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Date:   Wed, 05 Apr 2023 22:31:33 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "H. Peter Anvin" <hpa@zytor.com>,
        "Niklas Schnelle" <schnelle@linux.ibm.com>,
        "Richard Henderson" <richard.henderson@linaro.org>,
        "Ivan Kokshaysky" <ink@jurassic.park.msu.ru>,
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        "Will Deacon" <will@kernel.org>,
        "Huacai Chen" <chenhuacai@kernel.org>,
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        "Michal Simek" <monstr@monstr.eu>,
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Subject: Re: [PATCH v4] Kconfig: introduce HAS_IOPORT option and select it as necessary
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On Wed, Apr 5, 2023, at 22:00, H. Peter Anvin wrote:
> On April 5, 2023 8:12:38 AM PDT, Niklas Schnelle <schnelle@linux.ibm.com> wrote:
>>On Thu, 2023-03-23 at 17:33 +0100, Niklas Schnelle wrote:
>>> We introduce a new HAS_IOPORT Kconfig option to indicate support for I/O
>>> Port access. In a future patch HAS_IOPORT=n will disable compilation of
>>> the I/O accessor functions inb()/outb() and friends on architectures
>>> which can not meaningfully support legacy I/O spaces such as s390.
>>> >>
>>Gentle ping. As far as I can tell this hasn't been picked to any tree
>>sp far but also hasn't seen complains so I'm wondering if I should send
>>a new version of the combined series of this patch plus the added
>>HAS_IOPORT dependencies per subsystem or wait until this is picked up.
>
> You need this on a system supporting not just ISA but also PCI.
>
> Typically on non-x86 architectures this is simply mapped into a memory window.

I'm pretty confident that the list is correct here, as the HAS_IOPORT
symbol is enabled exactly for the architectures that have a way to
map the I/O space. PCIe generally works fine without I/O space, the
only exception are drivers for devices that were around as early PCI.

      Arnd