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Date:   Fri, 23 Apr 2021 18:54:59 +0530
From:   Vinod Koul <vkoul@kernel.org>
To:     Lars-Peter Clausen <lars@metafoo.de>
Cc:     Adrian Larumbe <adrian.martinezlarumbe@imgtec.com>,
        dmaengine@vger.kernel.org, michal.simek@xilinx.com,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/4] Expand Xilinx CDMA functions
Message-ID: <YILKq+jNZZSs37xa@vkoul-mobl.Dlink>
References: <20210423011913.13122-1-adrian.martinezlarumbe@imgtec.com>
 <c2876f2c-beb2-f159-9b61-d69ae6b8275a@metafoo.de>
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On 23-04-21, 11:17, Lars-Peter Clausen wrote:
> 
> It seems to me what we are missing from the DMAengine API is the equivalent
> of device_prep_dma_memcpy() that is able to take SG lists. There is already
> a memset_sg, it should be possible to add something similar for memcpy.

You mean something like dmaengine_prep_dma_sg() which was removed?

static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_sg(
               struct dma_chan *chan,
               struct scatterlist *dst_sg, unsigned int dst_nents,
               struct scatterlist *src_sg, unsigned int src_nents,
               unsigned long flags)

The problem with this API is that it would work only when src_sg and
dst_sg is of similar nature, if not then how should one go about
copying...should we fill without a care for dst_sg being different than
src_sg as long as total data to be copied has enough space in dst...

We can always add this back if we have in-kernel user but the semantics
of the API needs to be thought thru

Thanks
-- 
~Vinod