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Diffstat (limited to 'drivers/dma-buf/dma-buf.c')
-rw-r--r--drivers/dma-buf/dma-buf.c63
1 files changed, 3 insertions, 60 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index ce41cd9b758a..d4097856c86b 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -878,29 +878,9 @@ EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
* with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
* access.
*
- * To support dma_buf objects residing in highmem cpu access is page-based
- * using an api similar to kmap. Accessing a dma_buf is done in aligned chunks
- * of PAGE_SIZE size. Before accessing a chunk it needs to be mapped, which
- * returns a pointer in kernel virtual address space. Afterwards the chunk
- * needs to be unmapped again. There is no limit on how often a given chunk
- * can be mapped and unmapped, i.e. the importer does not need to call
- * begin_cpu_access again before mapping the same chunk again.
- *
- * Interfaces::
- * void \*dma_buf_kmap(struct dma_buf \*, unsigned long);
- * void dma_buf_kunmap(struct dma_buf \*, unsigned long, void \*);
- *
- * Implementing the functions is optional for exporters and for importers all
- * the restrictions of using kmap apply.
- *
- * dma_buf kmap calls outside of the range specified in begin_cpu_access are
- * undefined. If the range is not PAGE_SIZE aligned, kmap needs to succeed on
- * the partial chunks at the beginning and end but may return stale or bogus
- * data outside of the range (in these partial chunks).
- *
- * For some cases the overhead of kmap can be too high, a vmap interface
- * is introduced. This interface should be used very carefully, as vmalloc
- * space is a limited resources on many architectures.
+ * Since for most kernel internal dma-buf accesses need the entire buffer, a
+ * vmap interface is introduced. Note that on very old 32-bit architectures
+ * vmalloc space might be limited and result in vmap calls failing.
*
* Interfaces::
* void \*dma_buf_vmap(struct dma_buf \*dmabuf)
@@ -1050,43 +1030,6 @@ int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
}
EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
-/**
- * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
- * same restrictions as for kmap and friends apply.
- * @dmabuf: [in] buffer to map page from.
- * @page_num: [in] page in PAGE_SIZE units to map.
- *
- * This call must always succeed, any necessary preparations that might fail
- * need to be done in begin_cpu_access.
- */
-void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
-{
- WARN_ON(!dmabuf);
-
- if (!dmabuf->ops->map)
- return NULL;
- return dmabuf->ops->map(dmabuf, page_num);
-}
-EXPORT_SYMBOL_GPL(dma_buf_kmap);
-
-/**
- * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
- * @dmabuf: [in] buffer to unmap page from.
- * @page_num: [in] page in PAGE_SIZE units to unmap.
- * @vaddr: [in] kernel space pointer obtained from dma_buf_kmap.
- *
- * This call must always succeed.
- */
-void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
- void *vaddr)
-{
- WARN_ON(!dmabuf);
-
- if (dmabuf->ops->unmap)
- dmabuf->ops->unmap(dmabuf, page_num, vaddr);
-}
-EXPORT_SYMBOL_GPL(dma_buf_kunmap);
-
/**
* dma_buf_mmap - Setup up a userspace mmap with the given vma