kernel/linux.git/drivers/pci/hotplug/ibmphp_ebda.c, branch v4.19.77

PCI: hotplug: Demidlayer registration with the core

2018-07-23T22:04:13+00:00

When a hotplug driver calls pci_hp_register(), all steps necessary for registration are carried out in one go, including creation of a kobject and addition to sysfs. That's a problem for pciehp once it's converted to enable/disable the slot exclusively from the IRQ thread: The thread needs to be spawned after creation of the kobject (because it uses the kobject's name), but before addition to sysfs (because it will handle enable/disable requests submitted via sysfs). pci_hp_deregister() does offer a ->release callback that's invoked after deletion from sysfs and before destruction of the kobject. But because pci_hp_register() doesn't offer a counterpart, hotplug drivers' ->probe and ->remove code becomes asymmetric, which is error prone as recently discovered use-after-free bugs in pciehp's ->remove hook have shown. In a sense, this appears to be a case of the midlayer antipattern: "The core thesis of the "midlayer mistake" is that midlayers are bad and should not exist. That common functionality which it is so tempting to put in a midlayer should instead be provided as library routines which can [be] used, augmented, or ignored by each bottom level driver independently. Thus every subsystem that supports multiple implementations (or drivers) should provide a very thin top layer which calls directly into the bottom layer drivers, and a rich library of support code that eases the implementation of those drivers. This library is available to, but not forced upon, those drivers." -- Neil Brown (2009), https://lwn.net/Articles/336262/ The presence of midlayer traits in the PCI hotplug core might be ascribed to its age: When it was introduced in February 2002, the blessings of a library approach might not have been well known: https://git.kernel.org/tglx/history/c/a8a2069f432c For comparison, the driver core does offer split functions for creating a kobject (device_initialize()) and addition to sysfs (device_add()) as an alternative to carrying out everything at once (device_register()). This was introduced in October 2002: https://git.kernel.org/tglx/history/c/8b290eb19962 The odd ->release callback in the PCI hotplug core was added in 2003: https://git.kernel.org/tglx/history/c/69f8d663b595 Clearly, a library approach would not force every hotplug driver to implement a ->release callback, but rather allow the driver to remove the sysfs files, release its data structures and finally destroy the kobject. Alternatively, a driver may choose to remove everything with pci_hp_deregister(), then release its data structures. To this end, offer drivers pci_hp_initialize() and pci_hp_add() as a split-up version of pci_hp_register(). Likewise, offer pci_hp_del() and pci_hp_destroy() as a split-up version of pci_hp_deregister(). Eliminate the ->release callback and move its code into each driver's teardown routine. Declare pci_hp_deregister() void, in keeping with the usual kernel pattern that enablement can fail, but disablement cannot. It only returned an error if the caller passed in a NULL pointer or a slot which has never or is no longer registered or is sharing its name with another slot. Those would be bugs, so WARN about them. Few hotplug drivers actually checked the return value and those that did only printed a useless error message to dmesg. Remove that. For most drivers the conversion was straightforward since it doesn't matter whether the code in the ->release callback is executed before or after destruction of the kobject. But in the case of ibmphp, it was unclear to me whether setting slot_cur->ctrl and slot_cur->bus_on to NULL needs to happen before the kobject is destroyed, so I erred on the side of caution and ensured that the order stays the same. Another nontrivial case is pnv_php, I've found the list and kref logic difficult to understand, however my impression was that it is safe to delete the list element and drop the references until after the kobject is destroyed. Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Acked-by: Andy Shevchenko # drivers/platform/x86 Cc: Rafael J. Wysocki Cc: Len Brown Cc: Scott Murray Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Gavin Shan Cc: Sebastian Ott Cc: Gerald Schaefer Cc: Corentin Chary Cc: Darren Hart Cc: Andy Shevchenko

PCI: Add SPDX GPL-2.0+ to replace GPL v2 or later boilerplate

2018-01-28T21:49:06+00:00

Add SPDX GPL-2.0+ to all PCI files that specified the GPL and allowed either GPL version 2 or any later version. Remove the boilerplate GPL version 2 or later language, relying on the assertion in b24413180f56 ("License cleanup: add SPDX GPL-2.0 license identifier to files with no license") that the SPDX identifier may be used instead of the full boilerplate text. Signed-off-by: Bjorn Helgaas Reviewed-by: Greg Kroah-Hartman

PCI: Constify hotplug pci_device_id structures

2017-08-10T20:21:42+00:00

pci_device_id are not supposed to change at runtime. All functions working with pci_device_id provided by work with const pci_device_id. So mark the non-const structs as const. Signed-off-by: Arvind Yadav [bhelgaas: squash shpchp, ibmphp, bmphp_ebda, cpcihp_zt5550, cpqphp] Signed-off-by: Bjorn Helgaas

Merge branch 'pci/trivial' into next

2016-01-20T17:48:25+00:00

* pci/trivial: PCI: shpchp: Constify hpc_ops structure PCI: Use kobj_to_dev() instead of open-coding it PCI: Use to_pci_dev() instead of open-coding it PCI: Fix all whitespace issues PCI/MSI: Fix typos in

PCI: hotplug: Use list_for_each_entry() to simplify code

2016-01-10T22:10:29+00:00

Use list_for_each_entry() instead of list_for_each() to simplify the code. Signed-off-by: Geliang Tang Signed-off-by: Bjorn Helgaas

PCI: Fix all whitespace issues

2016-01-08T16:35:24+00:00

Fix all whitespace issues (missing or needed whitespace) in all files in drivers/pci. Code is compiled with allyesconfig before and after code changes and objects are recorded and checked with objdiff and they are not changed after this commit. Signed-off-by: Bogicevic Sasa Signed-off-by: Bjorn Helgaas

PCI: Remove unnecessary curly braces

2014-09-24T13:49:20+00:00

Remove curly braces in simple "if" cases. No functional change. Signed-off-by: Quentin Lambert Signed-off-by: Bjorn Helgaas

PCI: Whitespace cleanup

2014-06-11T02:20:19+00:00

Fix various whitespace errors. No functional change. [bhelgaas: fix other similar problems] Signed-off-by: Ryan Desfosses Signed-off-by: Bjorn Helgaas

PCI: Fix whitespace, capitalization, and spelling errors

2013-11-14T18:28:18+00:00

Fix whitespace, capitalization, and spelling errors. No functional change. I know "busses" is not an error, but "buses" was more common, so I used it consistently. Signed-off-by: Marta Rybczynska (pci_reset_bridge_secondary_bus()) Signed-off-by: Bjorn Helgaas Acked-by: Rafael J. Wysocki

pci: hotplug: Fix typo in pci

2012-07-24T10:59:30+00:00

Correct spelling typo in drivers/pci/hotplug. Signed-off-by: Masanari Iida Signed-off-by: Jiri Kosina