|From:||Alex Chiang <email@example.com>|
|Subject:||[RFC PATCH 00/10] PCI core learns 'hotplug'|
|Date:||Wed, 28 Jan 2009 14:59:02 -0700|
|Cc:||firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com|
A while ago, Darrick Wong posted a patch for fakephp that kicked off some controversy: http://thread.gmane.org/gmane.linux.kernel/761944 The issue was that I broke the fakephp interface back in the 2.6.27 timeframe. After some discussion on the lists, Trent Piepho sent some patches, and I proposed a solution incorporating those patches. This is my first cut at making everyone happy. In summary, it: - introduces /sys/bus/pci/devices/.../remove for function level hot-remove - introduces /sys/bus/pci/devices/.../rescan to rescan the PCI hierarchy, starting at that device and descending to all children - introduces /sys/bus/pci/rescan to rescan the entire PCI hierarchy - restores the pre-2.6.27 fakephp interface for userspace compatability Some notes: - I did review Rolf Eike Beer's dummyphp patch at his request. It won't work for the same reasons that we cannot fix the existing fakephp driver -- both use the PCI hotplug API, namely pci_hp_register(), which enforces the semantic of "only one slots/ entry per physical slot", which clearly does not allow multiple entries for multi-function devices. One side note, Trent's new fakephp driver is also much smaller and cleaner, but the real reason is dummyphp uses the PCI hotplug API. I hope this reasoning is fair, but if folks disagree, I'm happy to discuss - I've been testing this patchset on my ia64 machines, which Linus has called "an insane mess of PCI bridges", and it seems to work well. I'm just starting to test on some x86 machines, and have been noticing some issues with BAR collisions, so this is definitely a work-in-progress. - Also, you might be wondering, "how does this patchset interact with existing hotplug drivers, like acpiphp or pciehp?" The answer is, "poorly". :( If you use the new PCI core removal/rescan and then try to modify the slot using acpiphp, you get an oops. My impression is that this behavior is the same as pre-2.6.27, where you could have loaded fakephp and acpiphp, removed the device with fakephp, and encountered an oops with acpiphp. 2.6.27 enforced the rule of "one hotplug driver per slot", at the cost of the fakephp breakage (which started this whole discussion). So, I'm not sure what to do about this. The way that we remove devices today, using pci_remove_bus_device() doesn't lend itself to safety very well, since it will just start removing devices from the bus without checking anything. Maybe we need some other API, or maybe we just live with the limitation of, "if you use PCI core hotplug, don't use the other hotplug drivers and vice versa". - Finally, a note to Jesse, even if this patchset is rejected, I'd recommend taking the ASPM fix, as that is just a pure bugfix. It could probably go into .29. Thanks. Comments welcome. /ac 1: http://lkml.org/lkml/2008/12/13/196 --- Alex Chiang (9): PCI: more whitespace cleanups PCI Hotplug: schedule fakephp for feature removal PCI Hotplug: rename legacy_fakephp to fakephp PCI: Introduce /sys/bus/pci/devices/.../rescan PCI: Introduce /sys/bus/pci/rescan PCI: Introduce /sys/bus/pci/devices/.../remove PCI: properly clean up ASPM link state on device remove PCI: always scan child buses PCI: don't scan existing devices Trent Piepho (1): PCI Hotplug: restore fakephp interface with complete reimplementation Documentation/ABI/testing/sysfs-bus-pci | 27 ++ Documentation/feature-removal-schedule.txt | 32 ++ drivers/pci/hotplug/fakephp.c | 438 +++++++--------------------- drivers/pci/pci-sysfs.c | 98 ++++++ drivers/pci/pcie/aspm.c | 4 drivers/pci/probe.c | 68 +++- drivers/pci/remove.c | 4 7 files changed, 303 insertions(+), 368 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to firstname.lastname@example.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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