dma-mapping: remove the {alloc,free}_noncoherent methods

It turns out allowing non-contigous allocations here was a rather bad
idea, as we'll now need to define ways to get the pages for mmaping
or dma_buf sharing.  Revert this change and stick to the original
concept.  A different API for the use case of non-contigous allocations
will be added back later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Tested-by: Ricardo Ribalda <ribalda@chromium.org>:wq

1 files changed, 22 insertions, 42 deletions

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index 75cb757bbff0..e6d23f117308 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -528,16 +528,14 @@ an I/O device, you should not be using this part of the API.
 
 ::
 
-	void *
-	dma_alloc_noncoherent(struct device *dev, size_t size,
-			dma_addr_t *dma_handle, enum dma_data_direction dir,
-			gfp_t gfp)
+	struct page *
+	dma_alloc_pages(struct device *dev, size_t size, dma_addr_t *dma_handle,
+			enum dma_data_direction dir, gfp_t gfp)
 
-This routine allocates a region of <size> bytes of consistent memory.  It
-returns a pointer to the allocated region (in the processor's virtual address
-space) or NULL if the allocation failed.  The returned memory may or may not
-be in the kernel direct mapping.  Drivers must not call virt_to_page on
-the returned memory region.
+This routine allocates a region of <size> bytes of non-coherent memory.  It
+returns a pointer to first struct page for the region, or NULL if the
+allocation failed. The resulting struct page can be used for everything a
+struct page is suitable for.
 
 It also returns a <dma_handle> which may be cast to an unsigned integer the
 same width as the bus and given to the device as the DMA address base of
@@ -558,51 +556,33 @@ reused.
 ::
 
 	void
-	dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr,
+	dma_free_pages(struct device *dev, size_t size, struct page *page,
 			dma_addr_t dma_handle, enum dma_data_direction dir)
 
-Free a region of memory previously allocated using dma_alloc_noncoherent().
-dev, size and dma_handle and dir must all be the same as those passed into
-dma_alloc_noncoherent().  cpu_addr must be the virtual address returned by
-dma_alloc_noncoherent().
+Free a region of memory previously allocated using dma_alloc_pages().
+dev, size, dma_handle and dir must all be the same as those passed into
+dma_alloc_pages().  page must be the pointer returned by dma_alloc_pages().
 
 ::
 
-	struct page *
-	dma_alloc_pages(struct device *dev, size_t size, dma_addr_t *dma_handle,
-			enum dma_data_direction dir, gfp_t gfp)
-
-This routine allocates a region of <size> bytes of non-coherent memory.  It
-returns a pointer to first struct page for the region, or NULL if the
-allocation failed. The resulting struct page can be used for everything a
-struct page is suitable for.
-
-It also returns a <dma_handle> which may be cast to an unsigned integer the
-same width as the bus and given to the device as the DMA address base of
-the region.
-
-The dir parameter specified if data is read and/or written by the device,
-see dma_map_single() for details.
-
-The gfp parameter allows the caller to specify the ``GFP_`` flags (see
-kmalloc()) for the allocation, but rejects flags used to specify a memory
-zone such as GFP_DMA or GFP_HIGHMEM.
+	void *
+	dma_alloc_noncoherent(struct device *dev, size_t size,
+			dma_addr_t *dma_handle, enum dma_data_direction dir,
+			gfp_t gfp)
 
-Before giving the memory to the device, dma_sync_single_for_device() needs
-to be called, and before reading memory written by the device,
-dma_sync_single_for_cpu(), just like for streaming DMA mappings that are
-reused.
+This routine is a convenient wrapper around dma_alloc_pages that returns the
+kernel virtual address for the allocated memory instead of the page structure.
 
 ::
 
 	void
-	dma_free_pages(struct device *dev, size_t size, struct page *page,
+	dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr,
 			dma_addr_t dma_handle, enum dma_data_direction dir)
 
-Free a region of memory previously allocated using dma_alloc_pages().
-dev, size and dma_handle and dir must all be the same as those passed into
-dma_alloc_noncoherent().  page must be the pointer returned by
-dma_alloc_pages().
+Free a region of memory previously allocated using dma_alloc_noncoherent().
+dev, size, dma_handle and dir must all be the same as those passed into
+dma_alloc_noncoherent().  cpu_addr must be the virtual address returned by
+dma_alloc_noncoherent().
 
 ::