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Date: Mon, 16 Jun 2025 15:13:46 +0200
From: Christoph Hellwig <hch@lst.de>
To: James Clark <james.clark@linaro.org>
Cc: Christoph Hellwig <hch@lst.de>, Mark Brown <broonie@kernel.org>,
	olteanv@gmail.com, oe-kbuild-all@lists.linux.dev, arnd@arndb.de,
	larisa.grigore@nxp.com, Frank.li@nxp.com, linux-spi@vger.kernel.org,
	imx@lists.linux.dev, linux-kernel@vger.kernel.org,
	kernel test robot <lkp@intel.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>, iommu@lists.linux.dev
Subject: Re: [PATCH] dma-mapping: Stub out dma_{alloc,free,map}_pages() API
Message-ID: <20250616131346.GB29838@lst.de>
References: <202506160036.t9VDxF6p-lkp@intel.com> <20250616111749.316413-1-james.clark@linaro.org> <20250616112927.GA21689@lst.de> <5f1ca0ac-b66c-4b92-8f69-027c2468b117@sirena.org.uk> <20250616120832.GA24959@lst.de> <2d62254e-5cbe-4174-95d8-e80cae4f4543@sirena.org.uk> <20250616121444.GA25443@lst.de> <7cfcf919-3c7d-4f0c-911f-697ea3141080@linaro.org>
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On Mon, Jun 16, 2025 at 02:10:40PM +0100, James Clark wrote:
> The change introduces consistency with the existing declarations in 
> dma-mapping.h. Surely there is value in consistency and it doesn't do any 
> harm to define new ones with stubs the same as the other ones. That way 
> when you change an existing device that has DMA stuff to use a new part of 
> the API you don't have to predict that it will behave differently to 
> another part of the API.

Well, redoing the rest would definitively be nice, but so far no one
has signed up to that.

> I suppose it is possible to #ifdef out the DMA stuff in this driver, but 
> IMO it would be quite messy, and I don't think randomly not stubbing out 
> some functions is the right way to move towards fixing all the dependencies 
> in all drivers. We should continue with the stubs for now and fix whole 
> drivers one by one as a proper effort.

Does the driver even work at all without DMA support?