>> Hi Bjorn, >> Thanks for review. >> >>> My goal is that a user should never have to specify a kernel boot >>> parameter or edit a modules.conf file, but the user did previously >>> have some way to influence whether we use pciehp or acpiphp. I know >>> we still have some issues, particularly with acpiphp, so I'm a little >>> concerned that by removing the CONFIG_HOTPLUG_PCI_ACPI=m, we might be >>> removing a way to work around those issues. >>> >>> A distro that previously used CONFIG_HOTPLUG_PCI_ACPI=m will now have >>> to use =y, so modules.conf is no longer applicable. Can you convince >>> me that the user still has a way to work around issues? I spent quite >>> a while trying to understand the pciehp/acpiphp dependencies, but it's >>> pretty tangled web. >> I will try my best to explain the relationships between pciehp and acpiphp >> as of v3.9-rc6. >> >> The pciehp driver always have priority over the acpiphp driver. >> That is, the acpiphp driver rejects binding to an ACPI PCI hotplug slot if >> a) The slot's parent is a PCIe port with native hotplug capability >> b) OSPM has taken over PCIe native hotplug control from BIOS. >> !(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL) >> The above check has no dependency on the loading order of pciehp and acpiphp >> drivers. So converting acpiphp driver to builit-in should be ok. >> >> On the other hand, I remember Yinghai has mentioned that some PCIe ports >> with native hotplug capability doesn't work as expected with the pciehp driver >> and should be managed by the acpiphp driver. Currently we could achieve that >> by using boot param "pcie_ports=compat", but this will disable PCIe port >> drivers altogether. And I also remember that Rafael has mentioned that >> some BIOSes exhibit strange dependency among PCIe OSC controls, so it's >> not feasible to only disable PCIe native hotplug. >> >> For "pciehp_force", it does only affect the way pciehp to detect a hotplug >> slot, it doesn't affect acpiphp at all. >> >> To sum up, converting acpiphp as built-in should not affect the relationship >> between pciehp and acpiphp driver. > > My concern is that a user used to be able to remove acpiphp from > modules.conf. Now removing acpiphp will require a kernel rebuild. > But maybe that won't turn out to be a problem. Hi Bjorn, If user don't want to occupy the slot by acpiphp. Conservative approach, what about add a kernel parameter to control acpiphp to enumerate slot ? Thanks! Yijing > >> So how about splitting this patch into >> two and adding more comments for the Kconfig change? > > Yes, please at least split this into two. While you're at it, please > also split the first patch into "remove unnecessary is_added guard" > and "cleanup." > > Bjorn > > . > -- Thanks! Yijing -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
