[PATCH 1/6] swiotlb: Add helper to know if it is in use for a specific device.

[jglisse at redhat.com]

From: Jérôme Glisse <jglisse at redhat.com>

Some device like GPU do things differently if swiotlb is in use. We
use to rely on swiotlb_nr_tbl() to know if swiotlb was enabled or not
but this is unreliable. Patch add a simple helpers to check if any of
the dma_ops associated with a device points to the swiotlb functions,
making swiotlb check reliable for a device.

Signed-off-by: Jérôme Glisse <jglisse at redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: Dave Airlie <airlied at redhat.com>
Cc: lkml at vger.kernel.org
Cc: Daniel Vetter <daniel.vetter at intel.com>
---
 include/linux/dma-mapping.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ac07ff0..eac911e 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -314,4 +314,22 @@ static inline int dma_mmap_writecombine(struct device *dev,
 #define dma_unmap_len_set(PTR, LEN_NAME, VAL)    do { } while (0)
 #endif
 
+
+#ifdef CONFIG_SWIOTLB
+static inline bool swiotlb_in_use(struct device *dev)
+{
+	struct dma_map_ops *ops = get_dma_ops(dev);
+
+	return (ops->map_sg == swiotlb_map_sg_attrs ||
+		ops->unmap_sg == swiotlb_unmap_sg_attrs ||
+		ops->map_page == swiotlb_map_page);
+}
+#else
+static inline bool swiotlb_in_use(struct device *dev)
+{
+	return false;
+}
+#endif
+
+
 #endif
-- 
2.1.0