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GET /api/1.1/patches/2219717/?format=api
{ "id": 2219717, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2219717/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260403170432.v4.5.If62b84471ef2c85e7ad250f0468867d6dba965ab@changeid/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/1.1/projects/2/?format=api", "name": "Linux PPC development", "link_name": "linuxppc-dev", "list_id": "linuxppc-dev.lists.ozlabs.org", "list_email": "linuxppc-dev@lists.ozlabs.org", "web_url": "https://github.com/linuxppc/wiki/wiki", "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git", "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/" }, "msgid": "<20260403170432.v4.5.If62b84471ef2c85e7ad250f0468867d6dba965ab@changeid>", "date": "2026-04-04T00:04:59", "name": "[v4,5/9] driver core: Replace dev->dma_ops_bypass with dev_dma_ops_bypass()", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "9986d68e52342c2778aa72ae93250330bbe18f0e", "submitter": { "id": 9763, "url": "http://patchwork.ozlabs.org/api/1.1/people/9763/?format=api", "name": "Douglas Anderson", "email": "dianders@chromium.org" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260403170432.v4.5.If62b84471ef2c85e7ad250f0468867d6dba965ab@changeid/mbox/", "series": [ { "id": 498687, "url": "http://patchwork.ozlabs.org/api/1.1/series/498687/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=498687", "date": "2026-04-04T00:04:54", "name": "driver core: Fix some race conditions", "version": 4, "mbox": "http://patchwork.ozlabs.org/series/498687/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2219717/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2219717/checks/", "tags": {}, "headers": { "Return-Path": "\n <linuxppc-dev+bounces-19295-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linuxppc-dev@lists.ozlabs.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=chromium.org header.i=@chromium.org header.a=rsa-sha256\n header.s=google header.b=oFnrg5W6;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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Wysocki\" <rafael@kernel.org>,\n\tDanilo Krummrich <dakr@kernel.org>,\n\tAlan Stern <stern@rowland.harvard.edu>", "Cc": "Saravana Kannan <saravanak@kernel.org>,\n\tChristoph Hellwig <hch@lst.de>,\n\tEric Dumazet <edumazet@google.com>,\n\tJohan Hovold <johan@kernel.org>,\n\tLeon Romanovsky <leon@kernel.org>,\n\tAlexander Lobakin <aleksander.lobakin@intel.com>,\n\tAlexey Kardashevskiy <aik@ozlabs.ru>,\n\tRobin Murphy <robin.murphy@arm.com>,\n\tDouglas Anderson <dianders@chromium.org>,\n\tchleroy@kernel.org,\n\tdriver-core@lists.linux.dev,\n\tgbatra@linux.ibm.com,\n\tiommu@lists.linux.dev,\n\tjgg@ziepe.ca,\n\tlinux-kernel@vger.kernel.org,\n\tlinuxppc-dev@lists.ozlabs.org,\n\tm.szyprowski@samsung.com,\n\tmaddy@linux.ibm.com,\n\tmpe@ellerman.id.au,\n\tnpiggin@gmail.com", "Subject": "[PATCH v4 5/9] driver core: Replace dev->dma_ops_bypass with\n dev_dma_ops_bypass()", "Date": "Fri, 3 Apr 2026 17:04:59 -0700", "Message-ID": "\n <20260403170432.v4.5.If62b84471ef2c85e7ad250f0468867d6dba965ab@changeid>", "X-Mailer": "git-send-email 2.53.0.1213.gd9a14994de-goog", "In-Reply-To": "<20260404000644.522677-1-dianders@chromium.org>", "References": "<20260404000644.522677-1-dianders@chromium.org>", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "X-Spam-Status": "No, score=-0.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,\n\tDKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,\n\tSPF_HELO_NONE,SPF_PASS autolearn=disabled version=4.0.1 OzLabs 8", "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org" }, "content": "In C, bitfields are not necessarily safe to modify from multiple\nthreads without locking. Switch \"dma_ops_bypass\" over to the \"flags\"\nfield so modifications are safe.\n\nCc: Christoph Hellwig <hch@lst.de>\nCc: Alexey Kardashevskiy <aik@ozlabs.ru>\nSigned-off-by: Douglas Anderson <dianders@chromium.org>\n---\nNot fixing any known bugs; problem is theoretical and found by code\ninspection. Change is done somewhat manually and only lightly tested\n(mostly compile-time tested).\n\nNOTE: even though previously we only took up a bit if\nCONFIG_DMA_OPS_BYPASS, in this change I reserve the bit\nunconditionally. While we could get the \"dynamic\" behavior by\nchanging the flags definition to be an \"enum\", it doesn't seem worth\nit at this point. This also allows us to move one \"#ifdef\" to an \"if\",\ngetting better compile-time testing of both sides of the \"if\".\n\nChanges in v4:\n- Use accessor functions for flags\n\nChanges in v3:\n- New\n\n arch/powerpc/kernel/dma-iommu.c | 8 ++++----\n include/linux/device.h | 15 +++++++--------\n kernel/dma/mapping.c | 4 +---\n 3 files changed, 12 insertions(+), 15 deletions(-)", "diff": "diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c\nindex 73e10bd4d56d..6d1899b38c3d 100644\n--- a/arch/powerpc/kernel/dma-iommu.c\n+++ b/arch/powerpc/kernel/dma-iommu.c\n@@ -67,7 +67,7 @@ bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg,\n }\n bool arch_dma_alloc_direct(struct device *dev)\n {\n-\tif (dev->dma_ops_bypass)\n+\tif (dev_dma_ops_bypass(dev))\n \t\treturn true;\n \n \treturn false;\n@@ -75,7 +75,7 @@ bool arch_dma_alloc_direct(struct device *dev)\n \n bool arch_dma_free_direct(struct device *dev, dma_addr_t dma_handle)\n {\n-\tif (!dev->dma_ops_bypass)\n+\tif (!dev_dma_ops_bypass(dev))\n \t\treturn false;\n \n \treturn is_direct_handle(dev, dma_handle);\n@@ -164,7 +164,7 @@ int dma_iommu_dma_supported(struct device *dev, u64 mask)\n \t\t * fixed ops will be used for RAM. This is limited by\n \t\t * bus_dma_limit which is set when RAM is pre-mapped.\n \t\t */\n-\t\tdev->dma_ops_bypass = true;\n+\t\tdev_set_dma_ops_bypass(dev);\n \t\tdev_info(dev, \"iommu: 64-bit OK but direct DMA is limited by %llx\\n\",\n \t\t\t dev->bus_dma_limit);\n \t\treturn 1;\n@@ -185,7 +185,7 @@ int dma_iommu_dma_supported(struct device *dev, u64 mask)\n \t}\n \n \tdev_dbg(dev, \"iommu: not 64-bit, using default ops\\n\");\n-\tdev->dma_ops_bypass = false;\n+\tdev_clear_dma_ops_bypass(dev);\n \treturn 1;\n }\n \ndiff --git a/include/linux/device.h b/include/linux/device.h\nindex fde0c72c3159..2ce89e3cfab9 100644\n--- a/include/linux/device.h\n+++ b/include/linux/device.h\n@@ -473,12 +473,18 @@ struct device_physical_location {\n *\t\tdoesn't rely on dma_ops structure.\n * @DEV_FLAG_DMA_SKIP_SYNC: DMA sync operations can be skipped for coherent\n *\t\tbuffers.\n+ * @DEV_FLAG_DMA_OPS_BYPASS: If set then the dma_ops are bypassed for the\n+ *\t\tstreaming DMA operations (->map_* / ->unmap_* / ->sync_*), and\n+ *\t\toptional (if the coherent mask is large enough) also for dma\n+ *\t\tallocations. This flag is managed by the dma ops instance from\n+ *\t\t->dma_supported.\n */\n enum struct_device_flags {\n \tDEV_FLAG_READY_TO_PROBE = 0,\n \tDEV_FLAG_CAN_MATCH = 1,\n \tDEV_FLAG_DMA_IOMMU = 2,\n \tDEV_FLAG_DMA_SKIP_SYNC = 3,\n+\tDEV_FLAG_DMA_OPS_BYPASS = 4,\n \n \tDEV_FLAG_COUNT\n };\n@@ -567,11 +573,6 @@ enum struct_device_flags {\n *\t\t sync_state() callback.\n * @dma_coherent: this particular device is dma coherent, even if the\n *\t\tarchitecture supports non-coherent devices.\n- * @dma_ops_bypass: If set to %true then the dma_ops are bypassed for the\n- *\t\tstreaming DMA operations (->map_* / ->unmap_* / ->sync_*),\n- *\t\tand optionall (if the coherent mask is large enough) also\n- *\t\tfor dma allocations. This flag is managed by the dma ops\n- *\t\tinstance from ->dma_supported.\n * @flags:\tDEV_FLAG_XXX flags. Use atomic bitfield operations to modify.\n *\n * At the lowest level, every device in a Linux system is represented by an\n@@ -685,9 +686,6 @@ struct device {\n defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)\n \tbool\t\t\tdma_coherent:1;\n #endif\n-#ifdef CONFIG_DMA_OPS_BYPASS\n-\tbool\t\t\tdma_ops_bypass : 1;\n-#endif\n \n \tDECLARE_BITMAP(flags, DEV_FLAG_COUNT);\n };\n@@ -718,6 +716,7 @@ __create_dev_flag_accessors(ready_to_probe, DEV_FLAG_READY_TO_PROBE);\n __create_dev_flag_accessors(can_match, DEV_FLAG_CAN_MATCH);\n __create_dev_flag_accessors(dma_iommu, DEV_FLAG_DMA_IOMMU);\n __create_dev_flag_accessors(dma_skip_sync, DEV_FLAG_DMA_SKIP_SYNC);\n+__create_dev_flag_accessors(dma_ops_bypass, DEV_FLAG_DMA_OPS_BYPASS);\n \n /**\n * struct device_link - Device link representation.\ndiff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c\nindex 76fc65d1a8a4..30bf8455730a 100644\n--- a/kernel/dma/mapping.c\n+++ b/kernel/dma/mapping.c\n@@ -126,11 +126,9 @@ static bool dma_go_direct(struct device *dev, dma_addr_t mask,\n \tif (likely(!ops))\n \t\treturn true;\n \n-#ifdef CONFIG_DMA_OPS_BYPASS\n-\tif (dev->dma_ops_bypass)\n+\tif (IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && dev_dma_ops_bypass(dev))\n \t\treturn min_not_zero(mask, dev->bus_dma_limit) >=\n \t\t\t dma_direct_get_required_mask(dev);\n-#endif\n \treturn false;\n }\n \n", "prefixes": [ "v4", "5/9" ] }