On Fri, Feb 21, 2014 at 12:13:13AM +0000, Matthew Garrett wrote: > On Thu, 2014-02-20 at 17:59 -0600, Russ Anderson wrote: > > On Thu, Feb 20, 2014 at 11:09:42PM +0000, Matthew Garrett wrote: > > > On Thu, 2014-02-20 at 16:45 -0600, Russ Anderson wrote: > > > > > > > > The ACPI spec requires IPMI functionality before a module loads at > > > > boot time? And the kernel is *broken* if it does not support ACIP IPMI > > > > functionality before module load time? Really? > > > > > > There's no mechanism to ensure that IPMI support will be loaded before > > > ACPI calls attempt to access IPMI operation regions. Really. > > > > And no mechanism can be added to ensure that ACPI call are > > not attempted before IPMI is initialized? A flag or lock > > or exported symbol indicating IPMI support is ready. > > ACPI functions are a black box to drivers. You make an ACPI call, the > AML code does something. We could block there, but what's the driver > supposed to do at that point? The core could call out to a module > loader, but if the driver is built in and IPMI isn't then you'll end up > with a 60 second pause in boot and a driver that doesn't work. When you say "if the driver is built in" which driver are you talking about? I thought the issue was making sure ipmi_si driver was loaded before power meter driver. > > > > > ACPI 4.0 includes support for IPMI operation regions. Modular IPMI means > > > > > that the kernel will spend a significant amount of time (potentially > > > > > until a user manually loads a driver) failing to implement part of the > > > > > IPMI specification. That's a problem, and the correct fix is to ensure > > > > > that the kernel always implements IPMI support. > > > > > > > > The ACPI spec says ipmi_si cannot be a driver? Really? > > > > What is the real problem you are trying to solve? > > > > > > The most straightforward case is that of an ACPI power meter. > > > > So it is just a matter of making sure ipmi_si modules loads before > > the ACPI power meter module loads, right? module dependency issue. > > No, because the power meter driver has no way of knowing that a vendor > has implemented this interface via IPMI. *Any* ACPI entry point could > theoretically reference IPMI code, even the _INI method that's called > during ACPI core init. If it does, and if you don't have built-in ACPI > support, you'd fail ACPI initialisation and things would go downhill > from there. Again, it sounds like as long as ipmi_si driver is loaded before power meter driver, power meter driver is fine. -- Russ Anderson, Kernel and Performance Software Team Manager SGI - Silicon Graphics Inc rja@xxxxxxx -- 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
