linux-kernel - Re: [PATCH v2 3/3] platform/x86: Intel PMT Telemetry capability driver

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Message-ID: <CAHp75VcrjFUgUe6Vo8baT969cGzE4MFX6pFL1Vr5HOun=Cm0fA@mail.gmail.com>
Date:   Fri, 8 May 2020 12:57:52 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "David E. Box" <david.e.box@...ux.intel.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Shevchenko <andy@...radead.org>,
        Lee Jones <lee.jones@...aro.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v2 3/3] platform/x86: Intel PMT Telemetry capability driver

On Fri, May 8, 2020 at 5:18 AM David E. Box <david.e.box@...ux.intel.com> wrote:
>
> PMT Telemetry is a capability of the Intel Platform Monitoring Technology.
> The Telemetry capability provides access to device telemetry metrics that
> provide hardware performance data to users from continuous, memory mapped,
> read-only register spaces.
>
> Register mappings are not provided by the driver. Instead, a GUID is read
> from a header for each endpoint. The GUID identifies the device and is to
> be used with an XML, provided by the vendor, to discover the available set
> of metrics and their register mapping.  This allows firmware updates to
> modify the register space without needing to update the driver every time
> with new mappings. Firmware writes a new GUID in this case to specify the
> new mapping.  Software tools with access to the associated XML file can
> then interpret the changes.
>
> This module manages access to all PMT Telemetry endpoints on a system,
> regardless of the device exporting them. It creates a pmt_telemetry class
> to manage the list. For each endpoint, sysfs files provide GUID and size
> information as well as a pointer to the parent device the telemetry comes
> from. Software may discover the association between endpoints and devices
> by iterating through the list in sysfs, or by looking for the existence of

ABI needs documentation.

> the class folder under the device of interest.  A device node of the same
> name allows software to then map the telemetry space for direct access.

...

> +config INTEL_PMT_TELEM

TELEMETRY

...

> +obj-$(CONFIG_INTEL_PMT_TELEM)          += intel_pmt_telem.o

telemetry

(Inside the file it's fine to have telem)

...

> +       priv->dvsec = dev_get_platdata(&pdev->dev);
> +       if (!priv->dvsec) {
> +               dev_err(&pdev->dev, "Platform data not found\n");
> +               return -ENODEV;
> +       }

I don't see how is it being used?

--
With Best Regards,
Andy Shevchenko