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@@ -293,6 +293,17 @@ Access to a dma_buf from the kernel context involves three steps:
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Note that these calls need to always succeed. The exporter needs to complete
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any preparations that might fail in begin_cpu_access.
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+ For some cases the overhead of kmap can be too high, a vmap interface
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+ is introduced. This interface should be used very carefully, as vmalloc
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+ space is a limited resources on many architectures.
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+
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+ Interfaces:
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+ void *dma_buf_vmap(struct dma_buf *dmabuf)
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+ void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
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+
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+ The vmap call can fail if there is no vmap support in the exporter, or if it
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+ runs out of vmalloc space. Fallback to kmap should be implemented.
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+
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3. Finish access
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When the importer is done accessing the range specified in begin_cpu_access,
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Dave Airlie