linux-kernel - Re: [PATCH 2/4] x86/amd_nb: add support for newer PCI topologies

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Date:   Wed, 7 Nov 2018 05:51:22 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Borislav Petkov <bp@...en8.de>, Bjorn Helgaas <helgaas@...nel.org>
Cc:     "Woods, Brian" <Brian.Woods@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Clemens Ladisch <clemens@...isch.de>,
        Jean Delvare <jdelvare@...e.com>, Pu Wen <puwen@...on.cn>,
        Jia Zhang <qianyue.zj@...baba-inc.com>,
        Takashi Iwai <tiwai@...e.de>,
        Andy Whitcroft <apw@...onical.com>,
        Colin Ian King <colin.king@...onical.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        Sumeet Pawnikar <sumeet.r.pawnikar@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 2/4] x86/amd_nb: add support for newer PCI topologies

On 11/7/18 1:18 AM, Borislav Petkov wrote:
> On Tue, Nov 06, 2018 at 05:20:41PM -0600, Bjorn Helgaas wrote:
>> Or maybe even drivers/acpi/thermal.c, which claims every Thermal Zone
>> (ACPI 6.2, sec 11), would be sufficient.  I don't know what the
>> relationship between hwmon and other thermal stuff, e.g.,
>> Documentation/thermal/sysfs-api.txt is.  acpi/thermal.c looks tied
>> into the drivers/thermal stuff (it registers "thermal_zone" devices),
>> but not to hwmon.
> 
> Err, I still don't think I'm catching your drift but let me stop you
> right there: amd_nb is not there only for hwmon/k10temp. It is a small
> interface glue if you will, which exports the CPU functionality in PCI
> config space to other consumers.
> 

Also, thermal and hwmon are orthogonal, just like hwmon and iio. One would
typically have a driver in one subsystem, in some cases bridging to the
other subsystem, but one would not have drivers in both subsystems.
I think Bjorn is suggesting that the k10temp driver should move to the
thermal subsystem, though I don't really understand what that has to do
with finding the correct PCI device(s) to query. Or maybe I misunderstand.

Guenter

> So it is not really a driver - it is used by drivers to talk/query CPU
> settings through it.
> 
> With that said, I don't think I understand all that talk about PNP IDs
> and ACPI methods. But maybe I'm missing something...
> 
> So what's up?
>