dma-direct: reject too small dma masks

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index 784a68dfdbe3..40b1f92f2214 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -122,6 +122,24 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
 	return nents;
 }
 
+int dma_direct_supported(struct device *dev, u64 mask)
+{
+#ifdef CONFIG_ZONE_DMA
+	if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
+		return 0;
+#else
+	/*
+	 * Because 32-bit DMA masks are so common we expect every architecture
+	 * to be able to satisfy them - either by not supporting more physical
+	 * memory, or by providing a ZONE_DMA32.  If neither is the case, the
+	 * architecture needs to use an IOMMU instead of the direct mapping.
+	 */
+	if (mask < DMA_BIT_MASK(32))
+		return 0;
+#endif
+	return 1;
+}
+
 static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
 	return dma_addr == DIRECT_MAPPING_ERROR;
@@ -132,6 +150,7 @@ const struct dma_map_ops dma_direct_ops = {
 	.free			= dma_direct_free,
 	.map_page		= dma_direct_map_page,
 	.map_sg			= dma_direct_map_sg,
+	.dma_supported		= dma_direct_supported,
 	.mapping_error		= dma_direct_mapping_error,
 };
 EXPORT_SYMBOL(dma_direct_ops);