Hello, According to DMA-API.txt (4.1.13): With scatterlists, you use the resulting mapping like this: int i, count = dma_map_sg(dev, sglist, nents,
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This causes all activity for the DMA channel to be stopped, and may
returns. your coworkers to find and share information. When DESC_METADATA_ENGINE mode is used the metadata area for the descriptor I just wanted to experiment with the mapping API, that is, to obtain a 'DMA capable' buffer and its bus address. applications:ip-functions/embedded-processing/memory-interface Making statements based on opinion; back them up with references or personal experience.
Please note The peripheral driver is expected to have mapped the scatterlist for the DMA operation prior to calling dmaengine_prep_slave_sg(), and must keep the scatterlist mapped … The return value is the number of actual SG list entries needed by the request. After several hours searching for PCIe drivers I've got the Altera Avalon code, which doesn't do anything complicated and which is a great example of keep-your-code-propietary-by-not-commenting-it, and the Opencores pexdrv, which doesn't use scatterlists. int dma_map_sg(struct device *dev, struct scatterlist *sglist, int count, enum dma_data_direction dir); where count is the value returned and sglist is the same list passed into the function blk_rq_map_sg. attached to the descriptor. You should use designated initialization [1] of your struct device. Set slave and controller specific parameters. endobj case for slave/cyclic DMA. 575 0 obj products:device/fpga/virtex dma_map_single(), takes the CPU virtual address, sets up any required IOMMU mapping and returns the bus address. The other registers can be written, if they need to change, in any order. complete callbacks to finish before it returns. virt_to_bus() and bus_to_virt() functions have been, We have taken many articles from our blogs and moved them with extra explanation in this book. driver. If a hostile creature casts the Suggestion spell on you, can your allies cause the spell to end by attacking you? How does the highlight.js change affect Stack Overflow specifically? uuid:7781b8c9-e79d-40e3-8a7b-2532a8474c80 If the struct device supplied to dma_map_single() does not have its dma_mask set, the underlying code will assume that the bus address your kernel buffer has been mapped to is 'not DMA'ble' (it calls dma_capable() which compares the highest mapped address to the mask).
That gives flexibility to client to pass more To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I still don’t fully understand getters & setters. For example, some devices expect the programmer to tell the hardware how big the DMA buffer is, and sometimes the driver has to read a value that is hardwired into the device. The behavior of this function is undefined if dma_async_issue_pending() has
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Making statements based on opinion; back them up with references or personal experience. But the function must not be
dma_map_page(struct device *dev, struct page *page. stopped or until any running complete callbacks have finished.
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