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

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Date:   Tue, 6 Nov 2018 23:00:59 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     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>,
        Guenter Roeck <linux@...ck-us.net>, 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>,
        "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 Tue, Nov 06, 2018 at 03:42:56PM -0600, Bjorn Helgaas wrote:
> This isn't some complicated new device where the programming model
> changed on the new CPU.  This is a thermometer that was already
> supported.  ACPI provides plenty of functionality that could be used
> to support this generically, e.g., see drivers/acpi/thermal.c,
> drivers/thermal/int340x_thermal/processor_thermal_device.c, etc.

Ok, you say ACPI but how do you envision practically doing that? I mean,
this is used by old boxes too - ever since K8. So how do we go and add
ACPI functionality to old boxes?

Or do you mean it should simply be converted to do pci_register_driver()
with a struct pci_driver pointer which has all those PCI device IDs in a
table? I'm looking at the last example
drivers/thermal/int340x_thermal/processor_thermal_device.c you gave above.

> But maybe there's some real value in the nitty-gritty device-specific
> code in amd_nb.c.  If so, I guess you're stuck with updates like this
> and negotiating with the distros to do backports and new releases.

Well, even if it is converted to a different registration scheme, you
still need to add new PCI device IDs to the table, no? So *some* sort of
enablement still needs to happen.

And then the argument about needing enablement for distros is moot
because it still needs enablement/backporting - regardless of the
registration scheme.

Or do you mean something else?

I mean, don't get me wrong, I don't mind if it gets converted to
pci_register_driver() if you think it fits better this way with the
drivers registering with PCI devices - I'm just trying to understand the
reasoning for it.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.