lkml.org 
[lkml]   [2004]   [Jun]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH] dma_get_required_mask()
From
Date
Following the discussion, this is a patch implementing
dma_get_required_mask(). The default implementation simply works out
the largest mask covering all of memory and returns the and of that with
the current dma_mask. If this looks OK, I'll send out another patch
including the documentation updates as well.

I've put the implementation in linux/dma-mapping.h with a
ARCH_HAS_DMA_GET_REQUIRED_MASK override for those architectures that
would like to do something different.

Any opinions on whether I should also make linux/dma-mapping.h include
linux/bitops.h now since it requires fls() from there?

James

===== include/linux/dma-mapping.h 1.3 vs edited =====
--- 1.3/include/linux/dma-mapping.h 2004-03-30 20:53:54 -05:00
+++ edited/include/linux/dma-mapping.h 2004-06-25 11:12:30 -04:00
@@ -19,6 +19,29 @@
#define dma_sync_single dma_sync_single_for_cpu
#define dma_sync_sg dma_sync_sg_for_cpu

+#ifndef ARCH_HAS_DMA_GET_REQUIRED_MASK
+static inline u64 dma_get_required_mask(struct device *dev)
+{
+ extern unsigned long max_pfn; /* defined in bootmem.h but may
+ not be included */
+ u32 low_totalram = ((max_pfn - 1) << PAGE_SHIFT);
+ u32 high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT));
+ u64 mask;
+
+ if (!high_totalram) {
+ /* convert to mask just covering totalram */
+ low_totalram = (1 << (fls(low_totalram) - 1));
+ low_totalram += low_totalram - 1;
+ mask = low_totalram;
+ } else {
+ high_totalram = (1 << (fls(high_totalram) - 1));
+ high_totalram += high_totalram - 1;
+ mask = (((u64)high_totalram) << 32) + 0xffffffff;
+ }
+ return mask & *dev->dma_mask;
+}
+#endif
+
#endif


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:04    [from the cache]
©2003-2014 Jasper Spaans. hosted at Digital Ocean