Re: [PATCH v2] xen/arm: smmuv3: mark arm_smmu_disable_pasid __maybe_unused

[Julien Grall <julien@xxxxxxx>]

Hi Stewart,

I was about to commit this patch when I noticed the placement of the 
attribute doesn't match what we are usually doing in Xen.
On 13/12/2022 18:18, Stewart Hildebrand wrote:
> When building with clang 12 and CONFIG_ARM_SMMU_V3=y, we observe the
> following build error:
>
> drivers/passthrough/arm/smmu-v3.c:1408:20: error: unused function 
> 'arm_smmu_disable_pasid' [-Werror,-Wunused-function]
> static inline void arm_smmu_disable_pasid(struct arm_smmu_master *master) { }
>                     ^
>
> arm_smmu_disable_pasid is not currently called from anywhere in Xen, but
> it is inside a section of code guarded by CONFIG_PCI_ATS, which may be
> helpful in the future if the PASID feature is to be implemented. Add the
> attribute __maybe_unused to the function.
>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> ---
> v1->v2:
> Add __maybe_unused attribute instead of removing
> ---
>   xen/drivers/passthrough/arm/smmu-v3.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/xen/drivers/passthrough/arm/smmu-v3.c 
> b/xen/drivers/passthrough/arm/smmu-v3.c
> index 9c9f4630090e..0cdc862f96d1 100644
> --- a/xen/drivers/passthrough/arm/smmu-v3.c
> +++ b/xen/drivers/passthrough/arm/smmu-v3.c
> @@ -1376,6 +1376,7 @@ static int arm_smmu_enable_pasid(struct arm_smmu_master 
> *master)
>         return 0;
>   }
>   
> +__maybe_unused
>   static void arm_smmu_disable_pasid(struct arm_smmu_master *master)
The attribute should be placed after "void". I.e.:

static void __maybe_unused arm_smmu_disable_pasid(...)

>   {
>         struct pci_dev *pdev;
> @@ -1405,6 +1406,7 @@ static inline int arm_smmu_enable_pasid(struct 
> arm_smmu_master *master)
>         return 0;
>   }
>   
> +__maybe_unused
>   static inline void arm_smmu_disable_pasid(struct arm_smmu_master *master) { }
Same here.

>   #endif /* CONFIG_PCI_ATS */
>   
Cheers,

--
Julien Grall