linux-kernel - Re: [RFC 0/1] New PCI Switch Management Driver

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Message-ID: <CAL-B5D3g=ZWRg7Qh8_KumJkdg6F2+2a8=HCz2US7a4g2tKC0Lw@mail.gmail.com>
Date:   Mon, 19 Dec 2016 09:09:05 -0700
From:   Myron Stowe <myron.stowe@...il.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Jonathan Corbet <corbet@....net>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Stephen Bates <stephen.bates@...rosemi.com>,
        linux-pci <linux-pci@...r.kernel.org>, linux-doc@...r.kernel.org,
        linux-nvme@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 0/1] New PCI Switch Management Driver

I guess the obvious questions is: why is a driver for a PCI switch
necessary?  The core works with all compliant switches today and there
are no specifics for a particular design or such.

So I guess I'd like to hear the reasoning and justifications for why a
driver for a common device that should conform to the specifications
and not seem to need any special considerations is required or desired
here.

On Sat, Dec 17, 2016 at 10:09 AM, Logan Gunthorpe <logang@...tatee.com> wrote:
> Hi,
>
> [Appologies: this is a resend for some people. Due to a configuration
> error the original email was rejected by the mailing lists. I hope
> this one makes it!]
>
> We're looking to get some initial feedback on a new driver for
> a line of PCIe switches produced and produced and sold by Microsemi.
> The goal is to get the process moving to get this code included in
> upstream hopefully for 4.11. Facebook is currently gearing up to
> use this hardware in its Open Compute Platform and is pushing to
> have this driver in the upstream kernel.
>
> The following patch briefly describes the hardware and provides
> the first draft of driver code. Currently, the driver works and
> has been tested but is not feature complete. Thus, we are not looking
> to get it merged immediately. However we would like some early review,
> specifically on the interfaces and core concepts so that we don't
> do a lot of work down a path the community would reject. Barring any
> objections to this RFC, we will flesh out all the features
> and provide a completed patch for inclusion in the coming weeks.
>
> Work on a userspace tool, that utilizes this driver, is also being
> done at [1]. The tool is currently also a bit of a skeleton and
> will be fleshed out assuming there are no serious objections to our
> userspace interface. In the end, the tool will be released with a
> GPL license.
>
> The patch is based off of the v4.9 release.
>
> Thanks for your review,
>
> Logan
>
> [1] https://github.com/sbates130272/switchtec-user
>
> Logan Gunthorpe (1):
>   MicroSemi Switchtec management interface driver
>
>  Documentation/switchtec.txt    |  54 +++
>  MAINTAINERS                    |   9 +
>  drivers/pci/Kconfig            |   1 +
>  drivers/pci/Makefile           |   1 +
>  drivers/pci/switch/Kconfig     |  13 +
>  drivers/pci/switch/Makefile    |   1 +
>  drivers/pci/switch/switchtec.c | 824 +++++++++++++++++++++++++++++++++++++++++
>  drivers/pci/switch/switchtec.h | 119 ++++++
>  8 files changed, 1022 insertions(+)
>  create mode 100644 Documentation/switchtec.txt
>  create mode 100644 drivers/pci/switch/Kconfig
>  create mode 100644 drivers/pci/switch/Makefile
>  create mode 100644 drivers/pci/switch/switchtec.c
>  create mode 100644 drivers/pci/switch/switchtec.h
>
> --
> 2.1.4
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