On 23 April 2018 at 09:39, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > On Sunday, April 22, 2018 2:34:17 PM CEST Ard Biesheuvel wrote: >> On 22 April 2018 at 11:57, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: >> > On 22 April 2018 at 11:27, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: >> >> On Thu, Apr 19, 2018 at 6:58 PM, Ard Biesheuvel >> >> <ard.biesheuvel@xxxxxxxxxx> wrote: >> >>> When building ACPI bus drivers such as button.ko into the core kernel, >> >>> other drivers that depend on its symbols are loadable even when booting >> >>> with ACPI disabled. For instance, nouveau.ko has a link time dependency >> >>> on acpi_lid_open() on ACPI capable kernels, and calls it regardless of >> >>> whether the system booted via ACPI. >> >>> >> >>> However, when building button.ko as a module, it will refuse to load if >> >>> the system did not boot in ACPI mode, which subsequently prevents the >> >>> nouveau driver from loading as well, resulting in broken graphics. >> >>> >> >>> Given that returning an error from an initcall() is ignored for drivers >> >>> that are built into the kernel, >> >> >> >> Which makes sense, because they are present in the kernel anyway. >> >> >> >>> let's align the module case with this, >> >>> and not return an error when registering an ACPI bus driver on a system >> >>> that did not boot via ACPI. >> >> >> >> But why is loading a module that's never going to be used actually OK? >> >> >> >> Isn't this a problem with the assumptions made by the nouveau driver >> >> that need not be met depending on what configuration the kernel is run >> >> in? >> >> >> >> Honestly, it doesn't appear quite right to try to change the rest of >> >> the kernel to follow the nouveau's expectations. >> >> >> > >> > I don't disagree here, I am just unsure whether other options are any better. >> > >> > I think the alternative is to make acpi_lid_open() a non-modular >> > function of the ACPI core that invokes the button ACPI bus driver if >> > it was loaded, and always returns false otherwise. Would that work for >> > you? >> >> BTW not only nouveau invokes acpi_lid_open(), i915 does it as well. > > Clearly, the design is somewhat ad-hoc here. > > It looks like using module_acpi_driver() in button.c is a mistake given the > dependencies. The module initialization should ignore the > acpi_bus_register_driver() failure in there, but there's no reason for the > other ACPI driver modules to be affected by that. > > And if you change that, please add a comment referring to the dependencies > in question. > OK, will do. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
