From: Arnd Bergmann <arnd@arndb.de>
To: ahs3@redhat.com
Subject: Re: [PATCH] arm64: CONFIG_DEVPORT should not be used when PCI is being used
Date: Sat, 9 Apr 2016 04:21:06 +0200
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Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Thursday 07 April 2016, Al Stone wrote:
> >>>  config DEVPORT
> >>>       bool
> >>> -     depends on !M68K
> >>> +     depends on !M68K && !ARM64
> >>
> >> Why not fix the real bug here, it's odd that only these two arches need
> >> this disabled, don't you agree?
> 
> Agreed.  It does seem odd.  I'm not sure I understand which bug you're thinking
> is the real one, though -- that DEVPORT should be disabled in all places that
> don't have ISA or that arm64 needs to have /dev/port work properly?  Or perhaps
> I missed something else entirely...

We've had a similar problem recently with ISA drivers crashing when no PCI
host registers itself for the first 0x1000 I/O port addresses.

I think both the request_resource() function and /dev/ioport should be
changed to interface with the dynamic registration of I/O port ranges
so they only ever allow access on ports that are mapped into virtual memory.

	Arnd