linux-kernel - [PATCH v2] iommu/intel: fix variable 'iommu' set but not used

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Date:   Wed, 22 May 2019 21:33:14 -0400
From:   Qian Cai <cai@....pw>
To:     akpm@...ux-foundation.org
Cc:     jroedel@...e.de, dwmw2@...radead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH v2] iommu/intel: fix variable 'iommu' set but not used

The commit cf04eee8bf0e ("iommu/vt-d: Include ACPI devices in iommu=pt")
added for_each_active_iommu() in iommu_prepare_static_identity_mapping()
but never used the each element, i.e, "drhd->iommu".

drivers/iommu/intel-iommu.c: In function
'iommu_prepare_static_identity_mapping':
drivers/iommu/intel-iommu.c:3037:22: warning: variable 'iommu' set but
not used [-Wunused-but-set-variable]
 struct intel_iommu *iommu;

Fixed the warning by appending a compiler attribute __maybe_unused for it.

Suggested-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Qian Cai <cai@....pw>
---
 drivers/iommu/intel-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index a209199f3af6..09b8ff0d856a 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3034,7 +3034,8 @@ static int __init iommu_prepare_static_identity_mapping(int hw)
 {
 	struct pci_dev *pdev = NULL;
 	struct dmar_drhd_unit *drhd;
-	struct intel_iommu *iommu;
+	/* To avoid a -Wunused-but-set-variable warning. */
+	struct intel_iommu *iommu __maybe_unused;
 	struct device *dev;
 	int i;
 	int ret = 0;
-- 
2.20.1 (Apple Git-117)