linux-kernel - Re: [RFC Patch 14/19] ACPI: Translate resource into master side address for bridge window resources

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Date:	Wed, 21 Jan 2015 01:50:30 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Len Brown <lenb@...nel.org>,
	Tony Luck <tony.luck@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [RFC Patch 14/19] ACPI: Translate resource into master side address for bridge window resources

On Thursday, January 08, 2015 10:33:01 AM Jiang Liu wrote:
> Add translation_offset into the result address for bridge window
> resources to form the master side address.
> 
> Currently acpi_dev_resource_{ext_}address_space() are only used for
> devices instead of bridges, so it won't break current users. Later
> it will be used to support PCI host bridge drivers.
> 
> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
> ---
>  drivers/acpi/resource.c |   14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
> index d3aa56674bd4..16d334a1ee25 100644
> --- a/drivers/acpi/resource.c
> +++ b/drivers/acpi/resource.c
> @@ -203,6 +203,20 @@ static bool acpi_decode_space(struct resource *res, resource_size_t *offset,
>  	res->start = addr->minimum;
>  	res->end = addr->maximum;
>  
> +	/*
> +	 * For bridges that translate addresses across the bridge,
> +	 * translation_offset is the offset that must be added to the
> +	 * address on the secondary side to obtain the address on the
> +	 * primary side. Non-bridge devices must list 0 for all Address
> +	 * Translation offset bits.
> +	 */
> +	if (base->producer_consumer == ACPI_PRODUCER) {

OK, so the assumption is that this check is never true in the current code, right?

> +		res->start += addr->translation_offset;
> +		res->end += addr->translation_offset;
> +	} else if (addr->translation_offset) {

And won't this break anything even if so?

> +		return false;
> +	}
> +
>  	switch(base->resource_type) {
>  	case ACPI_MEMORY_RANGE:
>  		acpi_dev_memresource_flags(res, len, wp);
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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