Messages in this thread | | | Subject | Re: [PATCH v2] staging: android: ion: Add implementation of dma_buf_vmap and dma_buf_vunmap | From | alexey <> | Date | Wed, 31 Jan 2018 01:44:47 +0200 |
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On 01/31/2018 12:15 AM, Greg KH wrote: > On Tue, Jan 30, 2018 at 10:39:13PM +0200, Alexey Skidanov wrote: >> dma_buf_vmap and dma_buf_vunmap allow drivers to access buffers, created by ion. > But why would anyone ever want to do that? What is wrong with the > existing interfaces that drivers use to access buffers created by ion? Any driver, sharing the buffers, created by ion, through dma-buf, may get back the sgtable describing the buffer for device DMA and may call dma_buf_vmap to get back the kernel virtual address of the buffer to get access to it. Currently, the second option is missing. Actually, the buffer already mapped by ion implementation. > What code uses this new interface? This is not the new interface. this is the missing implementation of the last two ops: struct dma_buf_ops { int (* attach) (struct dma_buf *, struct device *, struct dma_buf_attachment *); void (* detach) (struct dma_buf *, struct dma_buf_attachment *); struct sg_table * (* map_dma_buf) (struct dma_buf_attachment *, enum dma_data_direction); void (* unmap_dma_buf) (struct dma_buf_attachment *,struct sg_table *, enum dma_data_direction); void (* release) (struct dma_buf *); int (* begin_cpu_access) (struct dma_buf *, enum dma_data_direction); int (* end_cpu_access) (struct dma_buf *, enum dma_data_direction); void *(* map_atomic) (struct dma_buf *, unsigned long); void (* unmap_atomic) (struct dma_buf *, unsigned long, void *); void *(* map) (struct dma_buf *, unsigned long); void (* unmap) (struct dma_buf *, unsigned long, void *); int (* mmap) (struct dma_buf *, struct vm_area_struct *vma); void *(* vmap) (struct dma_buf *); void (* vunmap) (struct dma_buf *, void *vaddr); }; > > We need a bit more information please. > > thanks, > > greg k-h Thanks, Alexey
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