[PATCHv6 08/13] v4l: vb2-dma-contig: add support for scatterlist in userptr mode
Tomasz Stanislawski
t.stanislaws at samsung.com
Wed May 23 05:10:22 PDT 2012
This patch introduces usage of dma_map_sg to map memory behind
a userspace pointer to a device as dma-contiguous mapping.
This patch contains some of the code kindly provided by Marek Szyprowski
<m.szyprowski at samsung.com> and Kamil Debski <k.debski at samsung.com> and Andrzej
Pietrasiewicz <andrzej.p at samsung.com>. Kind thanks for bug reports from Laurent
Pinchart <laurent.pinchart at ideasonboard.com> and Seung-Woo Kim
<sw0312.kim at samsung.com>.
Signed-off-by: Tomasz Stanislawski <t.stanislaws at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
drivers/media/video/videobuf2-dma-contig.c | 268 ++++++++++++++++++++++++++--
1 file changed, 252 insertions(+), 16 deletions(-)
diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c
index 42c6431..068ec11 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>
@@ -23,6 +25,8 @@ 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;
@@ -33,6 +37,95 @@ 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;
+
+ for (j = cur_page + 1; j < n_pages; ++j)
+ if (pages[j] != pages[j - 1] + 1)
+ break;
+
+ chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
+ sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
+ 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 */
/*********************************************/
@@ -117,42 +210,185 @@ 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 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 {
+ int n;
+
+ n = get_user_pages(current, current->mm, start & PAGE_MASK,
+ n_pages, write, 1, pages, NULL);
+ /* negative error means that no page was pinned */
+ n = max(n, 0);
+ 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;
+ unsigned long start;
+ unsigned long end;
+ unsigned long offset;
+ struct page **pages;
+ int n_pages;
+ int ret = 0;
struct vm_area_struct *vma;
- dma_addr_t dma_addr = 0;
- int ret;
+ 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;
+ }
+
+ /* current->mm->mmap_sem is taken by videobuf2 core */
+ vma = find_vma(current->mm, vaddr);
+ if (!vma) {
+ printk(KERN_ERR "no vma for address %lu\n", vaddr);
+ ret = -EFAULT;
+ goto fail_pages;
+ }
+
+ if (vma->vm_end < vaddr + size) {
+ printk(KERN_ERR "vma at %lu is too small for %lu bytes\n",
+ vaddr, size);
+ ret = -EFAULT;
+ goto fail_pages;
+ }
+
+ buf->vma = vb2_get_vma(vma);
+ if (!buf->vma) {
+ printk(KERN_ERR "failed to copy vma\n");
+ ret = -ENOMEM;
+ goto fail_pages;
+ }
+
+ /* extract page list from userspace mapping */
+ ret = vb2_dc_get_user_pages(start, pages, n_pages, 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);
}
/*********************************************/
--
1.7.9.5
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