linux-kernel - [PATCH v5 4/8] x86/resctrl: Add comments on RFTYPE flags hierarchy

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Date:   Thu, 1 Jun 2023 14:01:31 -0500
From:   Babu Moger <babu.moger@....com>
To:     <corbet@....net>, <reinette.chatre@...el.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>, <babu.moger@....com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
        <jmattson@...gle.com>, <daniel.sneddon@...ux.intel.com>,
        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bagasdotme@...il.com>,
        <eranian@...gle.com>, <christophe.leroy@...roup.eu>,
        <pawan.kumar.gupta@...ux.intel.com>, <jarkko@...nel.org>,
        <adrian.hunter@...el.com>, <quic_jiles@...cinc.com>,
        <peternewman@...gle.com>, <babu.moger@....com>
Subject: [PATCH v5 4/8] x86/resctrl: Add comments on RFTYPE flags hierarchy

resctrl uses RFTYPE flags for creating resctrl directory structure.

Definitions and directory structures are not documented. Add
comments to improve the readability and help future additions.

Signed-off-by: Babu Moger <babu.moger@....com>
---
 arch/x86/kernel/cpu/resctrl/internal.h |   45 ++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 2051179a3b91..c20cd6acb7a3 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -240,6 +240,51 @@ struct rdtgroup {
 
 /*
  * Define the file type flags for base and info directories.
+ *
+ * RESCTRL filesystem has two main components
+ *   a. info
+ *   b. base
+ *
+ * /sys/fs/resctrl/
+ *     |
+ *     --> info (directory and provides details on control
+ *     |         and monitoring resources)
+ *     |
+ *     --> base (Lists the files and information to interact with control
+ *               or monitor groups. Provides details on default control
+ *               group when filesystem is created. There is no directory
+ *               with name base)
+ *
+ *     info structure
+ *    -------------------------------------------------------------
+ *    --> RFTYPE_INFO
+ *        --> <info> directory
+ *            --> RFTYPE_TOP_INFO
+ *                Files: last_cmd_status
+ *
+ *        --> RFTYPE_MON_INFO
+ *            --> <L3_MON> directory
+ *                 Files: max_threshold_occupancy, mbm_local_bytes_config,
+ *                        mbm_total_bytes_config, mon_features, num_rmids
+ *
+ *        --> RFTYPE_CTRL_INFO
+ *            --> RFTYPE_RES_CACHE
+ *                --> <L2/L3> directory
+ *                     Files: bit_usage, cbm_mask, min_cbm_bits,
+ *                            num_closids, shareable_bits
+ *
+ *            --> RFTYPE_RES_MB
+ *                --> <MB/SMBA> directory
+ *                     Files: bandwidth_gran, delay_linear, min_bandwidth,
+ *                            num_closids
+ *
+ *     base structure
+ *     -----------------------------------------------------------
+ *     --> RFTYPE_BASE (Files common for both MON and CTRL groups)
+ *         Files: cpus, cpus_list, tasks
+ *
+ *     --> RFTYPE_CTRL_BASE (Files only for CTRL group)
+ *         Files: mode, schemata, size
  */
 #define RFTYPE_INFO			BIT(0)
 #define RFTYPE_BASE			BIT(1)