linux-kernel - [PATCH AUTOSEL 5.15 3/7] dma-mapping: avoid potential unused data compilation warning

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Message-Id: <20250429235339.538269-3-sashal@kernel.org>
Date: Tue, 29 Apr 2025 19:53:34 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	iommu@...ts.linux.dev
Subject: [PATCH AUTOSEL 5.15 3/7] dma-mapping: avoid potential unused data compilation warning

From: Marek Szyprowski <m.szyprowski@...sung.com>

[ Upstream commit c9b19ea63036fc537a69265acea1b18dabd1cbd3 ]

When CONFIG_NEED_DMA_MAP_STATE is not defined, dma-mapping clients might
report unused data compilation warnings for dma_unmap_*() calls
arguments. Redefine macros for those calls to let compiler to notice that
it is okay when the provided arguments are not used.

Reported-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
Tested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Link: https://lore.kernel.org/r/20250415075659.428549-1-m.szyprowski@samsung.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/dma-mapping.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index fe3849434b2a2..d7b91f82b0dce 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -595,10 +595,14 @@ static inline int dma_mmap_wc(struct device *dev,
 #else
 #define DEFINE_DMA_UNMAP_ADDR(ADDR_NAME)
 #define DEFINE_DMA_UNMAP_LEN(LEN_NAME)
-#define dma_unmap_addr(PTR, ADDR_NAME)           (0)
-#define dma_unmap_addr_set(PTR, ADDR_NAME, VAL)  do { } while (0)
-#define dma_unmap_len(PTR, LEN_NAME)             (0)
-#define dma_unmap_len_set(PTR, LEN_NAME, VAL)    do { } while (0)
+#define dma_unmap_addr(PTR, ADDR_NAME)           \
+	({ typeof(PTR) __p __maybe_unused = PTR; 0; })
+#define dma_unmap_addr_set(PTR, ADDR_NAME, VAL)  \
+	do { typeof(PTR) __p __maybe_unused = PTR; } while (0)
+#define dma_unmap_len(PTR, LEN_NAME)             \
+	({ typeof(PTR) __p __maybe_unused = PTR; 0; })
+#define dma_unmap_len_set(PTR, LEN_NAME, VAL)    \
+	do { typeof(PTR) __p __maybe_unused = PTR; } while (0)
 #endif
 
 #endif /* _LINUX_DMA_MAPPING_H */
-- 
2.39.5