linux-kernel - RE: [patch v1] x86/platform/mellanox: introduce support for Mellanox systems platform

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Date:   Mon, 12 Sep 2016 07:48:24 +0000
From:   Vadim Pasternak <vadimp@...lanox.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "linux@...ck-us.net" <linux@...ck-us.net>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>
Subject: RE: [patch v1] x86/platform/mellanox: introduce support for Mellanox
 systems platform



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Monday, September 12, 2016 10:41 AM
> To: Vadim Pasternak <vadimp@...lanox.com>
> Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> davem@...emloft.net; geert@...ux-m68k.org; akpm@...ux-foundation.org;
> kvalo@...eaurora.org; mchehab@...nel.org; linux@...ck-us.net;
> x86@...nel.org; linux-kernel@...r.kernel.org; platform-driver-
> x86@...r.kernel.org; jiri@...nulli.us
> Subject: Re: [patch v1] x86/platform/mellanox: introduce support for Mellanox
> systems platform
> 
> On Mon, Sep 12, 2016 at 07:23:59AM +0000, Vadim Pasternak wrote:
> >
> >
> > > -----Original Message-----
> > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > Sent: Monday, September 12, 2016 10:05 AM
> > > To: Vadim Pasternak <vadimp@...lanox.com>
> > > Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> > > davem@...emloft.net; geert@...ux-m68k.org;
> > > akpm@...ux-foundation.org; kvalo@...eaurora.org; mchehab@...nel.org;
> > > linux@...ck-us.net; x86@...nel.org; linux-kernel@...r.kernel.org;
> > > platform-driver- x86@...r.kernel.org; jiri@...nulli.us
> > > Subject: Re: [patch v1] x86/platform/mellanox: introduce support for
> > > Mellanox systems platform
> > >
> > > On Mon, Sep 12, 2016 at 06:44:03AM +0000, Vadim Pasternak wrote:
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > > > Sent: Monday, September 12, 2016 9:13 AM
> > > > > To: Vadim Pasternak <vadimp@...lanox.com>
> > > > > Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> > > > > davem@...emloft.net; geert@...ux-m68k.org;
> > > > > akpm@...ux-foundation.org; kvalo@...eaurora.org;
> > > > > mchehab@...nel.org; linux@...ck-us.net; x86@...nel.org;
> > > > > linux-kernel@...r.kernel.org;
> > > > > platform-driver- x86@...r.kernel.org; jiri@...nulli.us
> > > > > Subject: Re: [patch v1] x86/platform/mellanox: introduce support
> > > > > for Mellanox systems platform
> > > > >
> > > > > On Mon, Sep 12, 2016 at 06:29:58AM +0000, vadimp@...lanox.com
> wrote:
> > > > > > From: Vadim Pasternak <vadimp@...lanox.com>
> > > > > >
> > > > > > Enable system support for the Mellanox Technologies platform,
> > > > > > which provides support for the next Mellanox basic systems:
> > > > > > "msx6710", "msx6720", "msb7700", "msn2700", "msx1410",
> > > > > > "msn2410", "msb7800", "msn2740", "msn2100" and also various
> > > > > > number of derivative systems from the above basic types.
> > > > >
> > > > > What does "system support" mean?
> > > > >
> > > > > Why can't this just be a "normal" PCI driver, as you are just
> > > > > accessing a PCI device and doing something with it, seems odd to
> > > > > claim it is a
> > > "platform" driver.
> > > > >
> > > >
> > > > This driver also activates probes to create i2c platform driver and muxes.
> > >
> > > And how does it do that?  Through the PCI device?
> > >
> > > > For ARM and PPC based systems I can activate such stuff through dts.
> > > > To be honest I don't know what is the right way to do such things
> > > > for
> > > > x86 systems.
> > >
> > > How is it found in a x86 system, in ACPI?
> > >
> >
> > We have no support in ACPI.
> > Currently it could be found through DMI.
> >
> > > > If I will move PCI related stuff to separate driver, could you
> > > > suggest some right location for that?
> > >
> > > Depends on what it does.
> >
> > It creates platform i2c driver (Mellanox controller), like:
> > platform_device_register_simple("i2c_mlxcpld", -1,
> >                                                          NULL, 0); And
> > two mux platform device instances, like:
> > platform_device_register_resndata(dev,
> >                                                 " i2c-mux-reg", i, NULL,
> >                                                 0, &mlxplat_mux_data[i],
> >
> > sizeof(mlxplat_mux_data[i]));
> 
> Ugh.  Really?  These aren't on a real bus?  What is this, the 1990's?

Actually this is 2015-2016.
Many switches use i2c virtual buses infrastructure for placing slow devices for system monitoring and control.

> 
> Ok, a DMI driver for these makes sense in the platform directory to me, but you
> have to convince the maintainer of this subsystem :)
> 
> And rip all of that PCI stuff out, that belongs in a PCI driver.
> 
Thank you very much for all your inputs.

> thanks,
> 
> greg k-h

Thanks,

Vadim.