Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Fri, 6 May 2022 14:16:56 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@orcam.me.uk>
To:     Arnd Bergmann <arnd@kernel.org>
cc:     Bjorn Helgaas <helgaas@kernel.org>,
        Niklas Schnelle <schnelle@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        Richard Henderson <rth@twiddle.net>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Michal Simek <monstr@monstr.eu>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>,
        "David S. Miller" <davem@davemloft.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        "open list:ALPHA PORT" <linux-alpha@vger.kernel.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>,
        "open list:IA64 (Itanium) PLATFORM" <linux-ia64@vger.kernel.org>,
        "open list:M68K ARCHITECTURE" <linux-m68k@lists.linux-m68k.org>,
        "open list:MIPS" <linux-mips@vger.kernel.org>,
        "open list:PARISC ARCHITECTURE" <linux-parisc@vger.kernel.org>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@lists.ozlabs.org>,
        "open list:RISC-V ARCHITECTURE" <linux-riscv@lists.infradead.org>,
        "open list:SUPERH" <linux-sh@vger.kernel.org>,
        "open list:SPARC + UltraSPARC (sparc/sparc64)" 
        <sparclinux@vger.kernel.org>
Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select
 it as necessary
In-Reply-To: <CAK8P3a0EMK0gHOmb-jvtfVLb1dun72kYUMKpb11T_GgXiuR9Mw@mail.gmail.com>
Message-ID: <alpine.DEB.2.21.2205061415100.52331@angie.orcam.me.uk>
References: <CAK8P3a0sJgMSpZB_Butx2gO0hapYZy-Dm_QH-hG5rOaq_ZgsXg@mail.gmail.com> <20220505161028.GA492600@bhelgaas> <CAK8P3a3fmPExr70+fVb564hZdGAuPtYa-QxgMMe5KLpnY_sTrQ@mail.gmail.com> <alpine.DEB.2.21.2205061058540.52331@angie.orcam.me.uk>
 <CAK8P3a0NzG=3tDLCdPj2=A__2r_+xiiUTW=WJCBNp29x_A63Og@mail.gmail.com> <alpine.DEB.2.21.2205061314110.52331@angie.orcam.me.uk> <CAK8P3a0EMK0gHOmb-jvtfVLb1dun72kYUMKpb11T_GgXiuR9Mw@mail.gmail.com>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Fri, 6 May 2022, Arnd Bergmann wrote:

> >  So what happens if the instruction is given an I/O rather than memory BAR
> > as the relevant argument?  Is the address space indicator bit (bit #0)
> > simply ignored or what?
> 
> Not sure. My best guess is that it would actually work as you'd expect,
> but is deliberately left out of the architecture specification so they don't
> have to to validate the correctness.  Note that only a small number of
> PCIe cards are actually supported by IBM, and I think the firmware
> only passes devices to the OS if they are whitelisted.

 That makes sense, thanks!

  Maciej