linux-kernel - Re: [PATCH v8 05/13] ACPI/PPTT: Add Processor Properties Topology Table parsing

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Message-ID: <CAJZ5v0jjPnyC0vm-Fb8y2hw1B9Uc2J5sZrtZYzt_ENT2Sini3A@mail.gmail.com>
Date:   Fri, 27 Apr 2018 13:02:00 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Sudeep Holla <Sudeep.Holla@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Will Deacon <Will.Deacon@....com>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv@...ts.infradead.org, wangxiongfeng2@...wei.com,
        vkilari@...eaurora.org, Al Stone <ahs3@...hat.com>,
        Dietmar Eggemann <Dietmar.Eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>, palmer@...ive.com,
        Len Brown <lenb@...nel.org>,
        John Garry <john.garry@...wei.com>, austinwc@...eaurora.org,
        tnowicki@...iumnetworks.com, jhugo@....qualcomm.com,
        timur@....qualcomm.com, Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH v8 05/13] ACPI/PPTT: Add Processor Properties Topology
 Table parsing

On Thu, Apr 26, 2018 at 1:31 AM, Jeremy Linton <jeremy.linton@....com> wrote:
> ACPI 6.2 adds a new table, which describes how processing units
> are related to each other in tree like fashion. Caches are
> also sprinkled throughout the tree and describe the properties
> of the caches in relation to other caches and processing units.
>
> Add the code to parse the cache hierarchy and report the total
> number of levels of cache for a given core using
> acpi_find_last_cache_level() as well as fill out the individual
> cores cache information with cache_setup_acpi() once the
> cpu_cacheinfo structure has been populated by the arch specific
> code.
>
> An additional patch later in the set adds the ability to report
> peers in the topology using find_acpi_cpu_topology()
> to report a unique ID for each processing unit at a given level
> in the tree. These unique id's can then be used to match related
> processing units which exist as threads, within a given
> package, etc.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> Acked-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/acpi/pptt.c | 518 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 518 insertions(+)
>  create mode 100644 drivers/acpi/pptt.c
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> new file mode 100644
> index 000000000000..cced71ef851a
> --- /dev/null
> +++ b/drivers/acpi/pptt.c
> @@ -0,0 +1,518 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * pptt.c - parsing of Processor Properties Topology Table
> + *
> + * Copyright (C) 2018, ARM
> + *
> + * This file implements parsing of Processor Properties Topology Table (PPTT)
> + * which is optionally used to describe the processor and cache topology.
> + * Due to the relative pointers used throughout the table, this doesn't
> + * leverage the existing subtable parsing in the kernel.
> + *
> + * The PPTT structure is an inverted tree, with each node potentially
> + * holding one or two inverted tree data structures describing
> + * the caches available at that level. Each cache structure optionally
> + * contains properties describing the cache at a given level which can be
> + * used to override hardware probed values.
> + */
> +#define pr_fmt(fmt) "ACPI PPTT: " fmt
> +
> +#include <linux/acpi.h>
> +#include <linux/cacheinfo.h>
> +#include <acpi/processor.h>
> +
> +/**
> + * fetch_pptt_subtable() - Find/Verify that the PPTT ref is a valid subtable

The parens above are at least redundant (if not harmful).  Everywhere
else in a similar context too.

Also kerneldoc comments document function arguments too as a rule, so
please do that here and wherever you use kerneldoc comments in the
patchset.

> + *
> + * Given the PPTT table, find and verify that the subtable entry
> + * is located within the table
> + *
> + * Return: acpi_subtable_header* or NULL
> + */
> +static struct acpi_subtable_header *fetch_pptt_subtable(struct acpi_table_header *table_hdr,
> +                                                       u32 pptt_ref)
> +{
> +       struct acpi_subtable_header *entry;
> +
> +       /* there isn't a subtable at reference 0 */
> +       if (pptt_ref < sizeof(struct acpi_subtable_header))
> +               return NULL;
> +
> +       if (pptt_ref + sizeof(struct acpi_subtable_header) > table_hdr->length)
> +               return NULL;
> +
> +       entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr, pptt_ref);
> +
> +       if (entry->length == 0)
> +               return NULL;
> +
> +       if (pptt_ref + entry->length > table_hdr->length)
> +               return NULL;
> +
> +       return entry;
> +}

Apart from the above I'm not entirely sure why you need the changes in
patch [09/13] to go in a separate patch.  All of them are new code
going into the file created by this patch, so why not to put them
here?