linux-kernel - Re: [RFC v2 30/39] scsi: add HAS

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Date:   Wed, 4 May 2022 23:34:48 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Niklas Schnelle <schnelle@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Hannes Reinecke <hare@...e.com>,
        Kashyap Desai <kashyap.desai@...adcom.com>,
        Sumit Saxena <sumit.saxena@...adcom.com>,
        Shivasharan S <shivasharan.srikanteshwara@...adcom.com>,
        Nilesh Javali <njavali@...vell.com>,
        "supporter:QLOGIC QLA2XXX FC-SCSI DRIVER" 
        <GR-QLogic-Storage-Upstream@...vell.com>,
        "open list:SCSI SUBSYSTEM" <linux-scsi@...r.kernel.org>,
        "open list:MEGARAID SCSI/SAS DRIVERS" 
        <megaraidlinux.pdl@...adcom.com>
Subject: Re: [RFC v2 30/39] scsi: add HAS_IOPORT dependencies

On Wed, May 4, 2022 at 10:42 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Fri, Apr 29, 2022 at 03:50:51PM +0200, Niklas Schnelle wrote:
> > In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
> > not being declared. We thus need to add HAS_IOPORT as dependency for
> > those drivers using them.
>
> Some of these drivers support devices using either I/O ports or MMIO.
> Adding the HAS_IOPORT dependency means MMIO devices that *could* work
> on systems without I/O ports, won't work.
>
> Even the MMIO-only devices are probably old and not of much interest.
> But if you want to disable them even though they *could* work, I think
> that's worth mentioning in the commit log.

I think this would again make more sense with the original CONFIG_LEGACY_PCI
conditional than the generic HAS_IOPORT one. I don't remember what the
objection was to that symbol.

I think the presence of inb()/outb() is a good indication that a driver is for
obsolete hardware, though of course there are important exceptions to this
that instead need to have the conditional in the code itself (8250,
vga, ipmi, ...)

       Arnd