Messages in this thread | | | Subject | Re: DMA-API attr - DMA_ATTR_NO_KERNEL_MAPPING | From | Robin Murphy <> | Date | Mon, 1 Jul 2019 18:54:47 +0100 |
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On 01/07/2019 18:47, Pankaj Suryawanshi wrote: >> If you want a kernel mapping, *don't* explicitly request not to have a >> kernel mapping in the first place. It's that simple. >> > > Do you mean do not use dma-api ? because if i used dma-api it will give you > mapped virtual address. > or i have to use directly cma_alloc() in my driver. // if i used this > approach i need to reserved more vmalloc area.
No, I mean just call dma_alloc_attrs() normally *without* adding the DMA_ATTR_NO_KERNEL_MAPPING flag. That flag means "I never ever want to make CPU accesses to this buffer from the kernel" - that is clearly not the case for your code, so it is utterly nonsensical to still pass the flag but try to hack around it later.
Robin.
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