Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751782AbdGEQWO (ORCPT ); Wed, 5 Jul 2017 12:22:14 -0400 Received: from foss.arm.com ([217.140.101.70]:58180 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751696AbdGEQWL (ORCPT ); Wed, 5 Jul 2017 12:22:11 -0400 Subject: Re: [RFC PATCH 4/5] iommu/dma: Export non-static functions to use in modules To: Tomasz Figa , iommu@lists.linux-foundation.org Cc: linux-kernel@vger.kernel.org, Christoph Hellwig , Marek Szyprowski , Greg Kroah-Hartman , Joerg Roedel , Will Deacon , Vineet Gupta , Hans-Christian Noren Egtvedt , Mitchel Humpherys , Krzysztof Kozlowski , Arnd Bergmann References: <20170705071215.17603-1-tfiga@chromium.org> <20170705071215.17603-5-tfiga@chromium.org> From: Robin Murphy Message-ID: Date: Wed, 5 Jul 2017 17:22:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20170705071215.17603-5-tfiga@chromium.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1948 Lines: 49 On 05/07/17 08:12, Tomasz Figa wrote: > There is nothing wrong in having a loadable module implementing DMA API, > for example to be used for sub-devices registered by the module. However, > most of the functions from dma-iommu do not have their symbols exported, > making it impossible to use them from loadable modules. > > Export all the non-static functions in the file, so that loadable modules > can benefit from them. Use EXPORT_SYMBOL() for consistency with other > exports in the file. To echo what Christoph said, everything not already exported here shouldn't in any way be considered a driver-facing API in the general sense, it's horrible glue code to sit behind an arch-specific DMA mapping implementation (and frankly I'd consider even the current exports more of an unfortunate abstraction leakage). > Signed-off-by: Tomasz Figa > --- [...] > @@ -829,17 +838,20 @@ dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, > return __iommu_dma_map(dev, phys, size, > dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO); > } > +EXPORT_SYMBOL(iommu_dma_map_resource); > > void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle, > size_t size, enum dma_data_direction dir, unsigned long attrs) > { > __iommu_dma_unmap(iommu_get_domain_for_dev(dev), handle, size); > } > +EXPORT_SYMBOL(iommu_dma_unmap_resource); Do you need these two? Unless your custom DMA ops really have to support slave DMA or other peer-to-peer traffic through their IOMMU, I'd be more inclined to implement dma_map_resource as "return 0;" and ignore dma_unmap_resource. > @@ -913,3 +925,4 @@ void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg) > msg->address_lo += lower_32_bits(msi_page->iova); > } > } > +EXPORT_SYMBOL(iommu_dma_map_msi_msg); Given the nature of the kind of irqchip drivers this exists for, the chances of one ever being modular seem vanishingly small. Robin.