[PATCH 5/6] dmaengine: Add union and dma_slave_get_config() helper for dma_slave_config
From: Frank Li <Frank.Li@nxp.com>
Date: 2026-01-14 17:13:30
Also in:
dmaengine, imx, lkml
Subsystem:
dma generic offload engine subsystem, the rest · Maintainers:
Vinod Koul, Linus Torvalds
Previously, src_ and dst_ prefixes were used to distinguish address, addr_width, maxburst, and port_window_size fields. This required drivers to add conditional logic based on transfer direction. Introduce struct dma_slave_cfg to group these fields and add the dma_slave_get_config() helper to retrieve the source or destination configuration based on the DMA transfer direction. This reduces direction-based branching in drivers and improves readability. Use a union to preserve the old field naming and maintain compatibility. Signed-off-by: Frank Li <Frank.Li@nxp.com> --- include/linux/dmaengine.h | 42 ++++++++++++++++++++++++++++++++++-------- 1 file changed, 34 insertions(+), 8 deletions(-)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 362a43c3e36e232b5a65ff78ba0b692c0401e50c..03632bccc7ccb3c0c4a9c78f15865f35a375836a 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h@@ -384,21 +384,47 @@ enum dma_slave_buswidth { * If not: if it is fixed so that it be sent in static from the platform * data, then prefer to do that. */ +struct dma_slave_cfg { /* order must be align below dma_slave_config union */ + phys_addr_t addr; + enum dma_slave_buswidth addr_width; + u32 maxburst; + u32 port_window_size; +}; + struct dma_slave_config { enum dma_transfer_direction direction; - phys_addr_t src_addr; - phys_addr_t dst_addr; - enum dma_slave_buswidth src_addr_width; - enum dma_slave_buswidth dst_addr_width; - u32 src_maxburst; - u32 dst_maxburst; - u32 src_port_window_size; - u32 dst_port_window_size; + union { + struct { + phys_addr_t src_addr; + enum dma_slave_buswidth src_addr_width; + u32 src_maxburst; + u32 src_port_window_size; + phys_addr_t dst_addr; + enum dma_slave_buswidth dst_addr_width; + u32 dst_maxburst; + u32 dst_port_window_size; + }; + + struct { + struct dma_slave_cfg src; + struct dma_slave_cfg dst; + }; + }; bool device_fc; void *peripheral_config; size_t peripheral_size; }; +static inline struct dma_slave_cfg * +dma_slave_get_cfg(struct dma_slave_config *config, + enum dma_transfer_direction dir) +{ + if (dir == DMA_MEM_TO_DEV) + return &config->dst; + + return &config->src; +} + /** * struct dma_chan - devices supply DMA channels, clients use them * @device: ptr to the dma device who supplies this channel, always !%NULL
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2.34.1