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Thu, 30 Oct 2025 07:06:50 -0700 (PDT) Received: from ho-tower-lan.lan ([185.48.77.170]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429952d5c9dsm33438674f8f.26.2025.10.30.07.06.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Oct 2025 07:06:50 -0700 (PDT) From: James Clark Date: Thu, 30 Oct 2025 14:05:27 +0000 Subject: [PATCH] dma-mapping: Allow use of DMA_BIT_MASK(64) in global scope Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251030-james-fix-dma_bit_mask-v1-1-ad1ce7cfab6e@linaro.org> X-B4-Tracking: v=1; b=H4sIAKZwA2kC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDI1NDA2MD3azE3NRi3bTMCt2U3MT4pMyS+NzE4mxdMyOTlKTUJAvLxLREJaD mgqJUoBqwwdGxtbUACyPxD2gAAAA= To: Marek Szyprowski , Robin Murphy , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Stephen Rothwell , Mark Brown , Vinod Koul , Arnd Bergmann , Guodong Xu Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, James Clark X-Mailer: b4 0.14.0 Clang doesn't like that (1ULL<<(64)) overflows when initializing a global scope variable, even if that part of the ternary isn't used when n =3D 64. The same initialization can be done without warnings in function scopes, and GCC doesn't mind either way. The build failure that highlighted this was already fixed in a different way [1], which also has detailed links to the Clang issues. However it's not going to be long before the same thing happens again, so it's better to fix the root cause. Fix it by using GENMASK_ULL() which does exactly the same thing, is much more readable anyway, and doesn't have a shift that overflows. [1]: https://lore.kernel.org/all/20250918-mmp-pdma-simplify-dma-addressing-= v1-1-5c2be2b85696@riscstar.com/ Signed-off-by: James Clark Reviewed-by: Nathan Chancellor --- include/linux/dma-mapping.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 8248ff9363ee..2ceda49c609f 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -90,7 +90,7 @@ */ #define DMA_MAPPING_ERROR (~(dma_addr_t)0) =20 -#define DMA_BIT_MASK(n) (((n) =3D=3D 64) ? ~0ULL : ((1ULL<<(n))-1)) +#define DMA_BIT_MASK(n) GENMASK_ULL(n - 1, 0) =20 struct dma_iova_state { dma_addr_t addr; --- base-commit: e53642b87a4f4b03a8d7e5f8507fc3cd0c595ea6 change-id: 20251030-james-fix-dma_bit_mask-624dbeb89afa Best regards, --=20 James Clark