/*
* videobuf2-dma-contig.c - DMA contig memory allocator for videobuf2
*
* Copyright (C) 2010 Samsung Electronics
*
* Author: Pawel Osciak <[email protected]>
*
* 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 <linux/highmem.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;
struct vb2_buffer *vb;
bool non_coherent_mem;
};
/*********************************************/
/* 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_sgtable_dma_sg(sgt, s, i) {
if (sg_dma_address(s) != expected)
break;
expected += sg_dma_len(s);
size += sg_dma_len(s);
}
return size;
}
/*********************************************/
/* callbacks for all buffers */
/*********************************************/
static void *vb2_dc_cookie(struct vb2_buffer *vb, void *buf_priv)
{
struct vb2_dc_buf *buf = buf_priv;
return &buf->dma_addr;
}
/*
* This function may fail if:
*
* - dma_buf_vmap() fails
* E.g. due to lack of virtual mapping address space, or due to
* dmabuf->ops misconfiguration.
*
* - dma_vmap_noncontiguous() fails
* For instance, when requested buffer size is larger than totalram_pages().
* Relevant for buffers that use non-coherent memory.
*
* - Queue DMA attrs have DMA_ATTR_NO_KERNEL_MAPPING set
* Relevant for buffers that use coherent memory.
*/
static void *vb2_dc_vaddr(struct vb2_buffer *vb, void *buf_priv)
{
struct vb2_dc_buf *buf = buf_priv;
if (buf->vaddr)
return buf->vaddr;
if (buf->db_attach) {
struct iosys_map map;
if (!dma_buf_vmap_unlocked(buf->db_attach->dmabuf, &map))
buf->vaddr = map.vaddr;
return buf->vaddr;
}
if (buf->non_coherent_mem)
buf->vaddr = dma_vmap_noncontiguous(buf->dev, buf->size,
buf->dma_sgt);
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;
/* This takes care of DMABUF and user-enforced cache sync hint */
if (buf->vb->skip_cache_sync_on_prepare)
return;
if (!buf->non_coherent_mem)
return;
/* Non-coherent MMAP only */
if (buf->vaddr)
flush_kernel_vmap_range(buf->vaddr, buf->size);
/* For both USERPTR and non-coherent MMAP */
dma_sync_sgtable_for_device(buf->dev, sgt, 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;
/* This takes care of DMABUF and user-enforced cache sync hint */
if (buf->vb->skip_cache_sync_on_finish)
return;
if (!buf->non_coherent_mem)
return;
/* Non-coherent MMAP only */
if (buf->vaddr)
invalidate_kernel_vmap_range(buf->vaddr, buf->size);
/* For both USERPTR and non-coherent MMAP */
dma_sync_sgtable_for_cpu(buf->dev, sgt, 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->non_coherent_mem) {
if (buf->vaddr)
dma_vunmap_noncontiguous(buf->dev, buf->vaddr);
dma_free_noncontiguous(buf->dev, buf->size,
buf->dma_sgt, buf->dma_dir);
} else {
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 int vb2_dc_alloc_coherent(struct vb2_dc_buf *buf)
{
struct vb2_queue *q = buf->vb->vb2_queue;
buf->cookie = dma_alloc_attrs(buf->dev,
buf->size,
&buf->dma_addr,
GFP_KERNEL | q->gfp_flags,
buf->attrs);
if (!buf->cookie)
return -ENOMEM;
if (q->dma_attrs & DMA_ATTR_NO_KERNEL_MAPPING)
return 0;
buf->vaddr = buf->cookie;
return 0;
}
static int vb2_dc_alloc_non_coherent(struct vb2_dc_buf *buf)
{
struct vb2_queue *q = buf->vb->vb2_queue;
buf->dma_sgt = dma_alloc_noncontiguous(buf->dev,
buf->size,
buf->dma_dir,
GFP_KERNEL | q->gfp_flags,
buf->attrs);
if (!buf->dma_sgt)
return -ENOMEM;
buf->dma_addr = sg_dma_address(buf->dma_sgt->sgl);
/*
* For non-coherent buffers the kernel mapping is created on demand
* in vb2_dc_vaddr().
*/
return 0;
}
static void *vb2_dc_alloc(struct vb2_buffer *vb,
struct device *dev,
unsigned long size)
{
struct vb2_dc_buf *buf;
int ret;
if (WARN_ON(!dev))
return ERR_PTR(-EINVAL);
buf = kzalloc(sizeof *buf, GFP_KERNEL);
if (!buf)
return ERR_PTR(-ENOMEM);
buf->attrs = vb->vb2_queue->dma_attrs;
buf->dma_dir = vb->vb2_queue->dma_dir;
buf->vb = vb;
buf->non_coherent_mem = vb->vb2_queue->non_coherent_mem;
buf->size = size;
/* Prevent the device from being released while the buffer is used */
buf->dev = get_device(dev);
if (buf->non_coherent_mem)
ret = vb2_dc_alloc_non_coherent(buf);
else
ret = vb2_dc_alloc_coherent(buf);
if (ret) {
dev_err(dev, "dma alloc of size %lu failed\n", size);
kfree(buf);
return ERR_PTR(-ENOMEM);
}
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;
}
if (buf->non_coherent_mem)
ret = dma_mmap_noncontiguous(buf->dev, vma, buf->size,
buf->dma_sgt);
else
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;
}
vm_flags_set(vma, 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 %lu\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 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)
/*
* Cache sync can be skipped here, as the vb2_dc memory is
* allocated from device coherent memory, which means the
* memory locations do not require any explicit cache
* maintenance prior or after being used by the device.
*/
dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir,
DMA_ATTR_SKIP_CPU_SYNC);
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;
struct sg_table *sgt;
sgt = &attach->sgt;
/* return previously mapped sg table */
if (attach->dma_dir == dma_dir)
return sgt;
/* release any previous cache */
if (attach->dma_dir != DMA_NONE) {
dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir,
DMA_ATTR_SKIP_CPU_SYNC);
attach->dma_dir = DMA_NONE;
}
/*
* mapping to the client with new direction, no cache sync
* required see comment in vb2_dc_dmabuf_ops_detach()
*/
if (dma_map_sgtable(db_attach->dev, sgt, dma_dir,
DMA_ATTR_SKIP_CPU_SYNC)) {
pr_err("failed to map scatterlist\n");
return ERR_PTR(-EIO);
}
attach->dma_dir = dma_dir;
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 int
vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
enum dma_data_direction direction)
{
return 0;
}
static int
vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
enum dma_data_direction direction)
{
return 0;
}
static int vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf, struct iosys_map *map)
{
struct vb2_dc_buf *buf;
void *vaddr;
buf = dbuf->priv;
vaddr = vb2_dc_vaddr(buf->vb, buf);
if (!vaddr)
return -EINVAL;
iosys_map_set_vaddr(map, vaddr);
return 0;
}
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,
.begin_cpu_access = vb2_dc_dmabuf_ops_begin_cpu_access,
.end_cpu_access = vb2_dc_dmabuf_ops_end_cpu_access,
.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;
if (buf->non_coherent_mem)
return buf->dma_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(struct vb2_buffer *vb,
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_sgtable(buf->dev, sgt, buf->dma_dir,
DMA_ATTR_SKIP_CPU_SYNC);
if (buf->dma_dir == DMA_FROM_DEVICE ||
buf->dma_dir == DMA_BIDIRECTIONAL) {
pages = frame_vector_pages(buf->vec);
/* sgt should exist only if vector contains pages... */
if (!WARN_ON_ONCE(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);
} else {
dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
buf->dma_dir, 0);
}
vb2_destroy_framevec(buf->vec);
kfree(buf);
}
static void *vb2_dc_get_userptr(struct vb2_buffer *vb, struct device *dev,
unsigned long vaddr, unsigned long size)
{
struct vb2_dc_buf *buf;
struct frame_vector *vec;
unsigned int 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 = vb->vb2_queue->dma_dir;
buf->vb = vb;
offset = lower_32_bits(offset_in_page(vaddr));
vec = vb2_create_framevec(vaddr, size, buf->dma_dir == DMA_FROM_DEVICE ||
buf->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 = dma_map_resource(buf->dev,
__pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
if (dma_mapping_error(buf->dev, buf->dma_addr)) {
ret = -ENOMEM;
goto fail_pfnvec;
}
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.
*/
if (dma_map_sgtable(buf->dev, sgt, buf->dma_dir,
DMA_ATTR_SKIP_CPU_SYNC)) {
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;
buf->non_coherent_mem = 1;
out:
buf->size = size;
return buf;
fail_map_sg:
dma_unmap_sgtable(buf->dev, sgt, 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_unlocked(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\n",
contig_size, buf->size);
dma_buf_unmap_attachment_unlocked(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;
struct iosys_map map = IOSYS_MAP_INIT_VADDR(buf->vaddr);
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_unlocked(buf->db_attach->dmabuf, &map);
buf->vaddr = NULL;
}
dma_buf_unmap_attachment_unlocked(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 vb2_buffer *vb, struct device *dev,
struct dma_buf *dbuf, unsigned long size)
{
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;
buf->vb = vb;
/* 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 = vb->vb2_queue->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_err(dev, "Failed to set max_seg_size: dma_parms is NULL\n");
return -ENODEV;
}
if (dma_get_max_seg_size(dev) < size)
dma_set_max_seg_size(dev, size);
return 0;
}
EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
MODULE_AUTHOR("Pawel Osciak <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(DMA_BUF);
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