linux-kernel - Re: [PATCH] PCI: make pci

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Message-ID: <20190130165332.GG229773@google.com>
Date:   Wed, 30 Jan 2019 10:53:32 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     changbin.du@...il.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: make pci_size() return real size

On Sat, Oct 13, 2018 at 08:49:19AM +0800, changbin.du@...il.com wrote:
> From: Du Changbin <changbin.du@...il.com>
> 
> Currently, the pci_size() function actually return 'size-1'.
> Make it return real size to avoid confusing.
> 
> Signed-off-by: Du Changbin <changbin.du@...il.com>

Applied to pci/enumeration for v5.1, thanks!

I think it's good to have the "end = start + size - 1" idiom made more
obvious to help avoid off-by-one errors.

> ---
>  drivers/pci/probe.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 201f9e5ff55c..8ff2b1413865 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -121,13 +121,13 @@ static u64 pci_size(u64 base, u64 maxbase, u64 mask)
>  	 * Get the lowest of them to find the decode size, and from that
>  	 * the extent.
>  	 */
> -	size = (size & ~(size-1)) - 1;
> +	size = size & ~(size-1);
>  
>  	/*
>  	 * base == maxbase can be valid only if the BAR has already been
>  	 * programmed with all 1s.
>  	 */
> -	if (base == maxbase && ((base | size) & mask) != mask)
> +	if (base == maxbase && ((base | (size - 1)) & mask) != mask)
>  		return 0;
>  
>  	return size;
> @@ -278,7 +278,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
>  			/* Above 32-bit boundary; try to reallocate */
>  			res->flags |= IORESOURCE_UNSET;
>  			res->start = 0;
> -			res->end = sz64;
> +			res->end = sz64 - 1;
>  			pci_info(dev, "reg 0x%x: can't handle BAR above 4GB (bus address %#010llx)\n",
>  				 pos, (unsigned long long)l64);
>  			goto out;
> @@ -286,7 +286,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
>  	}
>  
>  	region.start = l64;
> -	region.end = l64 + sz64;
> +	region.end = l64 + sz64 - 1;
>  
>  	pcibios_bus_to_resource(dev->bus, res, &region);
>  	pcibios_resource_to_bus(dev->bus, &inverted_region, res);
> -- 
> 2.17.1
>