diff options
Diffstat (limited to 'drivers/dma-buf/dma-buf.c')
| -rw-r--r-- | drivers/dma-buf/dma-buf.c | 63 |
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 |