linux-kernel - Re: [PATCH 1/1] iommu/dma: fix trival coding style mistake

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Date:   Wed, 23 May 2018 13:51:56 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Zhen Lei <thunder.leizhen@...wei.com>,
        Joerg Roedel <joro@...tes.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] iommu/dma: fix trival coding style mistake

On 23/05/18 07:02, Zhen Lei wrote:
> No functional changes.

What's the mistake?

> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>   drivers/iommu/dma-iommu.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index ddcbbdb..4e885f7 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -231,6 +231,9 @@ static int iova_reserve_iommu_regions(struct device *dev,
>   	LIST_HEAD(resv_regions);
>   	int ret = 0;
> 
> +	if (!dev)
> +		return 0;

Logically, it makes no sense at all to call this function without a 
valid device; doing the check in init_domain was a deliberate decision 
to reflect that. This isn't a cleanup path shared by multiple callers 
where the "accept NULL for simplicity" argument might apply.

> +
>   	if (dev_is_pci(dev))
>   		iova_reserve_pci_windows(to_pci_dev(dev), iovad);
> 
> @@ -246,11 +249,12 @@ static int iova_reserve_iommu_regions(struct device *dev,
>   		hi = iova_pfn(iovad, region->start + region->length - 1);
>   		reserve_iova(iovad, lo, hi);
> 
> -		if (region->type == IOMMU_RESV_MSI)
> +		if (region->type == IOMMU_RESV_MSI) {
>   			ret = cookie_init_hw_msi_region(cookie, region->start,
>   					region->start + region->length);
> -		if (ret)
> -			break;
> +			if (ret)
> +				break;
> +		}

Why? ret is already initialised appropriately, and the coding style even 
says that going beyond 3 levels of indentation is undesirable...

Robin.

>   	}
>   	iommu_put_resv_regions(dev, &resv_regions);
> 
> @@ -308,8 +312,6 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>   	}
> 
>   	init_iova_domain(iovad, 1UL << order, base_pfn);
> -	if (!dev)
> -		return 0;
> 
>   	return iova_reserve_iommu_regions(dev, domain);
>   }
> --
> 1.8.3
> 
> 
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 

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