Re: USB and DMA on Alpha with 2.6.0-test7

[David Brownell]

David Brownell wrote:
> The BUG_ON at include/asm-generic/dma-mapping.h:19 is a
> bug in that "generic DMA" code ... and I've seen the
> same BUG reported from PPC folk too.

Something like this should be correct even on x86, but
there may be some cases where a platform_dma_supported()
is necessary.

IMO this needs an all-architectures patch.  Not many
will need a platform_dma_supported() ... but almost
every implementation of that simple call is broken.

- Dave


--- 1.4/include/asm-generic/dma-mapping.h	Mon Jan 13 14:37:47 2003
+++ edited/include/asm-generic/dma-mapping.h	Fri Oct 10 10:53:25 2003
@@ -13,12 +13,13 @@
 /* need struct page definitions */
 #include <linux/mm.h>
 
+/* FIXME use this everywhere there's no platform_dma_supported() */
 static inline int
 dma_supported(struct device *dev, u64 mask)
 {
-	BUG_ON(dev->bus != &pci_bus_type);
-
-	return pci_dma_supported(to_pci_dev(dev), mask);
+	/* device can dma, using those address bits */
+	return dev->dma_mask
+		&& (mask & *dev->dma_mask) == *dev->dma_mask;
 }
 
 static inline int