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Received: from clnet-p099-196.ikbnet.co.at ([83.175.99.196] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.87 #1 (Red Hat Linux)) id 1dLvja-00060v-0U; Fri, 16 Jun 2017 18:12:38 +0000 From: Christoph Hellwig To: x86@kernel.org, linux-arm-kernel@lists.infradead.org, xen-devel@lists.xenproject.org, linux-c6x-dev@linux-c6x.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@linux-mips.org, openrisc@lists.librecores.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, iommu@lists.linux-foundation.org, netdev@vger.kernel.org Date: Fri, 16 Jun 2017 20:10:41 +0200 Message-Id: <20170616181059.19206-27-hch@lst.de> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170616181059.19206-1-hch@lst.de> References: <20170616181059.19206-1-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Cc: linux-kernel@vger.kernel.org Subject: [Xen-devel] [PATCH 26/44] dma-mapping: remove DMA_ERROR_CODE X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP And update the documentation - dma_mapping_error has been supported everywhere for a long time. Signed-off-by: Christoph Hellwig --- Documentation/DMA-API-HOWTO.txt | 31 +++++-------------------------- include/linux/dma-mapping.h | 5 ----- 2 files changed, 5 insertions(+), 31 deletions(-) diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt index 979228bc9035..4ed388356898 100644 --- a/Documentation/DMA-API-HOWTO.txt +++ b/Documentation/DMA-API-HOWTO.txt @@ -550,32 +550,11 @@ and to unmap it: dma_unmap_single(dev, dma_handle, size, direction); You should call dma_mapping_error() as dma_map_single() could fail and return -error. Not all DMA implementations support the dma_mapping_error() interface. -However, it is a good practice to call dma_mapping_error() interface, which -will invoke the generic mapping error check interface. Doing so will ensure -that the mapping code will work correctly on all DMA implementations without -any dependency on the specifics of the underlying implementation. Using the -returned address without checking for errors could result in failures ranging -from panics to silent data corruption. A couple of examples of incorrect ways -to check for errors that make assumptions about the underlying DMA -implementation are as follows and these are applicable to dma_map_page() as -well. - -Incorrect example 1: - dma_addr_t dma_handle; - - dma_handle = dma_map_single(dev, addr, size, direction); - if ((dma_handle & 0xffff != 0) || (dma_handle >= 0x1000000)) { - goto map_error; - } - -Incorrect example 2: - dma_addr_t dma_handle; - - dma_handle = dma_map_single(dev, addr, size, direction); - if (dma_handle == DMA_ERROR_CODE) { - goto map_error; - } +error. Doing so will ensure that the mapping code will work correctly on all +DMA implementations without any dependency on the specifics of the underlying +implementation. Using the returned address without checking for errors could +result in failures ranging from panics to silent data corruption. The same +applies to dma_map_page() as well. You should call dma_unmap_single() when the DMA activity is finished, e.g., from the interrupt which told you that the DMA transfer is done. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 4f3eecedca2d..a57875309bfd 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -546,12 +546,7 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) if (get_dma_ops(dev)->mapping_error) return get_dma_ops(dev)->mapping_error(dev, dma_addr); - -#ifdef DMA_ERROR_CODE - return dma_addr == DMA_ERROR_CODE; -#else return 0; -#endif } #ifndef HAVE_ARCH_DMA_SUPPORTED