linux-kernel - [PATCH v2 02/12] scsi: mpt3sas: Make MPI2_CONFIG_PAGE_IO_UNIT

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Date:   Sun,  6 Aug 2023 10:05:54 -0700
From:   James Seo <james@...iv.tech>
To:     Sathya Prakash <sathya.prakash@...adcom.com>,
        Sreekanth Reddy <sreekanth.reddy@...adcom.com>,
        Suganath Prabu Subramani 
        <suganath-prabu.subramani@...adcom.com>
Cc:     James Seo <james@...iv.tech>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        MPT-FusionLinux.pdl@...adcom.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 02/12] scsi: mpt3sas: Make MPI2_CONFIG_PAGE_IO_UNIT_8::Sensor[] a flexible array

This terminal 1-length variable array can be directly converted into
a C99 flexible array member.

As all users of MPI2_CONFIG_PAGE_IO_UNIT_8 (Mpi2IOUnitPage8_t) do not
use Sensor[], no further source changes are required to accommodate
its reduced sizeof():

- mpt3sas_config.c:mpt3sas_config_get_iounit_pg8() fetches a
  Mpi2IOUnitPage8_t into a caller-provided buffer, assuming
  sizeof(Mpi2IOUnitPage8_t) as the buffer size. It has one caller:

  - mpt3sas_base.c:_base_static_config_pages() passes the address of
    the Mpi2IOUnitPage8_t iounit_pg8 member of the per-adapter struct
    (struct MPT3SAS_ADAPTER *ioc) as the buffer. The assumed buffer
    size is therefore correct.

    However, the only subsequent use in mpt3sas of the thus populated
    ioc->iounit_pg8 is a little further on in the same function, and
    this use does not involve ioc->iounit_pg8.Sensor[].

    Note that iounit_pg8 occurs in the middle of the per-adapter
    struct, not at the end. The per-adapter struct is extensively
    used throughout mpt3sas even if its iounit_pg8 member isn't,
    resulting in an especially large amount of noise when comparing
    binary changes attributable to this commit.

Signed-off-by: James Seo <james@...iv.tech>
---
 drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h b/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h
index 42d820159c44..12b656bd883d 100644
--- a/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h
+++ b/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h
@@ -1200,12 +1200,9 @@ typedef struct _MPI2_IOUNIT8_SENSOR {
 #define MPI2_IOUNIT8_SENSOR_FLAGS_T0_ENABLE         (0x0001)
 
 /*
- *Host code (drivers, BIOS, utilities, etc.) should leave this define set to
- *one and check the value returned for NumSensors at runtime.
+ *Host code (drivers, BIOS, utilities, etc.) should check the value returned
+ *for NumSensors at runtime before using Sensor[].
  */
-#ifndef MPI2_IOUNITPAGE8_SENSOR_ENTRIES
-#define MPI2_IOUNITPAGE8_SENSOR_ENTRIES     (1)
-#endif
 
 typedef struct _MPI2_CONFIG_PAGE_IO_UNIT_8 {
 	MPI2_CONFIG_PAGE_HEADER Header;                 /*0x00 */
@@ -1214,8 +1211,7 @@ typedef struct _MPI2_CONFIG_PAGE_IO_UNIT_8 {
 	U8                      NumSensors;             /*0x0C */
 	U8                      PollingInterval;        /*0x0D */
 	U16                     Reserved3;              /*0x0E */
-	MPI2_IOUNIT8_SENSOR
-		Sensor[MPI2_IOUNITPAGE8_SENSOR_ENTRIES];/*0x10 */
+	MPI2_IOUNIT8_SENSOR     Sensor[];               /*0x10 */
 } MPI2_CONFIG_PAGE_IO_UNIT_8,
 	*PTR_MPI2_CONFIG_PAGE_IO_UNIT_8,
 	Mpi2IOUnitPage8_t, *pMpi2IOUnitPage8_t;
-- 
2.39.2