linux-kernel - Re: how to fix acpi_pci_root_remap

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Date:   Fri, 17 Aug 2018 21:01:08 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     Tony Luck <tony.luck@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        jchandra@...adcom.com, Sinan Kaya <okaya@...eaurora.org>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: Re: how to fix acpi_pci_root_remap_iospace?

On Fri, Aug 17, 2018 at 6:20 PM Boris Brezillon
<boris.brezillon@...tlin.com> wrote:
>
> On Fri, 17 Aug 2018 15:56:23 +0000
> "Luck, Tony" <tony.luck@...el.com> wrote:
>
> > >> - Some targets don't have any support for I/O space on their PCI bus and just
> > >>    want to get things to compile by setting PCI_IOBASE to zero, this still opens
> > >>     up some of the same problems as above, but doesn't really help otherwise.
> >
> > That sounds horrible. Why would you want to have a driver that can't possibly
> > work on your platform compile cleanly? That's just asking for trouble. Sombody
> > might load that driver, and ... all the outb/outw/outl calls just corrupt low memory.
>
> Well, COMPILE_TEST is here just for that, and it's actually quite
> useful to detect potential compilation errors/warnings and make sure
> the driver is portable. So, either we decide that readsx/writesx() are
> not standard and we create a Kconfig option to reflect when an arch
> implements them so that drivers using those funcs can at least be
> compile-tested on a few archs, or we fix all archs that do not
> implement those functions.

What I meant is not specifically for compile testing, but for drivers
that are used and required on regular platforms and can be used with
either MMIO or PIO mode. serial_8250 is the typical example here,
but there are others as well.

       Arnd