Merge tag 'for-5.6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

[linux.git] / drivers / dma-buf / dma-buf.c

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index ce41cd9b758ac8fbaf22bc5c145ad9d93aac58f4..d4097856c86b8b4a93242e09095f6006fbb0c2ea 100644 (file)
--- 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