linux-kernel - Re: [PATCH v7 5/7] io-64-nonatomic: add io{read|write}64[be]{_lo_hi|_hi

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Date:   Wed, 23 Aug 2017 00:07:57 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        linux-ntb@...glegroups.com,
        linux-crypto <linux-crypto@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Horia Geantă <horia.geanta@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v7 5/7] io-64-nonatomic: add io{read|write}64[be]{_lo_hi|_hi_lo}
 macros

On Tue, Aug 22, 2017 at 8:55 PM, Logan Gunthorpe <logang@...tatee.com> wrote:
> On 22/08/17 11:40 AM, Andy Shevchenko wrote:
>> Recomendation is kinda arguable. I doubt modern architectures make
>> difference between IO operations and MMIO.
>> Does, for example, PCI requires some special signal (message / wire)
>> handling when pio_*() accessors used vs. mmio_*() ones?

> Sort of. There is a difference between the two in x86.

Yes, the difference is in signaling. The question is if it's still in
use. Looks like yes...

> But really if it's
> not a valid recommendation someone should just go through and deprecate one
> of them or document better when one should be used over the other. In any
> case it's still really ugly to mix the two types in the same driver.

Mixing is ugly, totally agree.

-- 
With Best Regards,
Andy Shevchenko