Re: [PATCH v1] hwmon: (yogafan) Massive hardware expansion and structural refactoring

From: Rong Zhang

Date: Sat Apr 18 2026 - 07:29:33 EST

Hi Sergio,

On Sat, 2026-04-18 at 18:31 +0800, Rong Zhang wrote:
> Hi Sergio,
>
> On Sat, 2026-04-18 at 05:37 +0800, kernel test robot wrote:
> > Hi Sergio,
> >
> > kernel test robot noticed the following build errors:
> >
> > [auto build test ERROR on groeck-staging/hwmon-next]
> > [also build test ERROR on linus/master next-20260416]
> > [cannot apply to v7.0]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url: https://github.com/intel-lab-lkp/linux/commits/Sergio-Melas/hwmon-yogafan-Massive-hardware-expansion-and-structural-refactoring/20260417-063319
> > base: https://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging.git hwmon-next
> > patch link: https://lore.kernel.org/r/20260413060931.31091-2-sergiomelas%40gmail.com
> > patch subject: [PATCH v1] hwmon: (yogafan) Massive hardware expansion and structural refactoring
> > config: loongarch-allmodconfig (https://download.01.org/0day-ci/archive/20260418/202604180539.EuswNnjG-lkp@xxxxxxxxx/config)
> > compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260418/202604180539.EuswNnjG-lkp@xxxxxxxxx/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > Closes: https://lore.kernel.org/oe-kbuild-all/202604180539.EuswNnjG-lkp@xxxxxxxxx/
> >
> > All errors (new ones prefixed by >>):
> >
> > > > drivers/hwmon/yogafan.c:712:6: error: call to undeclared function 'wmi_has_guid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> > 712 | if (wmi_has_guid(LENOVO_WMI_OTHER_MODE_GUID) ||
> > | ^
> > 1 error generated.
>
> Hmm, that's a bit troublesome. Usually we should have been able to
> declare `depends on ACPI_WMI if ACPI_WMI' (new syntax since v7.0) or
> `depends on ACPI_WMI || !ACPI_WMI' as an optional dependency to prevent
> such an issue, but there is no static inline stubs for !ACPI_WMI...
>
> I'd suggest declaring `select ACPI_WMI if ACPI && X86' in Kconfig as
> some drm drivers do, at least for the time being.

Of course you'll still need to guard the wmi_has_guid() checks behind
`#ifdef CONFIG_ACPI_WMI'. Just forgot to mention that.

Hmm, in this way `depends on ACPI_WMI if ACPI_WMI' should also be OK...

Thanks,
Rong

>
> Thanks,
> Rong
>
> >
> >
> > vim +/wmi_has_guid +712 drivers/hwmon/yogafan.c
> >
> > 697
> > 698 static int yoga_fan_probe(struct platform_device *pdev)
> > 699 {
> > 700 const struct dmi_system_id *dmi_id;
> > 701 const struct yogafan_config *cfg;
> > 702 struct yoga_fan_data *data;
> > 703 struct hwmon_chip_info *chip_info;
> > 704 struct hwmon_channel_info *info;
> > 705 u32 *fan_config;
> > 706 acpi_status status;
> > 707 int i;
> > 708 const struct hwmon_channel_info **chip_info_array;
> > 709
> > 710 /* Check for WMI interfaces that handle fan/thermal management. */
> > 711 /* If present, we yield to the WMI driver to prevent double-reporting. */
> > > 712 if (wmi_has_guid(LENOVO_WMI_OTHER_MODE_GUID) ||
> > 713 wmi_has_guid(LENOVO_CAPABILITY_DATA_00_GUID) ||
> > 714 wmi_has_guid(LENOVO_WMI_FAN_GUID)) {
> > 715 dev_info(&pdev->dev, "Lenovo WMI management interface detected; yielding to WMI driver\n");
> > 716 return -ENODEV;
> > 717 }
> > 718
> > 719 dmi_id = dmi_first_match(yogafan_quirks);
> > 720 if (!dmi_id)
> > 721 return -ENODEV;
> > 722
> > 723 cfg = dmi_id->driver_data;
> > 724 data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> > 725 if (!data)
> > 726 return -ENOMEM;
> > 727
> > 728 /* * 1. Hardware Calibration & Inertia Scaling (Note 3):
> > 729 * Dynamic parameters (TAU and SLEW) are calibrated relative to fan diameter
> > 730 * based on the moment of inertia relationship (J ∝ d²).
> > 731 */
> > 732 data->config = cfg;
> > 733 data->device_max_rpm = cfg->r_max ?: 5000;
> > 734 data->internal_tau_ms = cfg->tau_ms ?: 1000; /* Robustness: Prevent zero-division */
> > 735
> > 736 /* Calculate Slew Rate based on time-to-max-RPM physics */
> > 737 data->internal_max_slew_rpm_s = data->device_max_rpm / (cfg->slew_time_s ?: 1);
> > 738
> > 739 /* * Log physical parameters for safety traceability (IEC 61508):
> > 740 * Provides a deterministic baseline for the RLLag filter verification.
> > 741 */
> > 742 dev_info(&pdev->dev, "Identified hardware: %s\n", dmi_id->ident);
> > 743 dev_info(&pdev->dev, "HAL Profile: [Tau: %ums, Slew: %u RPM/s, Max: %u RPM]\n",
> > 744 data->internal_tau_ms, data->internal_max_slew_rpm_s, data->device_max_rpm);
> > 745
> > 746 /* * 2. Deterministic Multi-Path Discovery:
> > 747 * We iterate through the available paths to find physical handles.
> > 748 * This loop tests variations until data->fan_count matches the
> > 749 * cfg->fan_count expected for this model profile.
> > 750 */
> > 751 for (i = 0; i < MAX_FANS && data->fan_count < cfg->fan_count; i++) {
> > 752 acpi_handle handle;
> > 753
> > 754 /* Integrity check: End of defined paths in the quirk table */
> > 755 if (!cfg->paths[i])
> > 756 break;
> > 757
> > 758 status = acpi_get_handle(NULL, cfg->paths[i], &handle);
> > 759 if (ACPI_SUCCESS(status)) {
> > 760 data->active_handles[data->fan_count] = handle;
> > 761 data->fan_count++;
> > 762 } else {
> > 763 /* Log variation failure for troubleshooting */
> > 764 dev_dbg(&pdev->dev, "Fan path variation %s not found\n", cfg->paths[i]);
> > 765 }
> > 766 }
> > 767
> > 768 /* Integrity Check: Fail probe if no fans were successfully registered */
> > 769 if (data->fan_count == 0) {
> > 770 dev_err(&pdev->dev, "Hardware identification failed: No fans found\n");
> > 771 return -ENODEV;
> > 772 }
> > 773
> > 774 /* * 3. HWMON Configuration:
> > 775 * Dynamically build the HWMON channel configuration based on the
> > 776 * number of fans actually discovered. We allocate one extra slot
> > 777 * to serve as a null terminator for the HWMON core.
> > 778 */
> > 779 fan_config = devm_kcalloc(&pdev->dev, data->fan_count + 1, sizeof(u32), GFP_KERNEL);
> > 780 if (!fan_config)
> > 781 return -ENOMEM;
> > 782
> > 783 for (i = 0; i < data->fan_count; i++)
> > 784 fan_config[i] = HWMON_F_INPUT | HWMON_F_MAX;
> > 785
> > 786 info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
> > 787 if (!info)
> > 788 return -ENOMEM;
> > 789
> > 790 info->type = hwmon_fan;
> > 791 info->config = fan_config;
> > 792
> > 793 /* 4. Wrap it in chip_info for registration */
> > 794 chip_info = devm_kzalloc(&pdev->dev, sizeof(*chip_info), GFP_KERNEL);
> > 795 if (!chip_info)
> > 796 return -ENOMEM;
> > 797
> > 798 chip_info->ops = &yoga_fan_hwmon_ops;
> > 799
> > 800 chip_info_array = devm_kcalloc(&pdev->dev, 2, sizeof(*chip_info_array), GFP_KERNEL);
> > 801 if (!chip_info_array)
> > 802 return -ENOMEM;
> > 803
> > 804 chip_info_array[0] = info;
> > 805 chip_info_array[1] = NULL; /* Null terminated */
> > 806
> > 807 chip_info->info = chip_info_array;
> > 808
> > 809 /* 5. Finalize registration with the accurate hardware description */
> > 810 return PTR_ERR_OR_ZERO(devm_hwmon_device_register_with_info(&pdev->dev,
> > 811 DRVNAME, data, chip_info, NULL));
> > 812 }
> > 813