KERNEL);
        if (!attach)
                return -ENOMEM;

        sgt = &attach->sgt;
        /* Copy the buf->base_sgt scatter list to the attachment, as we can't
         * map the same scatter list to multiple attachments at the same time.
         */
        ret = sg_alloc_table(sgt, buf->sgt_base->orig_nents, GFP_KERNEL);
        if (ret) {
                kfree(attach);
                return -ENOMEM;
        }

        rd = buf->sgt_base->sgl;
        wr = sgt->sgl;
        for (i = 0; i < sgt->orig_nents; ++i) {
                sg_set_page(wr, sg_page(rd), rd->length, rd->offset);
                rd = sg_next(rd);
                wr = sg_next(wr);
        }

        attach->dma_dir = DMA_NONE;
        dbuf_attach->priv = attach;

        return 0;
}

static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
        struct dma_buf_attachment *db_attach)
{
        struct vb2_dc_attachment *attach = db_attach->priv;
        struct sg_table *sgt;

        if (!attach)
                return;

        sgt = &attach->sgt;

        /* release the scatterlist cache */
        if (attach->dma_dir != DMA_NONE)
                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
                        attach->dma_dir);
        sg_free_table(sgt);
        kfree(attach);
        db_attach->priv = NULL;
}

static struct sg_table *vb2_dc_dmabuf_ops_map(
        struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
{
        struct vb2_dc_attachment *attach = db_attach->priv;
        /* stealing dmabuf mutex to serialize map/unmap operations */
        struct mutex *lock = &db_attach->dmabuf->lock;
        struct sg_table *sgt;

        mutex_lock(lock);

        sgt = &attach->sgt;
        /* return previously mapped sg table */
        if (attach->dma_dir == dma_dir) {
                mutex_unlock(lock);
                return sgt;
        }

        /* release any previous cache */
        if (attach->dma_dir != DMA_NONE) {
                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
                        attach->dma_dir);
                attach->dma_dir = DMA_NONE;
        }

        /* mapping to the client with new direction */
        sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
                                dma_dir);
        if (!sgt->nents) {
                pr_err("failed to map scatterlist\n");
                mutex_unlock(lock);
                return ERR_PTR(-EIO);
        }

        attach->dma_dir = dma_dir;

        mutex_unlock(lock);

        return sgt;
}

static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
        struct sg_table *sgt, enum dma_data_direction dma_dir)
{
        /* nothing to be done here */
}

static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
{
        /* drop reference obtained in vb2_dc_get_dmabuf */
        vb2_dc_put(dbuf->priv);
}

static void *vb2_dc_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
{
        struct vb2_dc_buf *buf = dbuf->priv;

        return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
}

static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
{
        struct vb2_dc_buf *buf = dbuf->priv;

        return buf->vaddr;
}

static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
        struct vm_area_struct *vma)
{
        return vb2_dc_mmap(dbuf->priv, vma);
}

static const struct dma_buf_ops vb2_dc_dmabuf_ops = {
        .attach = vb2_dc_dmabuf_ops_attach,
        .detach = vb2_dc_dmabuf_ops_detach,
        .map_dma_buf = vb2_dc_dmabuf_ops_map,
        .unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
        .map = vb2_dc_dmabuf_ops_kmap,
        .map_atomic = vb2_dc_dmabuf_ops_kmap,
        .vmap = vb2_dc_dmabuf_ops_vmap,
        .mmap = vb2_dc_dmabuf_ops_mmap,
        .release = vb2_dc_dmabuf_ops_release,
};

static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
{
        int ret;
        struct sg_table *sgt;

        sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
        if (!sgt) {
                dev_err(buf->dev, "failed to alloc sg table\n");
                return NULL;
        }

        ret = dma_get_sgtable_attrs(buf->dev, sgt, buf->cookie, buf->dma_addr,
                buf->size, buf->attrs);
        if (ret < 0) {
                dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
                kfree(sgt);
                return NULL;
        }

        return sgt;
}

static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct dma_buf *dbuf;
        DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

        exp_info.ops = &vb2_dc_dmabuf_ops;
        exp_info.size = buf->size;
        exp_info.flags = flags;
        exp_info.priv = buf;

        if (!buf->sgt_base)
                buf->sgt_base = vb2_dc_get_base_sgt(buf);

        if (WARN_ON(!buf->sgt_base))
                return NULL;

        dbuf = dma_buf_export(&exp_info);
        if (IS_ERR(dbuf))
                return NULL;

        /* dmabuf keeps reference to vb2 buffer */
        refcount_inc(&buf->refcount);

        return dbuf;
}

/*********************************************/
/*       callbacks for USERPTR buffers       */
/*********************************************/

static void vb2_dc_put_userptr(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;
        int i;
        struct page **pages;

        if (sgt) {
                /*
                 * No need to sync to CPU, it's already synced to the CPU
                 * since the finish() memop will have been called before this.
                 */
                dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
                                   buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
                pages = frame_vector_pages(buf->vec);
                /* sgt should exist only if vector contains pages... */
                BUG_ON(IS_ERR(pages));
                for (i = 0; i < frame_vector_count(buf->vec); i++)
                        set_page_dirty_lock(pages[i]);
                sg_free_table(sgt);
                kfree(sgt);
        }
        vb2_destroy_framevec(buf->vec);
        kfree(buf);
}

/*
 * For some kind of reserved memory there might be no struct page available,
 * so all that can be done to support such 'pages' is to try to convert
 * pfn to dma address or at the last resort just assume that
 * dma address == physical address (like it has been assumed in earlier version
 * of videobuf2-dma-contig
 */

#ifdef __arch_pfn_to_dma
static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
{
        return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
}
#elif defined(__pfn_to_bus)
static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
{
        return (dma_addr_t)__pfn_to_bus(pfn);
}
#elif defined(__pfn_to_phys)
static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
{
        return (dma_addr_t)__pfn_to_phys(pfn);
}
#else
static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
{
        /* really, we cannot do anything better at this point */
        return (dma_addr_t)(pfn) << PAGE_SHIFT;
}
#endif

static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
        unsigned long size, enum dma_data_direction dma_dir)
{
        struct vb2_dc_buf *buf;
        struct frame_vector *vec;
        unsigned long offset;
        int n_pages, i;
        int ret = 0;
        struct sg_table *sgt;
        unsigned long contig_size;
        unsigned long dma_align = dma_get_cache_alignment();

        /* Only cache aligned DMA transfers are reliable */
        if (!IS_ALIGNED(vaddr | size, dma_align)) {
                pr_debug("user data must be aligned to %lu bytes\n", dma_align);
                return ERR_PTR(-EINVAL);
        }

        if (!size) {
                pr_debug("size is zero\n");
                return ERR_PTR(-EINVAL);
        }

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

        buf = kzalloc(sizeof *buf, GFP_KERNEL);
        if (!buf)
                return ERR_PTR(-ENOMEM);

        buf->dev = dev;
        buf->dma_dir = dma_dir;

        offset = vaddr & ~PAGE_MASK;
        vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE ||
                                               dma_dir == DMA_BIDIRECTIONAL);
        if (IS_ERR(vec)) {
                ret = PTR_ERR(vec);
                goto fail_buf;
        }
        buf->vec = vec;
        n_pages = frame_vector_count(vec);
        ret = frame_vector_to_pages(vec);
        if (ret < 0) {
                unsigned long *nums = frame_vector_pfns(vec);

                /*
                 * Failed to convert to pages... Check the memory is physically
                 * contiguous and use direct mapping
                 */
                for (i = 1; i < n_pages; i++)
                        if (nums[i-1] + 1 != nums[i])
                                goto fail_pfnvec;
                buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
                goto out;
        }

        sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
        if (!sgt) {
                pr_err("failed to allocate sg table\n");
                ret = -ENOMEM;
                goto fail_pfnvec;
        }

        ret = sg_alloc_table_from_pages(sgt, frame_vector_pages(vec), n_pages,
                offset, size, GFP_KERNEL);
        if (ret) {
                pr_err("failed to initialize sg table\n");
                goto fail_sgt;
        }

        /*
         * No need to sync to the device, this will happen later when the
         * prepare() memop is called.
         */
        sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
                                      buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
        if (sgt->nents <= 0) {
                pr_err("failed to map scatterlist\n");
                ret = -EIO;
                goto fail_sgt_init;
        }

        contig_size = vb2_dc_get_contiguous_size(sgt);
        if (contig_size < size) {
                pr_err("contiguous mapping is too small %lu/%lu\n",
                        contig_size, size);
                ret = -EFAULT;
                goto fail_map_sg;
        }

        buf->dma_addr = sg_dma_address(sgt->sgl);
        buf->dma_sgt = sgt;
out:
        buf->size = size;

        return buf;

fail_map_sg:
        dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
                           buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);

fail_sgt_init:
        sg_free_table(sgt);

fail_sgt:
        kfree(sgt);

fail_pfnvec:
        vb2_destroy_framevec(vec);

fail_buf:
        kfree(buf);

        return ERR_PTR(ret);
}

/*********************************************/
/*       callbacks for DMABUF buffers        */
/*********************************************/

static int vb2_dc_map_dmabuf(void *mem_priv)
{
        struct vb2_dc_buf *buf = mem_priv;
        struct sg_table *sgt;
        unsigned long contig_size;

        if (WARN_ON(!buf->db_attach)) {
                pr_err("trying to pin a non attached buffer\n");
                return -EINVAL;
        }

        if (WARN_ON(buf->dma_sgt)) {
                pr_err("dmabuf buffer is already pinned\n");
                return 0;
        }

        /* get the associated scatterlist for this buffer */
        sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
        if (IS_ERR(sgt)) {
                pr_err("Error getting dmabuf scatterlist\n");
                return -EINVAL;
        }

        /* checking if dmabuf is big enough to store contiguous chunk */
        contig_size = vb2_dc_get_contiguous_size(sgt);
        if (contig_size < buf->size) {
                pr_err("contiguous chunk is too small %lu/%lu b\n",
                        contig_size, buf->size);
                dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
                return -EFAULT;
        }

        buf->dma_addr = sg_dma_address(sgt->sgl);
        buf->dma_sgt = sgt;
        buf->vaddr = NULL;

        return 0;
}

static void vb2_dc_unmap_dmabuf(void *mem_priv)
{
        struct vb2_dc_buf *buf = mem_priv;
        struct sg_table *sgt = buf->dma_sgt;

        if (WARN_ON(!buf->db_attach)) {
                pr_err("trying to unpin a not attached buffer\n");
                return;
        }

        if (WARN_ON(!sgt)) {
                pr_err("dmabuf buffer is already unpinned\n");
                return;
        }

        if (buf->vaddr) {
                dma_buf_vunmap(buf->db_attach->dmabuf, buf->vaddr);
                buf->vaddr = NULL;
        }
        dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);

        buf->dma_addr = 0;
        buf->dma_sgt = NULL;
}

static void vb2_dc_detach_dmabuf(void *mem_priv)
{
        struct vb2_dc_buf *buf = mem_priv;

        /* if vb2 works correctly you should never detach mapped buffer */
        if (WARN_ON(buf->dma_addr))
                vb2_dc_unmap_dmabuf(buf);

        /* detach this attachment */
        dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
        kfree(buf);
}

static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
        unsigned long size, enum dma_data_direction dma_dir)
{
        struct vb2_dc_buf *buf;
        struct dma_buf_attachment *dba;

        if (dbuf->size < size)
                return ERR_PTR(-EFAULT);

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

        buf = kzalloc(sizeof(*buf), GFP_KERNEL);
        if (!buf)
                return ERR_PTR(-ENOMEM);

        buf->dev = dev;
        /* create attachment for the dmabuf with the user device */
        dba = dma_buf_attach(dbuf, buf->dev);
        if (IS_ERR(dba)) {
                pr_err("failed to attach dmabuf\n");
                kfree(buf);
                return dba;
        }

        buf->dma_dir = dma_dir;
        buf->size = size;
        buf->db_attach = dba;

        return buf;
}

/*********************************************/
/*       DMA CONTIG exported functions       */
/*********************************************/

const struct vb2_mem_ops vb2_dma_contig_memops = {
        .alloc          = vb2_dc_alloc,
        .put            = vb2_dc_put,
        .get_dmabuf     = vb2_dc_get_dmabuf,
        .cookie         = vb2_dc_cookie,
        .vaddr          = vb2_dc_vaddr,
        .mmap           = vb2_dc_mmap,
        .get_userptr    = vb2_dc_get_userptr,
        .put_userptr    = vb2_dc_put_userptr,
        .prepare        = vb2_dc_prepare,
        .finish         = vb2_dc_finish,
        .map_dmabuf     = vb2_dc_map_dmabuf,
        .unmap_dmabuf   = vb2_dc_unmap_dmabuf,
        .attach_dmabuf  = vb2_dc_attach_dmabuf,
        .detach_dmabuf  = vb2_dc_detach_dmabuf,
        .num_users      = vb2_dc_num_users,
};
EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);

/**
 * vb2_dma_contig_set_max_seg_size() - configure DMA max segment size
 * @dev:        device for configuring DMA parameters
 * @size:       size of DMA max segment size to set
 *
 * To allow mapping the scatter-list into a single chunk in the DMA
 * address space, the device is required to have the DMA max segment
 * size parameter set to a value larger than the buffer size. Otherwise,
 * the DMA-mapping subsystem will split the mapping into max segment
 * size chunks. This function sets the DMA max segment size
 * parameter to let DMA-mapping map a buffer as a single chunk in DMA
 * address space.
 * This code assumes that the DMA-mapping subsystem will merge all
 * scatterlist segments if this is really possible (for example when
 * an IOMMU is available and enabled).
 * Ideally, this parameter should be set by the generic bus code, but it
 * is left with the default 64KiB value due to historical litmiations in
 * other subsystems (like limited USB host drivers) and there no good
 * place to set it to the proper value.
 * This function should be called from the drivers, which are known to
 * operate on platforms with IOMMU and provide access to shared buffers
 * (either USERPTR or DMABUF). This should be done before initializing
 * videobuf2 queue.
 */
int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
{
        if (!dev->dma_parms) {
                dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
                if (!dev->dma_parms)
                        return -ENOMEM;
        }
        if (dma_get_max_seg_size(dev) < size)
                return dma_set_max_seg_size(dev, size);

        return 0;
}
EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);

/*
 * vb2_dma_contig_clear_max_seg_size() - release resources for DMA parameters
 * @dev:        device for configuring DMA parameters
 *
 * This function releases resources allocated to configure DMA parameters
 * (see vb2_dma_contig_set_max_seg_size() function). It should be called from
 * device drivers on driver remove.
 */
void vb2_dma_contig_clear_max_seg_size(struct device *dev)
{
        kfree(dev->dma_parms);
        dev->dma_parms = NULL;
}
EXPORT_SYMBOL_GPL(vb2_dma_contig_clear_max_seg_size);

MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
MODULE_LICENSE("GPL");