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Date:   Wed, 28 Feb 2018 22:28:53 -0500 (EST)
Message-Id: <20180228.222853.1570972177848923005.davem@davemloft.net>
To:     helgaas@kernel.org
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        bhelgaas@google.com, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org
Subject: Re: [PATCH] sparc: Use generic pci_mmap_resource_range()
From:   David Miller <davem@davemloft.net>
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From: Bjorn Helgaas <helgaas@kernel.org>
Date: Wed, 28 Feb 2018 17:08:29 -0600

> On Mon, Feb 19, 2018 at 10:30:25AM -0500, David Miller wrote:
>> From: David Woodhouse <dwmw2@infradead.org>
>> Date: Mon, 19 Feb 2018 15:24:18 +0000
>> 
>> >> For one, the sparc specific code allows mmap'ing any address range
>> >> within a PCI bus device.??The generic code does not allow that.
>> > 
>> > 
>> > You mean any address range in a given PCI bus even if there is no
>> > actual device with a BAR at the corresponding address?
>> > 
>> > Would I be right to assume this was only available through the legacy
>> > procfs API? I think it should be possible to accommodate it, and it
>> > does look like I'd missed this requirement the first time round; thanks
>> > for pointing it out.
>> 
>> It was probably the case that only procfs could do it.
>> 
>> It is the mechanism by which we were able to let the X server poke
>> around in VGA ISA space.  It does a bus I/O space map for the bus
>> device above the VGA card.
> 
> What's the bottom line?  Do we want this for sparc?  If so, do you
> want to take it, Dave M, or would you like me to?

The bottom line is that David W.'s patch would break sparc so
we don't want this.