[Linaro-mm-sig] [RFCv2 PATCH 2/9 - 4/4] v4l: vb2-dma-contig: update and code refactoring
Tomasz Stanislawski
t.stanislaws at samsung.com
Thu Mar 22 06:36:33 PDT 2012
Hi Laurent,
Thank you very much for your comments and question.
They were very useful.
Please refer to the comments below.
On 03/22/2012 11:50 AM, Laurent Pinchart wrote:
> Hi Tomasz,
>
> Thanks for the patch.
>
> On Thursday 22 March 2012 11:02:23 Laurent Pinchart wrote:
>> From: Tomasz Stanislawski <t.stanislaws at samsung.com>
>>
>> This patch combines updates and fixes to dma-contig allocator.
>> Moreover the allocator code was refactored.
>> The most important changes are:
>> - functions were reordered
>> - move compression of scatterlist to separete function
>> - add support for multichunk but contiguous scatterlists
>> - simplified implementation of vb2-dma-contig context structure
>> - let mmap method to use dma_mmap_writecombine
>> - add support for scatterlist in userptr mode
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>> [mmap method]
>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p at samsung.com>
>> [scatterlist in userptr mode]
>> Signed-off-by: Kamil Debski <k.debski at samsung.com>
>> [bugfixing]
>> Signed-off-by: Tomasz Stanislawski <t.stanislaws at samsung.com>
>> [core refactoring, helper functions]
>> Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
>> ---
>> drivers/media/video/videobuf2-dma-contig.c | 400
>> +++++++++++++++++++++++++--- 1 files changed, 365 insertions(+), 35
>> deletions(-)
>>
>> diff --git a/drivers/media/video/videobuf2-dma-contig.c
>> b/drivers/media/video/videobuf2-dma-contig.c index c898e6f..9965465 100644
>> --- a/drivers/media/video/videobuf2-dma-contig.c
>> +++ b/drivers/media/video/videobuf2-dma-contig.c
>> @@ -10,9 +10,12 @@
>> * the Free Software Foundation.
>> */
>>
>> +#include <linux/dma-buf.h>
>> +#include <linux/dma-mapping.h>
>> #include <linux/module.h>
>> +#include <linux/scatterlist.h>
>> +#include <linux/sched.h>
>> #include <linux/slab.h>
>> -#include <linux/dma-mapping.h>
>>
>> #include <media/videobuf2-core.h>
>> #include <media/videobuf2-memops.h>
>> @@ -22,16 +25,115 @@ struct vb2_dc_buf {
>> void *vaddr;
>> unsigned long size;
>> dma_addr_t dma_addr;
>> + struct sg_table *dma_sgt;
>> + enum dma_data_direction dma_dir;
>>
>> /* MMAP related */
>> struct vb2_vmarea_handler handler;
>> atomic_t refcount;
>> + struct sg_table *sgt_base;
>>
>> /* USERPTR related */
>> struct vm_area_struct *vma;
>> };
>>
>> /*********************************************/
>> +/* scatterlist table functions */
>> +/*********************************************/
>> +
>> +static struct sg_table *vb2_dc_pages_to_sgt(struct page **pages,
>> + unsigned long n_pages, size_t offset, size_t offset2)
>> +{
>> + struct sg_table *sgt;
>> + int i, j; /* loop counters */
>> + int cur_page, chunks;
>> + int ret;
>> + struct scatterlist *s;
>> +
>> + sgt = kzalloc(sizeof *sgt, GFP_KERNEL);
>> + if (!sgt)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + /* compute number of chunks */
>> + chunks = 1;
>> + for (i = 1; i < n_pages; ++i)
>> + if (pages[i] != pages[i - 1] + 1)
>> + ++chunks;
>> +
>> + ret = sg_alloc_table(sgt, chunks, GFP_KERNEL);
>> + if (ret) {
>> + kfree(sgt);
>> + return ERR_PTR(-ENOMEM);
>> + }
>> +
>> + /* merging chunks and putting them into the scatterlist */
>> + cur_page = 0;
>> + for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
>> + size_t size = PAGE_SIZE;
>> +
>> + for (j = cur_page + 1; j < n_pages; ++j) {
>> + if (pages[j] != pages[j - 1] + 1)
>> + break;
>> + size += PAGE_SIZE;
>> + }
>> +
>> + /* cut offset if chunk starts at the first page */
>> + if (cur_page == 0)
>> + size -= offset;
>> + /* cut offset2 if chunk ends at the last page */
>> + if (j == n_pages)
>> + size -= offset2;
>> +
>> + sg_set_page(s, pages[cur_page], size, offset);
>> + offset = 0;
>> + cur_page = j;
>> + }
>> +
>> + return sgt;
>> +}
>> +
>> +static void vb2_dc_release_sgtable(struct sg_table *sgt)
>> +{
>> + sg_free_table(sgt);
>> + kfree(sgt);
>> +}
>> +
>> +static void vb2_dc_put_sgtable(struct sg_table *sgt, int dirty)
>> +{
>> + struct scatterlist *s;
>> + int i, j;
>> +
>> + for_each_sg(sgt->sgl, s, sgt->nents, i) {
>> + struct page *page = sg_page(s);
>> + int n_pages = PAGE_ALIGN(s->offset + s->length) >> PAGE_SHIFT;
>> +
>> + for (j = 0; j < n_pages; ++j, ++page) {
>> + if (dirty)
>> + set_page_dirty_lock(page);
>> + put_page(page);
>> + }
>> + }
>> +
>> + vb2_dc_release_sgtable(sgt);
>> +}
>> +
>> +static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt)
>> +{
>> + struct scatterlist *s;
>> + dma_addr_t expected = sg_dma_address(sgt->sgl);
>> + 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 */
>> /*********************************************/
>>
>> @@ -45,8 +147,6 @@ static void *vb2_dc_cookie(void *buf_priv)
>> static void *vb2_dc_vaddr(void *buf_priv)
>> {
>> struct vb2_dc_buf *buf = buf_priv;
>> - if (!buf)
>> - return 0;
>>
>> return buf->vaddr;
>> }
>> @@ -58,6 +158,28 @@ static unsigned int vb2_dc_num_users(void *buf_priv)
>> return atomic_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;
>> +
>> + if (!sgt)
>> + return;
>> +
>> + dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->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;
>> +
>> + if (!sgt)
>> + return;
>> +
>> + dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
>> +}
>> +
>> /*********************************************/
>> /* callbacks for MMAP buffers */
>> /*********************************************/
>> @@ -66,31 +188,70 @@ static void vb2_dc_put(void *buf_priv)
>> {
>> struct vb2_dc_buf *buf = buf_priv;
>>
>> - if (atomic_dec_and_test(&buf->refcount)) {
>> - dma_free_coherent(buf->dev, buf->size, buf->vaddr,
>> - buf->dma_addr);
>> - kfree(buf);
>> - }
>> + if (!atomic_dec_and_test(&buf->refcount))
>> + return;
>> +
>> + vb2_dc_release_sgtable(buf->sgt_base);
>> + dma_free_coherent(buf->dev, buf->size, buf->vaddr,
>> + buf->dma_addr);
>> + kfree(buf);
>> }
>>
>> static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size)
>> {
>> struct device *dev = alloc_ctx;
>> struct vb2_dc_buf *buf;
>> + int ret;
>> + int n_pages;http://165.213.219.115/cgi-bin/gitweb.cgi?p=mirror/linux-3.0-midas;a=shortlog;h=refs/heads/exynos-3.0-dev
>> + struct page **pages = NULL;
>>
>> buf = kzalloc(sizeof *buf, GFP_KERNEL);
>> if (!buf)
>> return ERR_PTR(-ENOMEM);
>>
>> - buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr, GFP_KERNEL);
>> + buf->dev = dev;
>> + buf->size = size;
>> + buf->vaddr = dma_alloc_coherent(buf->dev, buf->size, &buf->dma_addr,
>> + GFP_KERNEL);
>> +
>> + ret = -ENOMEM;
>> if (!buf->vaddr) {
>> - dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
>> - kfree(buf);
>> - return ERR_PTR(-ENOMEM);
>> + dev_err(dev, "dma_alloc_coherent of size %ld failed\n",
>> + size);
>> + goto fail_buf;
>> }
>>
>> - buf->dev = dev;
>> - buf->size = size;
>> + WARN_ON((unsigned long)buf->vaddr & ~PAGE_MASK);
>> + WARN_ON(buf->dma_addr & ~PAGE_MASK);
>> +
>> + n_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>> +
>> + pages = kmalloc(n_pages * sizeof pages[0], GFP_KERNEL);
>> + if (!pages) {
>> + printk(KERN_ERR "failed to alloc page table\n");
>> + goto fail_dma;
>> + }
>> +
>> + ret = dma_get_pages(dev, buf->vaddr, buf->dma_addr, pages, n_pages);
>
> As the only purpose of this is to retrieve a list of pages that will be used
> to create a single-entry sgt, wouldn't it be possible to shortcut the code and
> get the physical address of the buffer directly ?
>
The physical address should not be used since they are meaningless in a context of
different devices. It seams that only the list of pages is more-or-less portable
between different drivers.
The physical address is already present in buf->dma_addr, but it is only valid
if the device has no MMU. Notice that vb2-dma-contig possess no knowledge if
MMU is present for a given device.
The sg list is not going to be single-entry if the device is provided with its own MMU.
>> + if (ret < 0) {
>> + printk(KERN_ERR "failed to get buffer pages from DMA API\n");
>> + goto fail_pages;
>> + }
>> + if (ret != n_pages) {
>> + ret = -EFAULT;
>> + printk(KERN_ERR "failed to get all pages from DMA API\n");
>> + goto fail_pages;
>> + }
>> +
>> + buf->sgt_base = vb2_dc_pages_to_sgt(pages, n_pages, 0, 0);
>> + if (IS_ERR(buf->sgt_base)) {
>> + ret = PTR_ERR(buf->sgt_base);
>> + printk(KERN_ERR "failed to prepare sg table\n");
>> + goto fail_pages;
>> + }
>
> buf->sgt_base isn't used in this patch. I would move the buf->sgt_base
> creation code to the patch that uses it then, or to its own patch just before
> the patch that uses it.
Good point. The sgt_base is used by exporter only. Thanks for noticing it.
>
>> +
>> + /* pages are no longer needed */
>> + kfree(pages);
>>
>> buf->handler.refcount = &buf->refcount;
>> buf->handler.put = vb2_dc_put;
>> @@ -99,59 +260,226 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned
>> long size) atomic_inc(&buf->refcount);
>>
>> return buf;
>> +
>> +fail_pages:
>> + kfree(pages);
>> +
>> +fail_dma:
>> + dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr);
>> +
>> +fail_buf:
>> + kfree(buf);
>> +
>> + return ERR_PTR(ret);
>> }
>>
>> static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
>> {
>> struct vb2_dc_buf *buf = buf_priv;
>> + int ret;
>> +
>> + /*
>> + * dma_mmap_* uses vm_pgoff as in-buffer offset, but we want to
>> + * map whole buffer
>> + */
>> + vma->vm_pgoff = 0;
>> +
>> + ret = dma_mmap_writecombine(buf->dev, vma, buf->vaddr,
>> + buf->dma_addr, buf->size);
>>
>> - if (!buf) {
>> - printk(KERN_ERR "No buffer to map\n");
>> - return -EINVAL;
>> + if (ret) {
>> + printk(KERN_ERR "Remapping memory failed, error: %d\n", ret);
>> + return ret;
>> }
>>
>> - return vb2_mmap_pfn_range(vma, buf->dma_addr, buf->size,
>> - &vb2_common_vm_ops, &buf->handler);
>> + vma->vm_flags |= VM_DONTEXPAND | VM_RESERVED;
>> + vma->vm_private_data = &buf->handler;
>> + vma->vm_ops = &vb2_common_vm_ops;
>> +
>> + vma->vm_ops->open(vma);
>> +
>> + printk(KERN_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;
>> }
>>
>> /*********************************************/
>> /* callbacks for USERPTR buffers */
>> /*********************************************/
>>
>> +static inline int vma_is_io(struct vm_area_struct *vma)
>> +{
>> + return !!(vma->vm_flags & (VM_IO | VM_PFNMAP));
>
> Isn't VM_PFNMAP enough ? Wouldn't it be possible (at least in theory) to get a
> discontinuous physical range with VM_IO ?
>
Frankly, I found that that in get_user_pages flags are checked against
(VM_IO | VM_PFNMAP). Probably for noMMU (not no IOMMU) case it is possible
to get vma with VM_IO on and VM_PFNMAP off, isn't it?
The problem is that this framework should work in both cases so this
check was added just in case :).
>> +}
>> +
>> +static int vb2_dc_get_pages(unsigned long start, struct page **pages,
>> + int n_pages, struct vm_area_struct **copy_vma, int write)
>> +{
>> + struct vm_area_struct *vma;
>> + int n = 0; /* number of get pages */
>> + int ret = -EFAULT;
>> +
>> + /* entering critical section for mm access */
>> + down_read(¤t->mm->mmap_sem);
>
> This will generate AB-BA deadlock warnings if lockdep is enabled. This
> function is called with the queue lock held, and the mmap() handler which
> takes the queue lock is called with current->mm->mmap_sem held.
>
> This is a known issue with videobuf2, not specific to this patch. The warning
> is usually a false positive (which we still need to fix, as it worries users),
> but can become a real issue if an MMAP queue and a USERPTR queue are created
> by a driver with the same queue lock.
>
Good point. Do you know any good solution to this problem?
>> + vma = find_vma(current->mm, start);
>> + if (!vma) {
>> + printk(KERN_ERR "no vma for address %lu\n", start);
>> + goto cleanup;
>> + }
>> +
>> + if (vma_is_io(vma)) {
>> + unsigned long pfn;
>> +
>> + if (vma->vm_end - start < n_pages * PAGE_SIZE) {
>> + printk(KERN_ERR "vma is too small\n");
>> + goto cleanup;
>> + }
>> +
>> + for (n = 0; n < n_pages; ++n, start += PAGE_SIZE) {
>> + ret = follow_pfn(vma, start, &pfn);
>> + if (ret) {
>> + printk(KERN_ERR "no page for address %lu\n",
>> + start);
>> + goto cleanup;
>> + }
>> + pages[n] = pfn_to_page(pfn);
>> + get_page(pages[n]);
>
> This worries me. When the VM_PFNMAP flag is set, the memory pages are not
> backed by a struct page. Creating a struct page pointer out of it can be an
> acceptable hack (for instance to store a page in an scatterlist with
> sg_set_page() and then retrieve its physical address with sg_phys()), but you
> should not expect the struct page to be valid for anything else. Calling
> get_page() on it will likely crash.
>
You are completetly right. This is the corner case where list of pages is
not a portable way of describing the memory.
Maybe pfn_valid should be used to check validity of the page (pfn)
before getting it?
>> + }
>> + } else {
>> + n = get_user_pages(current, current->mm, start & PAGE_MASK,
>> + n_pages, write, 1, pages, NULL);
>> + if (n != n_pages) {
>> + printk(KERN_ERR "got only %d of %d user pages\n",
>> + n, n_pages);
>> + goto cleanup;
>> + }
>> + }
>> +
>> + *copy_vma = vb2_get_vma(vma);
>> + if (!*copy_vma) {
>> + printk(KERN_ERR "failed to copy vma\n");
>> + ret = -ENOMEM;
>> + goto cleanup;
>> + }
>
> Do we really need to make a copy of the VMA ? The only reason why we store a
> pointer to it is to check the flags in vb2_dc_put_userptr(). We could store
> the flags instead and avoid vb2_get_dma()/vb2_put_dma() calls altogether.
>
I remember that there was a very good reason of copying this vma structure.
You caught me on 'cargo-cult' programming.
I will do some reverse engineering and try to answer it soon.
>> +
>> + /* leaving critical section for mm access */
>> + up_read(¤t->mm->mmap_sem);
>> +
>> + return 0;
>> +
>> +cleanup:
>> + up_read(¤t->mm->mmap_sem);
>> +
>> + /* putting user pages if used, can be done wothout the lock */
>> + while (n)
>> + put_page(pages[--n]);
>> +
>> + return ret;
>> +}
>> +
>> static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
>> - unsigned long size, int write)
>> + unsigned long size, int write)
>> {
>> struct vb2_dc_buf *buf;
>> - struct vm_area_struct *vma;
>> - dma_addr_t dma_addr = 0;
>> - int ret;
>> + unsigned long start, end, offset, offset2;
>> + struct page **pages;
>> + int n_pages;
>> + int ret = 0;
>> + struct sg_table *sgt;
>> + unsigned long contig_size;
>>
>> buf = kzalloc(sizeof *buf, GFP_KERNEL);
>> if (!buf)
>> return ERR_PTR(-ENOMEM);
>>
>> - ret = vb2_get_contig_userptr(vaddr, size, &vma, &dma_addr);
>> + buf->dev = alloc_ctx;
>> + buf->dma_dir = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
>> +
>> + start = (unsigned long)vaddr & PAGE_MASK;
>> + offset = (unsigned long)vaddr & ~PAGE_MASK;
>> + end = PAGE_ALIGN((unsigned long)vaddr + size);
>> + offset2 = end - (unsigned long)vaddr - size;
>> + n_pages = (end - start) >> PAGE_SHIFT;
>> +
>> + pages = kmalloc(n_pages * sizeof pages[0], GFP_KERNEL);
>> + if (!pages) {
>> + ret = -ENOMEM;
>> + printk(KERN_ERR "failed to allocate pages table\n");
>> + goto fail_buf;
>> + }
>> +
>> + /* extract page list from userspace mapping */
>> + ret = vb2_dc_get_pages(start, pages, n_pages, &buf->vma, write);
>> if (ret) {
>> - printk(KERN_ERR "Failed acquiring VMA for vaddr 0x%08lx\n",
>> - vaddr);
>> - kfree(buf);
>> - return ERR_PTR(ret);
>> + printk(KERN_ERR "failed to get user pages\n");
>> + goto fail_pages;
>> + }
>> +
>> + sgt = vb2_dc_pages_to_sgt(pages, n_pages, offset, offset2);
>> + if (!sgt) {
>> + printk(KERN_ERR "failed to create scatterlist table\n");
>> + ret = -ENOMEM;
>> + goto fail_get_pages;
>> }
>
> This looks overly complex to me. You create a multi-chunk sgt out of the user
> pointer address and map it completely, and then check if it starts with a big
> enough contiguous chunk.
Notice that vb2_dc_pages_to_sgt does compress contiguous ranges of pfns (pages).
So if the memory is contiguous, then sigle chunk sglist is produced.
The memory used to store pages list is just temporary. It is freed after the
sglist is created.
> Why don't you create an sgt with a single continuous
> chunk then ? In the VM_PFNMAP case you could check whether the area is
> contiguous when you follow the PFNs, stop at the first discontinuity, and
> create an sgt with a single element right there. You would then need to call
> vb2_dc_pages_to_sgt() in the normal case only, and stop at the first
> discontinuity as well.
Discontinuity of pfns is not a problem if a device has own IOMMU. It is not
known for vb2-dma-contig if mapping this multi-chunk sglist will succeed until
calling and checking a result of dma_map_sg.
Why bothering if both VM_PFNMAP and non-VM_PFNMAP are handled in the same way
after list of pages is obtained? Trating them the same way allows to reuse code
and simplify the program flow.
The DMA framework does not provide any way to force single chunk mapping in sg.
If the device is capable of mapping discontinous pages into a single chunk
the DMA framework will probably do merge the pages. The documentation
encourages to merge the list but it is not obligatory.
The reason is that if 'struct scatterlist' contains no dma_length field,
what is controlled by CONFIG_NEED_SG_DMA_LENGTH macro, then field length
is used instead. Chunk marging cannot be done in such a case.
This is the reason why I look for the longest contiguous block.
>
>>
>> + /* pages are no longer needed */
>> + kfree(pages);
>> + pages = NULL;
>> +
>> + sgt->nents = dma_map_sg(buf->dev, sgt->sgl, sgt->orig_nents,
>> + buf->dma_dir);
>> + if (sgt->nents <= 0) {
>> + printk(KERN_ERR "failed to map scatterlist\n");
>> + ret = -EIO;
>> + goto fail_sgt;
>> + }
>> +
>> + contig_size = vb2_dc_get_contiguous_size(sgt);
>> + if (contig_size < size) {
>> + printk(KERN_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->size = size;
>> - buf->dma_addr = dma_addr;
>> - buf->vma = vma;
>> + buf->dma_sgt = sgt;
>> +
>> + atomic_inc(&buf->refcount);
>>
>> return buf;
>> +
>> +fail_map_sg:
>> + dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
>
> I think this will break in the VM_PFNMAP case on non-coherent architectures.
> arm_dma_unmap_page() will call __dma_page_dev_to_cpu() in that case, which can
> dereference struct page. As explain above, the struct page isn't valid with
> VM_PFNMAP. I haven't check the dma_map_sg() and dma_sync_sg_*() calls, but
> changes are they might break as well.
>
It will crash as long it is true that there is no struct page behind given pfn.
In practice, I found that VM_PFNMAP means that one cannot assume that there is
a 'struct page' behind PFNs of a given mapping. Thoses struct pages really
exists for all our drivers. Anyway, I agree that using those pages is a hack.
It could be avoided if vb2_dc_get_pages returned a list of PFNs. Anyway, those PFNs
have to be transformed to pages to create an sglist. Those pointers might be
accessed somewhere deep inside dma_map_sg internals.
The quite good solution would be dropping support for VM_PFNMAP mappings since
they cannot be handled reliably.
>> +
>> +fail_sgt:
>> + vb2_dc_put_sgtable(sgt, 0);
>> +
>> +fail_get_pages:
>> + while (pages && n_pages)
>> + put_page(pages[--n_pages]);
>> + vb2_put_vma(buf->vma);
>> +
>> +fail_pages:
>> + kfree(pages); /* kfree is NULL-proof */
>> +
>> +fail_buf:
>> + kfree(buf);
>> +
>> + return ERR_PTR(ret);
>> }
>>
>> -static void vb2_dc_put_userptr(void *mem_priv)
>> +static void vb2_dc_put_userptr(void *buf_priv)
>> {
>> - struct vb2_dc_buf *buf = mem_priv;
>> -
>> - if (!buf)
>> - return;
>> + struct vb2_dc_buf *buf = buf_priv;
>> + struct sg_table *sgt = buf->dma_sgt;
>>
>> + dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
>> + vb2_dc_put_sgtable(sgt, !vma_is_io(buf->vma));
>> vb2_put_vma(buf->vma);
>> kfree(buf);
>> }
>> @@ -168,6 +496,8 @@ const struct vb2_mem_ops vb2_dma_contig_memops = {
>> .mmap = vb2_dc_mmap,
>> .get_userptr = vb2_dc_get_userptr,
>> .put_userptr = vb2_dc_put_userptr,
>> + .prepare = vb2_dc_prepare,
>> + .finish = vb2_dc_finish,
>> .num_users = vb2_dc_num_users,
>> };
>> EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
>
Regards,
Tomasz Stanislawski
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