[PATCH v5 0/2] scsi: mpt3sas: add hwmon support

[Louis Sautier <sautier.louis@gmail.com>]

Expose the IOC and board temperature sensors of LSI / Broadcom / Avago
SAS HBAs that bind to mpt3sas through the hwmon interface. The data
lives in MPI IO Unit Page 7.

The same fields are exposed by Broadcom's userspace tooling through
the /dev/mpt[23]ctl ioctl path (typically root-only): IOCTemperature
and BoardTemperature in lsiutil; ROC and Controller in storcli.
With this driver, sensors(1) shows them unprivileged:

  $ sensors mpt3sas-pci-0200
  mpt3sas-pci-0200
  Adapter: PCI adapter
  IOC:          +42.0°C

v4 -> v5:
  v4: https://lore.kernel.org/r/20260613023833.3163507-1-sautier.louis@gmail.com
  * In mpt3sas_hwmon_register(), read IO Unit Page 7 and test sensor
    presence before allocating, so the no-sensor and error paths no
    longer allocate and free (Damien Le Moal).
  * Added Damien Le Moal's Reviewed-by to patch 2.

v3 -> v4:
  v3: https://lore.kernel.org/r/20260524210545.1333637-1-sautier.louis@gmail.com
  v3 (resend): https://lore.kernel.org/r/20260609164423.2829699-1-sautier.louis@gmail.com
  * Dropped the SCSI_MPT3SAS_HWMON Kconfig option as suggested by
    Damien Le Moal; the hwmon code is now built whenever CONFIG_HWMON
    is enabled. Used IS_REACHABLE() rather than IS_ENABLED() so
    SCSI_MPT3SAS=y with HWMON=m still builds, same pattern as i915/xe.
  * No line breaks after function return types; aligned multi-line
    call arguments to the opening parenthesis (Damien Le Moal).
  * Dropped unused #include <linux/kernel.h> from mpt3sas_hwmon.c.
  * Added Damien Le Moal's Reviewed-by to patch 1.

v2 -> v3:
  v2: https://lore.kernel.org/r/20260518184109.770185-1-sautier.louis@gmail.com
  * Removed stale Documentation/hwmon/mpt3sas.rst reference from
    Kconfig help text.

v1 -> v2:
  v1: https://lore.kernel.org/r/20260512214703.655633-1-sautier.louis@gmail.com
  * Dropped misleading Documentation/hwmon/mpt3sas.rst.
  * Dropped inaccurate concurrency-wait figure from Testing;
    corrected empirical data is in the on-list discussion.

Testing
-------

Build-tested all four SCSI_MPT3SAS x HWMON combinations (=y and =m
each), including the SCSI_MPT3SAS=y with HWMON=m case that requires
IS_REACHABLE().

Validated across three Broadcom SAS chip generations. None of the
cards had a board sensor present, so the testing only covers the
IOC channel:

  * LSI 9500-8i / SAS3816, SAS-3:
    - hwmon device registers as "mpt3sas" with only temp1 (IOC) exposed
    - IOC reading matches `storcli /c0 show temperature` and
      `lsiutil -p1 -a 25,2,0,0`
    - rmmod / modprobe cycle goes through the explicit
      unregister/register paths cleanly

  * LSI 9305-24i / SAS3224, SAS-3: same behaviour.

  * LSI 9211-4i / SAS2004, SAS-2: firmware reports both
    *TemperatureUnits = NOT_PRESENT, no hwmon device registered
    (graceful-skip path).

Not verified (no available hardware):
  * Path with both IOC and board sensors present.
  * Fahrenheit-units conversion.
  * Sub-zero readings (signed-cast path).

Louis Sautier (2):
  scsi: mpt3sas: add IO Unit Page 7 config accessor
  scsi: mpt3sas: add hwmon support

 drivers/scsi/mpt3sas/Makefile         |   2 +
 drivers/scsi/mpt3sas/mpt3sas_base.h   |  20 +++
 drivers/scsi/mpt3sas/mpt3sas_config.c |  36 +++++
 drivers/scsi/mpt3sas/mpt3sas_hwmon.c  | 191 ++++++++++++++++++++++++++
 drivers/scsi/mpt3sas/mpt3sas_scsih.c  |   6 +
 5 files changed, 255 insertions(+)
 create mode 100644 drivers/scsi/mpt3sas/mpt3sas_hwmon.c


base-commit: 5d6919055dec134de3c40167a490f33c74c12581
-- 
2.54.0