[PATCH v3 4/7] media: vb2-dma-contig: add helper for setting dma max seg size

[Marek Szyprowski <m.szyprowski@samsung.com>]

Add a helper function for device drivers to set DMA's max_seg_size.
Setting it to largest possible value lets DMA-mapping API always create
contiguous mappings in DMA address space. This is essential for all
devices, which use dma-contig videobuf2 memory allocator and shared
buffers.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 14 ++++++++++++++
 include/media/videobuf2-dma-contig.h           |  1 +
 2 files changed, 15 insertions(+)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index c33127284cfe..bd893788d1ae 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -742,6 +742,20 @@ void vb2_dma_contig_cleanup_ctx(void *alloc_ctx)
 }
 EXPORT_SYMBOL_GPL(vb2_dma_contig_cleanup_ctx);
 
+int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
+{
+	if (!dev->dma_parms) {
+		dev->dma_parms = kzalloc(sizeof(dev->dma_parms), GFP_KERNEL);
+		if (!dev->dma_parms)
+			return -ENOMEM;
+	}
+	if (dma_get_max_seg_size(dev) < size)
+		return dma_set_max_seg_size(dev, size);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
+
 MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
 MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
 MODULE_LICENSE("GPL");
diff --git a/include/media/videobuf2-dma-contig.h b/include/media/videobuf2-dma-contig.h
index c33dfa69d7ab..0e6ba644939e 100644
--- a/include/media/videobuf2-dma-contig.h
+++ b/include/media/videobuf2-dma-contig.h
@@ -26,6 +26,7 @@ vb2_dma_contig_plane_dma_addr(struct vb2_buffer *vb, unsigned int plane_no)
 
 void *vb2_dma_contig_init_ctx(struct device *dev);
 void vb2_dma_contig_cleanup_ctx(void *alloc_ctx);
+int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size);
 
 extern const struct vb2_mem_ops vb2_dma_contig_memops;
 
-- 
1.9.2