linux-kernel - Re: [PATCH 2/2] kernel/dma: rename dma_alloc_direct and dma_map

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Message-ID: <20220222155947.GB13323@lst.de>
Date:   Tue, 22 Feb 2022 16:59:47 +0100
From:   Christoph Hellwig <hch@....de>
To:     Baoquan He <bhe@...hat.com>
Cc:     Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org, cl@...ux.com,
        42.hyeyoo@...il.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, vbabka@...e.cz, David.Laight@...lab.com,
        david@...hat.com, herbert@...dor.apana.org.au, davem@...emloft.net,
        linux-crypto@...r.kernel.org, steffen.klassert@...unet.com,
        netdev@...r.kernel.org, hca@...ux.ibm.com, gor@...ux.ibm.com,
        agordeev@...ux.ibm.com, borntraeger@...ux.ibm.com,
        svens@...ux.ibm.com, linux-s390@...r.kernel.org, michael@...le.cc,
        linux-i2c@...r.kernel.org, wsa@...nel.org
Subject: Re: [PATCH 2/2] kernel/dma: rename dma_alloc_direct and
 dma_map_direct

On Tue, Feb 22, 2022 at 09:42:22PM +0800, Baoquan He wrote:
> In the old dma mapping, coherent mapping uses dma_alloc_coherent() to
> allocate DMA buffer and mapping; while streaming mapping can only get
> memory from slab or buddy allocator, then map with dma_map_single().
> In that situation, dma_alloc_direct() checks a direct mapping for
> coherent DMA, dma_map_direct() checks a direct mapping for streaming
> DMA.
> 
> However, several new APIs have been added for streaming mapping, e.g
> dma_alloc_pages(). These new APIs take care of DMA buffer allocating
> and mapping which are similar with dma_alloc_coherent(). So we should
> rename both of them to reflect their real intention to avoid confusion.
> 
>        dma_alloc_direct()  ==>  dma_coherent_direct()
>        dma_map_direct()    ==>  dma_streaming_direct()

No, these new names are highly misleading.