[RESEND PATCH] iommu/intel: fix variable 'iommu' set but not used

[RESEND PATCH] iommu/intel: fix variable 'iommu' set but not used

[Qian Cai]

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 passing "drhd->iommu" directly to
for_each_active_iommu() which all subsequent self-assignments should be
ignored by a compiler anyway.

Signed-off-by: Qian Cai <cai@lca.pw>
---
 drivers/iommu/intel-iommu.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index a209199f3af6..86e1ddcb4a8e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3034,7 +3034,6 @@ static int __init iommu_prepare_static_identity_mapping(int hw)
 {
 	struct pci_dev *pdev = NULL;
 	struct dmar_drhd_unit *drhd;
-	struct intel_iommu *iommu;
 	struct device *dev;
 	int i;
 	int ret = 0;
@@ -3045,7 +3044,7 @@ static int __init iommu_prepare_static_identity_mapping(int hw)
 			return ret;
 	}
 
-	for_each_active_iommu(iommu, drhd)
+	for_each_active_iommu(drhd->iommu, drhd)
 		for_each_active_dev_scope(drhd->devices, drhd->devices_cnt, i, dev) {
 			struct acpi_device_physical_node *pn;
 			struct acpi_device *adev;
-- 
1.8.3.1

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Re: [RESEND PATCH] iommu/intel: fix variable 'iommu' set but not used

[Andrew Morton]

On Wed, 22 May 2019 16:36:26 -0400 Qian Cai <cai@lca.pw> wrote:

> 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 passing "drhd->iommu" directly to
> for_each_active_iommu() which all subsequent self-assignments should be
> ignored by a compiler anyway.
> 

Yes, assigning drhd->iommu to itself seems a bit nasty.  Maybe this is
a case for __mabe_unused (with a comment explaining why), if that fixes
the warning.  Dunno.

btw, for_each_active_dev_scope() and for_each_dev_scope() should be
dragged out and shot.  Or at least, should have those single-char
identifiers changed into something meaningful so poor sods like me have
a hope of understanding the code :(

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