From a92df4f62fda02e6b141e2b0bb52ccc486264b1c Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 18 Aug 2020 19:32:42 +0200 Subject: dma-mapping: move the dma_declare_coherent_memory documentation dma_declare_coherent_memory should not be in a DMA API guide aimed at driver writers (that is consumers of the API). Move it to a comment near the function instead. Signed-off-by: Christoph Hellwig Reviewed-by: Robin Murphy --- kernel/dma/coherent.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'kernel/dma') diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c index 2a0c4985f38e..f85d14bbfcbe 100644 --- a/kernel/dma/coherent.c +++ b/kernel/dma/coherent.c @@ -107,6 +107,23 @@ static int dma_assign_coherent_memory(struct device *dev, return 0; } +/* + * Declare a region of memory to be handed out by dma_alloc_coherent() when it + * is asked for coherent memory for this device. This shall only be used + * from platform code, usually based on the device tree description. + * + * phys_addr is the CPU physical address to which the memory is currently + * assigned (this will be ioremapped so the CPU can access the region). + * + * device_addr is the DMA address the device needs to be programmed with to + * actually address this memory (this will be handed out as the dma_addr_t in + * dma_alloc_coherent()). + * + * size is the size of the area (must be a multiple of PAGE_SIZE). + * + * As a simplification for the platforms, only *one* such region of memory may + * be declared per device. + */ int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr, dma_addr_t device_addr, size_t size) { -- cgit v1.2.3