Re: [Linaro-mm-sig] [PATCHv5 08/13] v4l: vb2-dma-contig: add support for scatterlist in userptr mode

Hello Thomasz, Laurent,

I found an issue in the function vb2_dc_pages_to_sgt() below. I saw that during the attach, the size of the SGT and size requested mis-matched (by atleast 8k bytes). Hence I made a small correction to the code as below. I could then attach the importer properly.

Regards, Subash

On 04/20/2012 08:15 PM, Tomasz Stanislawski wrote:

From: Andrzej Pietrasiewiczandrzej.p@samsung.com

This patch introduces usage of dma_map_sg to map memory behind a userspace pointer to a device as dma-contiguous mapping.

Signed-off-by: Andrzej Pietrasiewiczandrzej.p@samsung.com Signed-off-by: Marek Szyprowskim.szyprowski@samsung.com [bugfixing] Signed-off-by: Kamil Debskik.debski@samsung.com [bugfixing] Signed-off-by: Tomasz Stanislawskit.stanislaws@samsung.com [add sglist subroutines/code refactoring] Signed-off-by: Kyungmin Parkkyungmin.park@samsung.com

---

drivers/media/video/videobuf2-dma-contig.c | 279 ++++++++++++++++++++++++++-- 1 files changed, 262 insertions(+), 17 deletions(-)

diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c index 476e536..9cbc8d4 100644 --- a/drivers/media/video/videobuf2-dma-contig.c +++ b/drivers/media/video/videobuf2-dma-contig.c @@ -11,6 +11,8 @@ */

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

@@ -22,6 +24,8 @@ struct vb2_dc_buf { void *vaddr; unsigned long size; dma_addr_t dma_addr;

• enum dma_data_direction dma_dir;

• struct sg_table *dma_sgt;

  /* MMAP related */ struct vb2_vmarea_handler handler;

@@ -32,6 +36,95 @@ struct vb2_dc_buf { };

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

+static struct sg_table *vb2_dc_pages_to_sgt(struct page **pages,

• unsigned int n_pages, unsigned long offset, unsigned long size)

+{

• struct sg_table *sgt;
• unsigned int chunks;
• unsigned int i;
• unsigned int cur_page;
• 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) {

• unsigned long chunk_size;
  

• unsigned int j;
  

size = PAGE_SIZE;

• for (j = cur_page + 1; j<  n_pages; ++j)
  

for (j = cur_page + 1; j < n_pages; ++j) {

• 	if (pages[j] != pages[j - 1] + 1)
  

• 		break;
  

size += PAGE }

• chunk_size = ((j - cur_page)<<  PAGE_SHIFT) - offset;
  

• sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
  

[DELETE] size -= chunk_size;

• 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_sgt_foreach_page(struct sg_table *sgt,

• void (*cb)(struct page *pg))

+{

• struct scatterlist *s;
• unsigned int i;
• for_each_sg(sgt->sgl, s, sgt->nents, i) {

• struct page *page = sg_page(s);
  

• unsigned int n_pages = PAGE_ALIGN(s->offset + s->length)
  

• 	>>  PAGE_SHIFT;
  

• unsigned int j;
  

• for (j = 0; j<  n_pages; ++j, ++page)
  

• 	cb(page);
  

• }

+}

+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 */ /*********************************************/

@@ -116,42 +209,194 @@ static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma) /* callbacks for USERPTR buffers */ /*********************************************/

+static inline int vma_is_io(struct vm_area_struct *vma) +{

• return !!(vma->vm_flags& (VM_IO | VM_PFNMAP));

+}

+static struct vm_area_struct *vb2_dc_get_user_vma(

• unsigned long start, unsigned long size)

+{

• struct vm_area_struct *vma;
• /* current->mm->mmap_sem is taken by videobuf2 core */
• vma = find_vma(current->mm, start);
• if (!vma) {

• printk(KERN_ERR "no vma for address %lu\n", start);
  

• return ERR_PTR(-EFAULT);
  

• }
• if (vma->vm_end - vma->vm_start< size) {

• printk(KERN_ERR "vma at %lu is too small for %lu bytes\n",
  

• 	start, size);
  

• return ERR_PTR(-EFAULT);
  

• }
• vma = vb2_get_vma(vma);
• if (!vma) {

• printk(KERN_ERR "failed to copy vma\n");
  

• return ERR_PTR(-ENOMEM);
  

• }
• return vma;

+}

+static int vb2_dc_get_user_pages(unsigned long start, struct page **pages,

• int n_pages, struct vm_area_struct *vma, int write)

+{

• if (vma_is_io(vma)) {

• unsigned int i;
  

• for (i = 0; i<  n_pages; ++i, start += PAGE_SIZE) {
  

• 	unsigned long pfn;
  

• 	int ret = follow_pfn(vma, start,&pfn);
  

• 	if (ret) {
  

• 		printk(KERN_ERR "no page for address %lu\n",
  

• 			start);
  

• 		return ret;
  

• 	}
  

• 	pages[i] = pfn_to_page(pfn);
  

• }
  

• } else {

• unsigned int n;
  

• 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);
  

• 	while (n)
  

• 		put_page(pages[--n]);
  

• 	return -EFAULT;
  

• }
  

• }
• return 0;

+}

+static void vb2_dc_put_dirty_page(struct page *page) +{

• set_page_dirty_lock(page);
• put_page(page);

+}

+static void vb2_dc_put_userptr(void *buf_priv) +{

• 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);
• if (!vma_is_io(buf->vma))

• vb2_dc_sgt_foreach_page(sgt, vb2_dc_put_dirty_page);
  

• vb2_dc_release_sgtable(sgt);
• vb2_put_vma(buf->vma);
• kfree(buf);

+}

• 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;

• unsigned long end;

• unsigned long offset;

• 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 = vaddr& PAGE_MASK;
• offset = vaddr& ~PAGE_MASK;
• end = PAGE_ALIGN(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;
  

• }
• buf->vma = vb2_dc_get_user_vma(start, size);
• if (IS_ERR(buf->vma)) {

• printk(KERN_ERR "failed to get VMA\n");
  

• ret = PTR_ERR(buf->vma);
  

• goto fail_pages;
  

• }
• /* extract page list from userspace mapping */
• ret = vb2_dc_get_user_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_vma;
  

• }

• sgt = vb2_dc_pages_to_sgt(pages, n_pages, offset, size);

• if (IS_ERR(sgt)) {

• printk(KERN_ERR "failed to create scatterlist table\n");
  

• ret = -ENOMEM;
  

• goto fail_get_user_pages;
  

• }

• /* 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;

  return buf;

-}

-static void vb2_dc_put_userptr(void *mem_priv) -{

• struct vb2_dc_buf *buf = mem_priv;

+fail_map_sg:

• dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);

• if (!buf)

• return;
  

+fail_sgt:

• if (!vma_is_io(buf->vma))

• vb2_dc_sgt_foreach_page(sgt, put_page);
  

• vb2_dc_release_sgtable(sgt);

+fail_get_user_pages:

• if (pages&& !vma_is_io(buf->vma))

• while (n_pages)
  

• 	put_page(pages[--n_pages]);
  
  

+fail_vma: vb2_put_vma(buf->vma);

+fail_pages:

• kfree(pages); /* kfree is NULL-proof */

+fail_buf: kfree(buf);

• return ERR_PTR(ret); }

  /*********************************************/