linux-kernel - Re: [PATCH -next] iommu/arm-smmu-v3: Fix build error without CONFIG_PCI

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Date:   Tue, 3 Sep 2019 07:30:29 +0100
From:   Will Deacon <will@...nel.org>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     robin.murphy@....com, joro@...tes.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] iommu/arm-smmu-v3: Fix build error without
 CONFIG_PCI_ATS

On Tue, Sep 03, 2019 at 10:42:12AM +0800, YueHaibing wrote:
> If CONFIG_PCI_ATS is not set, building fails:
> 
> drivers/iommu/arm-smmu-v3.c: In function arm_smmu_ats_supported:
> drivers/iommu/arm-smmu-v3.c:2325:35: error: struct pci_dev has no member named ats_cap; did you mean msi_cap?
>   return !pdev->untrusted && pdev->ats_cap;
>                                    ^~~~~~~
> 
> ats_cap should only used when CONFIG_PCI_ATS is defined,
> so use #ifdef block to guard this.
> 
> Fixes: bfff88ec1afe ("iommu/arm-smmu-v3: Rework enabling/disabling of ATS for PCI masters")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/iommu/arm-smmu-v3.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 66bf641..44ac9ac 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2313,7 +2313,7 @@ static void arm_smmu_install_ste_for_dev(struct arm_smmu_master *master)
>  
>  static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
>  {
> -	struct pci_dev *pdev;
> +	struct pci_dev *pdev __maybe_unused;
>  	struct arm_smmu_device *smmu = master->smmu;
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(master->dev);
>  
> @@ -2321,8 +2321,10 @@ static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
>  	    !(fwspec->flags & IOMMU_FWSPEC_PCI_RC_ATS) || pci_ats_disabled())
>  		return false;
>  
> +#ifdef CONFIG_PCI_ATS
>  	pdev = to_pci_dev(master->dev);
>  	return !pdev->untrusted && pdev->ats_cap;
> +#endif
>  }

Hmm, I really don't like the missing return statement here, even though we
never get this far thanks to the feature not getting set during ->probe().
I'd actually prefer just to duplicate the function:

#ifndef CONFIG_PCI_ATS
static bool
arm_smmu_ats_supported(struct arm_smmu_master *master) { return false; }
#else
<current code here>
#endif

Can you send a v2 like that, please?

Will