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Diffstat (limited to 'Documentation/core-api/dma-api.rst')
| -rw-r--r-- | Documentation/core-api/dma-api.rst | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst index 6d6d0edd2d27..829f20a193ca 100644 --- a/Documentation/core-api/dma-api.rst +++ b/Documentation/core-api/dma-api.rst @@ -206,6 +206,20 @@ others should not be larger than the returned value. :: + size_t + dma_opt_mapping_size(struct device *dev); + +Returns the maximum optimal size of a mapping for the device. + +Mapping larger buffers may take much longer in certain scenarios. In +addition, for high-rate short-lived streaming mappings, the upfront time +spent on the mapping may account for an appreciable part of the total +request lifetime. As such, if splitting larger requests incurs no +significant performance penalty, then device drivers are advised to +limit total DMA streaming mappings length to the returned value. + +:: + bool dma_need_sync(struct device *dev, dma_addr_t dma_addr); |