[PATCHv2 5/9] v4l: vb2-dma-contig: add support for DMABUF exporting
Tomasz Stanislawski
t.stanislaws at samsung.com
Thu Jun 14 07:32:25 PDT 2012
This patch adds support for exporting a dma-contig buffer using
DMABUF interface.
Signed-off-by: Tomasz Stanislawski <t.stanislaws at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
---
drivers/media/video/videobuf2-dma-contig.c | 248 ++++++++++++++++++++++++++++
1 file changed, 248 insertions(+)
diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c
index 00b776c..a845ff7 100644
--- a/drivers/media/video/videobuf2-dma-contig.c
+++ b/drivers/media/video/videobuf2-dma-contig.c
@@ -36,6 +36,7 @@ struct vb2_dc_buf {
/* MMAP related */
struct vb2_vmarea_handler handler;
atomic_t refcount;
+ struct sg_table *sgt_base;
/* USERPTR related */
struct vm_area_struct *vma;
@@ -142,6 +143,10 @@ static void vb2_dc_put(void *buf_priv)
if (!atomic_dec_and_test(&buf->refcount))
return;
+ if (buf->sgt_base) {
+ sg_free_table(buf->sgt_base);
+ kfree(buf->sgt_base);
+ }
dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr);
kfree(buf);
}
@@ -213,6 +218,248 @@ static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
}
/*********************************************/
+/* DMABUF ops for exporters */
+/*********************************************/
+
+struct vb2_dc_attachment {
+ struct sg_table sgt;
+ enum dma_data_direction 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->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->dir != DMA_NONE)
+ dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+ attach->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 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;
+ int ret;
+
+ mutex_lock(lock);
+
+ sgt = &attach->sgt;
+ /* return previously mapped sg table */
+ if (attach->dir == dir) {
+ mutex_unlock(lock);
+ return sgt;
+ }
+
+ /* release any previous cache */
+ if (attach->dir != DMA_NONE) {
+ dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+ attach->dir);
+ attach->dir = DMA_NONE;
+ }
+
+ /* mapping to the client with new direction */
+ ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dir);
+ if (ret <= 0) {
+ printk(KERN_ERR "failed to map scatterlist\n");
+ mutex_unlock(lock);
+ return ERR_PTR(-EIO);
+ }
+
+ attach->dir = 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 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 + pgnum * PAGE_SIZE;
+}
+
+static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
+{
+ struct vb2_dc_buf *buf = dbuf->priv;
+
+ return buf->vaddr;
+}
+
+static 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,
+ .kmap = vb2_dc_dmabuf_ops_kmap,
+ .kmap_atomic = vb2_dc_dmabuf_ops_kmap,
+ .vmap = vb2_dc_dmabuf_ops_vmap,
+ .release = vb2_dc_dmabuf_ops_release,
+};
+
+/**
+ * vb2_dc_kaddr_to_pages() - extract list of struct pages from a kernel
+ * pointer. This function is a workaround to extract pages from a pointer
+ * returned by dma_alloc_coherent. The pages are obtained by creating an
+ * artificial vma and using follow_pfn to do a page walk to find a PFN
+ */
+static int vb2_dc_kaddr_to_pages(unsigned long kaddr,
+ struct page **pages, unsigned int n_pages)
+{
+ unsigned int i;
+ unsigned long pfn;
+ /* create an artificial VMA */
+ struct vm_area_struct vma = {
+ .vm_flags = VM_IO | VM_PFNMAP,
+ .vm_mm = &init_mm,
+ };
+
+ for (i = 0; i < n_pages; ++i, kaddr += PAGE_SIZE) {
+ if (follow_pfn(&vma, kaddr, &pfn))
+ break;
+ pages[i] = pfn_to_page(pfn);
+ }
+
+ return i;
+}
+
+static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
+{
+ int n_pages;
+ struct page **pages = NULL;
+ int ret;
+ struct sg_table *sgt;
+
+ n_pages = PAGE_ALIGN(buf->size) >> PAGE_SHIFT;
+
+ pages = kmalloc(n_pages * sizeof pages[0], GFP_KERNEL);
+ if (!pages) {
+ dev_err(buf->dev, "failed to alloc page table\n");
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ret = vb2_dc_kaddr_to_pages((unsigned long)buf->vaddr, pages, n_pages);
+ if (ret < 0) {
+ dev_err(buf->dev, "failed to get buffer pages from DMA API\n");
+ kfree(pages);
+ return ERR_PTR(ret);
+ }
+ if (ret != n_pages) {
+ dev_err(buf->dev, "got only %d of %d pages from DMA API\n",
+ ret, n_pages);
+ kfree(pages);
+ return ERR_PTR(-EFAULT);
+ }
+
+ sgt = kmalloc(sizeof *sgt, GFP_KERNEL);
+ if (!sgt) {
+ dev_err(buf->dev, "failed to alloc sg table\n");
+ kfree(pages);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ret = sg_alloc_table_from_pages(sgt, pages, n_pages, 0,
+ buf->size, GFP_KERNEL);
+ /* failure or not, pages are no longer needed */
+ kfree(pages);
+ if (ret) {
+ dev_err(buf->dev, "failed to covert pages to sg table\n");
+ kfree(sgt);
+ return ERR_PTR(ret);
+ }
+
+ return sgt;
+}
+
+static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
+{
+ struct vb2_dc_buf *buf = buf_priv;
+ struct dma_buf *dbuf;
+ struct sg_table *sgt = buf->sgt_base;
+
+ if (!sgt)
+ sgt = vb2_dc_get_base_sgt(buf);
+ if (WARN_ON(IS_ERR(sgt)))
+ return NULL;
+
+ /* cache base sgt for future use */
+ buf->sgt_base = sgt;
+
+ dbuf = dma_buf_export(buf, &vb2_dc_dmabuf_ops, buf->size, 0);
+ if (IS_ERR(dbuf))
+ return NULL;
+
+ /* dmabuf keeps reference to vb2 buffer */
+ atomic_inc(&buf->refcount);
+
+ return dbuf;
+}
+
+/*********************************************/
/* callbacks for USERPTR buffers */
/*********************************************/
@@ -522,6 +769,7 @@ static void *vb2_dc_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf,
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,
--
1.7.9.5
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