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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/18/26 16:06, Jihong Min wrote: > > > On 5/19/26 06:37, Michal Pecio wrote: >> That's true. >> Making this possible is the whole purpose of "if IS_ENABLED" here: > > I re-checked the Kconfig cases, and I think you are right here. > > The two cases I was trying to avoid are: > > 1. the sensor driver is built as a module, or loads only after the > initramfs stage, but the PROM21 controller has already been bound by > the generic xhci-pci driver, so no auxiliary device exists for the > sensor driver to bind to; > > 2. the built-in generic xhci-pci driver rejects the PROM21 controller, but > xhci-pci-prom21 is only available as a module and is not present during > initramfs, leaving USB behind that controller unavailable at that > stage. > > Looking at your proposed Kconfig shape again, it handles both cases. > > If SENSORS_PROM21_XHCI=n, then no sensor support is requested and > USB_XHCI_PCI_PROM21 can stay disabled. In that case generic xhci-pci binds > the controller, which is fine because there is no sensor driver that > needs an > auxiliary device. > > If SENSORS_PROM21_XHCI=m or y and USB_XHCI_PCI=y, then > USB_XHCI_PCI_PROM21 follows USB_XHCI_PCI and becomes y. That means the > PROM21 > glue is available during early boot, creates the auxiliary device, and the > hwmon driver can still bind later if it is built as a module. > > If USB_XHCI_PCI=m, then xhci-pci itself is modular. In that case needing the > PROM21 glue module in initramfs is not a PROM21-specific built-in/module > split > problem; it is the normal requirement for a modular xHCI PCI setup. > > So I agree that tying the hidden glue option to whether > SENSORS_PROM21_XHCI is enabled is reasonable. > >> Currently, you have a weird situation where xhci-pci-prom21 always >> binds on x86 and xhci-pci on other platforms (with the unofficial PCIe >> card you mentioned), plus the sensor cannot work on other platforms. > > Agreed. I also agree that the X86 dependency is only a heuristic and is > not a > good restriction for a PCI ID based driver. PROM21 is mainly used on AMD x86 > desktop platforms today, but the unofficial PCIe card example shows that the > device can exist outside the normal AMD x86 chipset topology. > > I do not know whether other PROM21-related functionality is supported on > non-x86 platforms, but this driver does not need to prevent the xHCI > temperature sensor path from being built there. > >> One could further argue that neither should it care whether some hwmon >> driver exists at all, or which kernel releases it exists in :) > > Right. I think the cleanest result is: > > - generic xhci-pci handles PROM21 when no sensor support is requested; > - xhci-pci-prom21 handles PROM21 only when the sensor path is enabled; > - the hwmon driver remains the user-visible option. > > Unless Guenter or the USB maintainers object, I plan to change the next > revision in that direction and test the Kconfig combinations locally. > Ok with me if you are sure that it works. When you send a new revision, you might want to also change the error path as suggested. Thanks, Guenter