This patch adds support for exporting a dma-contig buffer using DMABUF interface.
Signed-off-by: Tomasz Stanislawski t.stanislaws@samsung.com Signed-off-by: Kyungmin Park kyungmin.park@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,