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Date: Sun, 22 Sep 2024 16:32:06 +0200
From: Christoph Hellwig <hch@lst.de>
To: Leon Romanovsky <leon@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Robin Murphy <robin.murphy@arm.com>,
	iommu@lists.linux.dev, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Xi Ruoyao <xry111@xry111.site>
Subject: Re: [PATCH 2/2] iommu/dma: remove most stubs in iommu-dma.h
Message-ID: <20240922143206.GA16843@lst.de>
References: <20240922140743.1596763-1-hch@lst.de> <20240922140743.1596763-3-hch@lst.de> <20240922142819.GD11337@unreal>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Sun, Sep 22, 2024 at 05:28:19PM +0300, Leon Romanovsky wrote:
> On Sun, Sep 22, 2024 at 04:07:35PM +0200, Christoph Hellwig wrote:
> > The direct calls from mapping.c all guarded by use_dma_iommu(), so don't
> > bother to provide stubs, but instead just expose the prototypes
> > unconditionally.
> 
> I was afraid to do such a change because of fear that some compiler will
> call to the !CONFIG_IOMMU_DMA functions without checking the condition.

The kernel relies on this style of dead code elimination in many
places.  The IS_ENABLED() macro could not exist without it.