The patch titled
Update DMA-mapping documentation
has been added to the -mm tree. Its filename is
update-dma-mapping-documentation.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Update DMA-mapping documentation
From: Matthew Wilcox <matthew@xxxxxx>
A couple of updates haven't considered whether the documentation makes
sense as a whole any more. Three changes here:
- Remove the reference to the "DAC Addressing for Address Space Hungry
Devices" section which was deleted by Jan Beulich.
- Remove the comment about DMA_24BIT_MASK which became obsolete when
Tobias Klauser changed the code to actually use DMA_24BIT_MASK.
- Remove the section "64-bit DMA and DAC cycle support" since it's
fully covered above, and contains a reference to the section deleted
by Jan.
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN Documentation/DMA-mapping.txt~update-dma-mapping-documentation Documentation/DMA-mapping.txt
--- a/Documentation/DMA-mapping.txt~update-dma-mapping-documentation
+++ a/Documentation/DMA-mapping.txt
@@ -189,12 +189,6 @@ smaller mask as pci_set_dma_mask(). Howe
device driver only uses consistent allocations, one would have to
check the return value from pci_set_consistent_dma_mask().
-If your 64-bit device is going to be an enormous consumer of DMA
-mappings, this can be problematic since the DMA mappings are a
-finite resource on many platforms. Please see the "DAC Addressing
-for Address Space Hungry Devices" section near the end of this
-document for how to handle this case.
-
Finally, if your device can only drive the low 24-bits of
address during PCI bus mastering you might do something like:
@@ -203,8 +197,6 @@ address during PCI bus mastering you mig
"mydev: 24-bit DMA addressing not available.\n");
goto ignore_this_device;
}
-[Better use DMA_24BIT_MASK instead of 0x00ffffff.
-See linux/include/dma-mapping.h for reference.]
When pci_set_dma_mask() is successful, and returns zero, the PCI layer
saves away this mask you have provided. The PCI layer will use this
@@ -652,18 +644,6 @@ It is planned to completely remove virt_
they are entirely deprecated. Some ports already do not provide these
as it is impossible to correctly support them.
- 64-bit DMA and DAC cycle support
-
-Do you understand all of the text above? Great, then you already
-know how to use 64-bit DMA addressing under Linux. Simply make
-the appropriate pci_set_dma_mask() calls based upon your cards
-capabilities, then use the mapping APIs above.
-
-It is that simple.
-
-Well, not for some odd devices. See the next section for information
-about that.
-
Optimizing Unmap State Space Consumption
On many platforms, pci_unmap_{single,page}() is simply a nop.
_
Patches currently in -mm which might be from matthew@xxxxxx are
git-scsi-misc.patch
update-dma-mapping-documentation.patch
make-sure-nobodys-leaking-resources.patch
-
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