linux-kernel - Re: [PATCH v3 2/2] dma: add IOMMU static calls with clear default ops

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Message-ID: <20240722160555.GB7022@unreal>
Date: Mon, 22 Jul 2024 19:05:55 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Easwar Hariharan <eahariha@...ux.microsoft.com>,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	Jason Gunthorpe <jgg@...dia.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3 2/2] dma: add IOMMU static calls with clear default ops

On Mon, Jul 22, 2024 at 05:49:29PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 22, 2024 at 06:44:58PM +0300, Leon Romanovsky wrote:
> > On Mon, Jul 22, 2024 at 05:10:37PM +0200, Christoph Hellwig wrote:
> > > On Sun, Jul 21, 2024 at 10:49:11AM +0300, Leon Romanovsky wrote:
> > > > -static void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> > > > -		struct sg_table *sgt, enum dma_data_direction dir)
> > > > +void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> > > > +				  struct sg_table *sgt,
> > > > +				  enum dma_data_direction dir)
> > > 
> > > Why are you reformatting these to a much less readable coding style?
> > 
> > I'm relying on clang-formatter to format the code, see .clang-format
> > file in the kernel root directory.
> 
> Well, that uses a really horrible default then.  Aligning to the opening
> brace not only is hard to read, but requireѕ reformatting with every
> addition and removal of a static like here, or when trivially changing
> the function name.

Should I need to reformat the code to your preferred style?
I can do it, but it will be manual work :(.

> 
> > > > +static inline void dma_common_free_pages(struct device *dev, size_t size,
> > > > +					 struct page *vaddr,
> > > > +					 dma_addr_t dma_handle,
> > > > +					 enum dma_data_direction dir)
> > > > +{
> > > > +}
> > > 
> > > dma-iommu very much depends on these.  So we'll need to also
> > > build ops_helpers.o if dma-iommu is enabled.  So we'll probably need
> > > a separate Kconfig option for it that the various users select.
> > > 
> > 
> > I removed them from dma-iommu.c and there are no calls to them in that file.
> > ➜  kernel git:(m/dma-v2) git grep dma_common_alloc_pages drivers/iommu/ | wc -l
> 
> Well, you replaced them with direct calls from mapping.c, which now
> needs them if dma-iommu is supported.  So while strictly speaking
> dma-iommu doesn't need them, proper operation with dma-iommu still
> needs them.

No problem, I can add.

Thanks

>