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b=MMRxE4R5dWVG/OvIS2VimVBlKeyDxFEF2K9D6swzKr75NtaOQPu3u1HzWpTwu+lSo 85SYMuWjDivh9mgJoWRmt7qwMovoZY3cNUlErSjiFU7xfzhO3L0mkCgYRIYpsXvOde 6bLpgXaPXrxvzY26yN0MVKUAc8tmb6/1to+m2Nu5CHHjLY2bKaY0s9yo80iAgyhCBS kpsv+ejCFSu6JJBaNiBYzlklGoRr29zyiIOS6p6yBFIJGxlp5B+VEhP9FbUdyO7D/F /3dZB82/joZZJZEPux6XkULpk+j2C6IsM2ZaXvYGa+K33lGdnm6E5zYBcY73gUMPBa AdQERFF7Kq6pg== Date: Fri, 8 Nov 2024 22:03:55 +0200 From: Leon Romanovsky To: Jonathan Corbet Cc: Jens Axboe , Jason Gunthorpe , Robin Murphy , Joerg Roedel , Will Deacon , Christoph Hellwig , Sagi Grimberg , Keith Busch , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , Marek Szyprowski , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v1 09/17] docs: core-api: document the IOVA-based API Message-ID: <20241108200355.GC189042@unreal> References: <881ef0bcf9aa971e995fbdd00776c5140a7b5b3d.1730298502.git.leon@kernel.org> <87ttchwmde.fsf@trenco.lwn.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ttchwmde.fsf@trenco.lwn.net> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1AE2940018 X-Stat-Signature: p7g4ytkzbsrndx5rm6upykeidx6418bo X-Rspam-User: X-HE-Tag: 1731096205-80531 X-HE-Meta: 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 WNxydZgs lzTnFBR5zzhzUzp+GU8APhNk72YwcfvUP/qJk5i6ghqiZs4AxoseYLfNgUH+FVunJbFEIvjXXerAyd6tq3TNIzyE/EV3O3eBpoLPL0vJc2VC3NKYu/PCCA4xsEJ8mW/DoZR354x2BZAmXd1eWh+rRYh0BeLyw4uQG2GlW4tgNW2eYQoDoVslDtefM2cCp0O5CoSLtNoeOnzWRs0d9zyVF1tfeQ4BWYsA7E7QujA/o20Jw+kL1yz+ZK1VteyQe5ypqNjT2BdkB7rb+cR97Smw3OC/TlsiETPyXhBxlmDVci47izmA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Nov 08, 2024 at 12:34:21PM -0700, Jonathan Corbet wrote: > Leon Romanovsky writes: > > > From: Christoph Hellwig > > > > Add an explanation of the newly added IOVA-based mapping API. > > > > Signed-off-by: Christoph Hellwig > > Signed-off-by: Leon Romanovsky > > --- > > Documentation/core-api/dma-api.rst | 70 ++++++++++++++++++++++++++++++ > > 1 file changed, 70 insertions(+) > > > > diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst > > index 8e3cce3d0a23..6095696a65a7 100644 > > --- a/Documentation/core-api/dma-api.rst > > +++ b/Documentation/core-api/dma-api.rst > > @@ -530,6 +530,76 @@ routines, e.g.::: > > .... > > } > > > > +Part Ie - IOVA-based DMA mappings > > +--------------------------------- > > + > > +These APIs allow a very efficient mapping when using an IOMMU. They are an > > +optional path that requires extra code and are only recommended for drivers > > +where DMA mapping performance, or the space usage for storing the DMA addresses > > +matter. All the consideration from the previous section apply here as well. > > + > > +:: > > + > > + bool dma_iova_try_alloc(struct device *dev, struct dma_iova_state *state, > > + phys_addr_t phys, size_t size); > > + > > +Is used to try to allocate IOVA space for mapping operation. If it returns > > +false this API can't be used for the given device and the normal streaming > > +DMA mapping API should be used. The ``struct dma_iova_state`` is allocated > > +by the driver and must be kept around until unmap time. > > So, I see that you have nice kernel-doc comments for these; why not just > pull them in here with a kernel-doc directive rather than duplicating > the information? Can I you please point me to commit/lore link/documentation with example of such directive and I will do it? Thanks > > Thanks, > > jon