On Sat, 2016-01-02 at 19:35 +0100, Mike Looijmans wrote:

On 2-1-2016 11:39, Russell King - ARM Linux wrote:

quoted

On Thu, Dec 31, 2015 at 04:50:54PM +0900, Masahiro Yamada wrote:

quoted

Hi.

I am new to the Linux DMA APIs.

First, I started by reading Documentation/DMA-API.txt,
but I am confused with the term "consistent memory".

Just read "coherent memory" instead - the documentation confusingly
uses
the two terms to refer to the same thing.  I think there was a
patch a
while back to replace "consistent" with "coherent" in this
document,
though I'm not sure what happened to it.

I wrote that patch. I never got any comments on it, so either I
didn't 
post it to the right people, or no one really cares:
http://www.kernelhub.org/?msg=747166&p=2

I still think that if the kernel methods all have "coherent" in their
name, we should use the word "coherent" in the documentation as well,
and not confuse people even further. So I'd happily repost that 
patch.

They don't: the PCI API still uses consistent:

asm-generic/pci-dma-compat.h:pci_alloc_consistent(struct pci_dev *hwdev, size_t size,
asm-generic/pci-dma-compat.h:pci_zalloc_consistent(struct pci_dev *hwdev, size_t size,
asm-generic/pci-dma-compat.h:pci_free_consistent(struct pci_dev *hwdev, size_t size,
asm-generic/pci-dma-compat.h:static inline int pci_set_consistent_dma_mask(struct pci_dev *dev, u64 mask)
linux/pci.h:/* kmem_cache style wrapper around pci_alloc_consistent() */
linux/pci.h:static inline int pci_set_consistent_dma_mask(struct pci_dev *dev, u64 mask)

These are named based on the PCI specification.

James