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From: ayaka <ayaka@soulik.info>
To: kernelnewbies@kernelnewbies.org
Subject: CMA: why DMA_ATTR_FORCE_CONTIGUOUS is not used in v4l2 or DRM cma helper
Date: Fri, 11 Jun 2021 16:11:58 +0800	[thread overview]
Message-ID: <BDC4B95A-1991-46DB-88EE-671DE669E5EF@soulik.info> (raw)


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Hello All

I am looking for the CMA allocator in current kernel, when I check the videobuf2-dma-contig.c and drm_gem_cma_helper.c, they just call dma_alloc_wc()/dma_alloc_attrs() without any flag that request a contiguous pages.
I could hardly find a driver use the flag DMA_ATTR_FORCE_CONTIGUOUS, what I need to do if I want to allocate a CMA and DMA capable buffer for a driver(not all the buffers, because it may have a iommu in a different direction) ?

And anything I could that limit a driver that only allocate the pages for the DMA in a address base(for example only the low 4G memory) ?


Sincerely 
ayaka

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                 reply	other threads:[~2021-06-11  8:12 UTC|newest]

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