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Subject[PATCH v3 09/11] PCI Hotplug: restore fakephp interface with complete reimplementation
Date
From: Trent Piepho <xyzzy@speakeasy.org>

A complete re-implementation of fakephp is necessary if it is to
present its former interface (pre-2.6.27, when it broke). The
reason is that PCI hotplug drivers call pci_hp_register(), which
enforces the rule that only one /sys/bus/pci/slots/ file may be
created per physical slot.

The change breaks the old fakephp's assumption that it could
create a file per function. So we re-implement fakephp to avoid
using the standard PCI hotplug API so that we can restore the old
fakephp user interface.

It puts entries in /sys/bus/pci/slots with the names of all PCI
devices/functions, exactly symmetrical to what is shown in
/sys/bus/pci/devices. Each slots/ entry has a "power" attribute,
which works the same way as the fakephp driver's power attribute
has worked.

There are a few improvements over old fakephp, which couldn't handle
PCI devices being added or removed via a means outside of
fakephp's knowledge. If a device was added another way, old fakephp
didn't notice and didn't create the fake slot for it. If a
device was removed another way, old fakephp didn't delete the fake
slot for it (and accessing the stale slot caused an oops).

The new implementation overcomes these limitations. As a
consequence, removing a bridge with other devices behind it now
works as well, which is something else old fakephp couldn't do
previously.

This duplicates a tiny bit of the code in the PCI core that does
this same function. Re-using that code ends up being more
complex than duplicating it, and it makes code in the PCI core
more ugly just to support this legacy fakephp interface
compatibility layer.

[achiang@hp.com: rewrite changelog]
[achiang@hp.com: use pci_do_scan_bus()]
Reviewed-by: James Cameron <qz@hp.com>
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Alex Chiang <achiang@hp.com>
---

drivers/pci/hotplug/Makefile | 2
drivers/pci/hotplug/fakephp.c | 395 ----------------------------------
drivers/pci/hotplug/legacy_fakephp.c | 162 ++++++++++++++
3 files changed, 163 insertions(+), 396 deletions(-)
delete mode 100644 drivers/pci/hotplug/fakephp.c
create mode 100644 drivers/pci/hotplug/legacy_fakephp.c

diff --git a/drivers/pci/hotplug/Makefile b/drivers/pci/hotplug/Makefile
index 2aa117c..3314fe8 100644
--- a/drivers/pci/hotplug/Makefile
+++ b/drivers/pci/hotplug/Makefile
@@ -20,7 +20,7 @@ obj-$(CONFIG_HOTPLUG_PCI_RPA_DLPAR) += rpadlpar_io.o
obj-$(CONFIG_HOTPLUG_PCI_SGI) += sgi_hotplug.o

# Link this last so it doesn't claim devices that have a real hotplug driver
-obj-$(CONFIG_HOTPLUG_PCI_FAKE) += fakephp.o
+obj-$(CONFIG_HOTPLUG_PCI_FAKE) += legacy_fakephp.o

pci_hotplug-objs := pci_hotplug_core.o

diff --git a/drivers/pci/hotplug/fakephp.c b/drivers/pci/hotplug/fakephp.c
deleted file mode 100644
index d8649e1..0000000
--- a/drivers/pci/hotplug/fakephp.c
+++ /dev/null
@@ -1,395 +0,0 @@
-/*
- * Fake PCI Hot Plug Controller Driver
- *
- * Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
- * Copyright (C) 2003 IBM Corp.
- * Copyright (C) 2003 Rolf Eike Beer <eike-kernel@sf-tec.de>
- *
- * Based on ideas and code from:
- * Vladimir Kondratiev <vladimir.kondratiev@intel.com>
- * Rolf Eike Beer <eike-kernel@sf-tec.de>
- *
- * All rights reserved.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, version 2 of the License.
- *
- * Send feedback to <greg@kroah.com>
- */
-
-/*
- *
- * This driver will "emulate" removing PCI devices from the system. If
- * the "power" file is written to with "0" then the specified PCI device
- * will be completely removed from the kernel.
- *
- * WARNING, this does NOT turn off the power to the PCI device. This is
- * a "logical" removal, not a physical or electrical removal.
- *
- * Use this module at your own risk, you have been warned!
- *
- * Enabling PCI devices is left as an exercise for the reader...
- *
- */
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/pci.h>
-#include <linux/pci_hotplug.h>
-#include <linux/init.h>
-#include <linux/string.h>
-#include <linux/slab.h>
-#include <linux/workqueue.h>
-#include "../pci.h"
-
-#if !defined(MODULE)
- #define MY_NAME "fakephp"
-#else
- #define MY_NAME THIS_MODULE->name
-#endif
-
-#define dbg(format, arg...) \
- do { \
- if (debug) \
- printk(KERN_DEBUG "%s: " format, \
- MY_NAME , ## arg); \
- } while (0)
-#define err(format, arg...) printk(KERN_ERR "%s: " format, MY_NAME , ## arg)
-#define info(format, arg...) printk(KERN_INFO "%s: " format, MY_NAME , ## arg)
-
-#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@kroah.com>"
-#define DRIVER_DESC "Fake PCI Hot Plug Controller Driver"
-
-struct dummy_slot {
- struct list_head node;
- struct hotplug_slot *slot;
- struct pci_dev *dev;
- struct work_struct remove_work;
- unsigned long removed;
-};
-
-static int debug;
-static int dup_slots;
-static LIST_HEAD(slot_list);
-static struct workqueue_struct *dummyphp_wq;
-
-static void pci_rescan_worker(struct work_struct *work);
-static DECLARE_WORK(pci_rescan_work, pci_rescan_worker);
-
-static int enable_slot (struct hotplug_slot *slot);
-static int disable_slot (struct hotplug_slot *slot);
-
-static struct hotplug_slot_ops dummy_hotplug_slot_ops = {
- .owner = THIS_MODULE,
- .enable_slot = enable_slot,
- .disable_slot = disable_slot,
-};
-
-static void dummy_release(struct hotplug_slot *slot)
-{
- struct dummy_slot *dslot = slot->private;
-
- list_del(&dslot->node);
- kfree(dslot->slot->info);
- kfree(dslot->slot);
- pci_dev_put(dslot->dev);
- kfree(dslot);
-}
-
-#define SLOT_NAME_SIZE 8
-
-static int add_slot(struct pci_dev *dev)
-{
- struct dummy_slot *dslot;
- struct hotplug_slot *slot;
- char name[SLOT_NAME_SIZE];
- int retval = -ENOMEM;
- static int count = 1;
-
- slot = kzalloc(sizeof(struct hotplug_slot), GFP_KERNEL);
- if (!slot)
- goto error;
-
- slot->info = kzalloc(sizeof(struct hotplug_slot_info), GFP_KERNEL);
- if (!slot->info)
- goto error_slot;
-
- slot->info->power_status = 1;
- slot->info->max_bus_speed = PCI_SPEED_UNKNOWN;
- slot->info->cur_bus_speed = PCI_SPEED_UNKNOWN;
-
- dslot = kzalloc(sizeof(struct dummy_slot), GFP_KERNEL);
- if (!dslot)
- goto error_info;
-
- if (dup_slots)
- snprintf(name, SLOT_NAME_SIZE, "fake");
- else
- snprintf(name, SLOT_NAME_SIZE, "fake%d", count++);
- dbg("slot->name = %s\n", name);
- slot->ops = &dummy_hotplug_slot_ops;
- slot->release = &dummy_release;
- slot->private = dslot;
-
- retval = pci_hp_register(slot, dev->bus, PCI_SLOT(dev->devfn), name);
- if (retval) {
- err("pci_hp_register failed with error %d\n", retval);
- goto error_dslot;
- }
-
- dbg("slot->name = %s\n", hotplug_slot_name(slot));
- dslot->slot = slot;
- dslot->dev = pci_dev_get(dev);
- list_add (&dslot->node, &slot_list);
- return retval;
-
-error_dslot:
- kfree(dslot);
-error_info:
- kfree(slot->info);
-error_slot:
- kfree(slot);
-error:
- return retval;
-}
-
-static int __init pci_scan_buses(void)
-{
- struct pci_dev *dev = NULL;
- int lastslot = 0;
-
- while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
- if (PCI_FUNC(dev->devfn) > 0 &&
- lastslot == PCI_SLOT(dev->devfn))
- continue;
- lastslot = PCI_SLOT(dev->devfn);
- add_slot(dev);
- }
-
- return 0;
-}
-
-static void remove_slot(struct dummy_slot *dslot)
-{
- int retval;
-
- dbg("removing slot %s\n", hotplug_slot_name(dslot->slot));
- retval = pci_hp_deregister(dslot->slot);
- if (retval)
- err("Problem unregistering a slot %s\n",
- hotplug_slot_name(dslot->slot));
-}
-
-/* called from the single-threaded workqueue handler to remove a slot */
-static void remove_slot_worker(struct work_struct *work)
-{
- struct dummy_slot *dslot =
- container_of(work, struct dummy_slot, remove_work);
- remove_slot(dslot);
-}
-
-/**
- * pci_rescan_slot - Rescan slot
- * @temp: Device template. Should be set: bus and devfn.
- *
- * Tries hard not to re-enable already existing devices;
- * also handles scanning of subfunctions.
- */
-static int pci_rescan_slot(struct pci_dev *temp)
-{
- struct pci_bus *bus = temp->bus;
- struct pci_dev *dev;
- int func;
- u8 hdr_type;
- int count = 0;
-
- if (!pci_read_config_byte(temp, PCI_HEADER_TYPE, &hdr_type)) {
- temp->hdr_type = hdr_type & 0x7f;
- if ((dev = pci_get_slot(bus, temp->devfn)) != NULL)
- pci_dev_put(dev);
- else {
- dev = pci_scan_single_device(bus, temp->devfn);
- if (dev) {
- dbg("New device on %s function %x:%x\n",
- bus->name, temp->devfn >> 3,
- temp->devfn & 7);
- count++;
- }
- }
- /* multifunction device? */
- if (!(hdr_type & 0x80))
- return count;
-
- /* continue scanning for other functions */
- for (func = 1, temp->devfn++; func < 8; func++, temp->devfn++) {
- if (pci_read_config_byte(temp, PCI_HEADER_TYPE, &hdr_type))
- continue;
- temp->hdr_type = hdr_type & 0x7f;
-
- if ((dev = pci_get_slot(bus, temp->devfn)) != NULL)
- pci_dev_put(dev);
- else {
- dev = pci_scan_single_device(bus, temp->devfn);
- if (dev) {
- dbg("New device on %s function %x:%x\n",
- bus->name, temp->devfn >> 3,
- temp->devfn & 7);
- count++;
- }
- }
- }
- }
-
- return count;
-}
-
-
-/**
- * pci_rescan_bus - Rescan PCI bus
- * @bus: the PCI bus to rescan
- *
- * Call pci_rescan_slot for each possible function of the bus.
- */
-static void pci_rescan_bus(const struct pci_bus *bus)
-{
- unsigned int devfn;
- struct pci_dev *dev;
- int retval;
- int found = 0;
- dev = alloc_pci_dev();
- if (!dev)
- return;
-
- dev->bus = (struct pci_bus*)bus;
- dev->sysdata = bus->sysdata;
- for (devfn = 0; devfn < 0x100; devfn += 8) {
- dev->devfn = devfn;
- found += pci_rescan_slot(dev);
- }
-
- if (found) {
- pci_bus_assign_resources(bus);
- list_for_each_entry(dev, &bus->devices, bus_list) {
- /* Skip already-added devices */
- if (dev->is_added)
- continue;
- retval = pci_bus_add_device(dev);
- if (retval)
- dev_err(&dev->dev,
- "Error adding device, continuing\n");
- else
- add_slot(dev);
- }
- pci_bus_add_devices(bus);
- }
- kfree(dev);
-}
-
-/* recursively scan all buses */
-static void pci_rescan_buses(const struct list_head *list)
-{
- const struct list_head *l;
- list_for_each(l,list) {
- const struct pci_bus *b = pci_bus_b(l);
- pci_rescan_bus(b);
- pci_rescan_buses(&b->children);
- }
-}
-
-/* initiate rescan of all pci buses */
-static inline void pci_rescan(void) {
- pci_rescan_buses(&pci_root_buses);
-}
-
-/* called from the single-threaded workqueue handler to rescan all pci buses */
-static void pci_rescan_worker(struct work_struct *work)
-{
- pci_rescan();
-}
-
-static int enable_slot(struct hotplug_slot *hotplug_slot)
-{
- /* mis-use enable_slot for rescanning of the pci bus */
- cancel_work_sync(&pci_rescan_work);
- queue_work(dummyphp_wq, &pci_rescan_work);
- return 0;
-}
-
-static int disable_slot(struct hotplug_slot *slot)
-{
- struct dummy_slot *dslot;
- struct pci_dev *dev;
- int func;
-
- if (!slot)
- return -ENODEV;
- dslot = slot->private;
-
- dbg("%s - physical_slot = %s\n", __func__, hotplug_slot_name(slot));
-
- for (func = 7; func >= 0; func--) {
- dev = pci_get_slot(dslot->dev->bus, dslot->dev->devfn + func);
- if (!dev)
- continue;
-
- if (test_and_set_bit(0, &dslot->removed)) {
- dbg("Slot already scheduled for removal\n");
- pci_dev_put(dev);
- return -ENODEV;
- }
-
- /* remove the device from the pci core */
- pci_remove_bus_device(dev);
-
- /* queue work item to blow away this sysfs entry and other
- * parts.
- */
- INIT_WORK(&dslot->remove_work, remove_slot_worker);
- queue_work(dummyphp_wq, &dslot->remove_work);
-
- pci_dev_put(dev);
- }
- return 0;
-}
-
-static void cleanup_slots (void)
-{
- struct list_head *tmp;
- struct list_head *next;
- struct dummy_slot *dslot;
-
- destroy_workqueue(dummyphp_wq);
- list_for_each_safe (tmp, next, &slot_list) {
- dslot = list_entry (tmp, struct dummy_slot, node);
- remove_slot(dslot);
- }
-
-}
-
-static int __init dummyphp_init(void)
-{
- info(DRIVER_DESC "\n");
-
- dummyphp_wq = create_singlethread_workqueue(MY_NAME);
- if (!dummyphp_wq)
- return -ENOMEM;
-
- return pci_scan_buses();
-}
-
-
-static void __exit dummyphp_exit(void)
-{
- cleanup_slots();
-}
-
-module_init(dummyphp_init);
-module_exit(dummyphp_exit);
-
-MODULE_AUTHOR(DRIVER_AUTHOR);
-MODULE_DESCRIPTION(DRIVER_DESC);
-MODULE_LICENSE("GPL");
-module_param(debug, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(debug, "Debugging mode enabled or not");
-module_param(dup_slots, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(dup_slots, "Force duplicate slot names for debugging");
diff --git a/drivers/pci/hotplug/legacy_fakephp.c b/drivers/pci/hotplug/legacy_fakephp.c
new file mode 100644
index 0000000..e75af9e
--- /dev/null
+++ b/drivers/pci/hotplug/legacy_fakephp.c
@@ -0,0 +1,162 @@
+/* Works like the fakephp driver used to, except a little better.
+ *
+ * - It's possible to remove devices with subordinate busses.
+ * - New PCI devices that appear via any method, not just a fakephp triggered
+ * rescan, will be noticed.
+ * - Devices that are removed via any method, not just a fakephp triggered
+ * removal, will also be noticed.
+ *
+ * Uses nothing from the pci-hotplug subsystem.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+#include "../pci.h"
+
+struct legacy_slot {
+ struct kobject kobj;
+ struct pci_dev *dev;
+ struct list_head list;
+};
+
+static LIST_HEAD(legacy_list);
+
+static ssize_t legacy_show(struct kobject *kobj, struct attribute *attr,
+ char *buf)
+{
+ struct legacy_slot *slot = container_of(kobj, typeof(*slot), kobj);
+ strcpy(buf, "1\n");
+ return 2;
+}
+
+static void remove_callback(void *data)
+{
+ pci_remove_bus_device((struct pci_dev *)data);
+}
+
+static ssize_t legacy_store(struct kobject *kobj, struct attribute *attr,
+ const char *buf, size_t len)
+{
+ struct legacy_slot *slot = container_of(kobj, typeof(*slot), kobj);
+ unsigned long val;
+
+ if (strict_strtoul(buf, 0, &val) < 0)
+ return -EINVAL;
+
+ if (val)
+ pci_do_scan_bus(slot->dev->bus);
+ else
+ sysfs_schedule_callback(&slot->dev->dev.kobj, remove_callback,
+ slot->dev, THIS_MODULE);
+ return len;
+}
+
+static struct attribute *legacy_attrs[] = {
+ &(struct attribute){ .name = "power", .mode = 0644 },
+ NULL,
+};
+
+static void legacy_release(struct kobject *kobj)
+{
+ struct legacy_slot *slot = container_of(kobj, typeof(*slot), kobj);
+
+ pci_dev_put(slot->dev);
+ kfree(slot);
+}
+
+static struct kobj_type legacy_ktype = {
+ .sysfs_ops = &(struct sysfs_ops){
+ .store = legacy_store, .show = legacy_show
+ },
+ .release = &legacy_release,
+ .default_attrs = legacy_attrs,
+};
+
+static int legacy_add_slot(struct pci_dev *pdev)
+{
+ struct legacy_slot *slot = kzalloc(sizeof(*slot), GFP_KERNEL);
+
+ if (!slot)
+ return -ENOMEM;
+
+ if (kobject_init_and_add(&slot->kobj, &legacy_ktype,
+ &pci_slots_kset->kobj, "%s",
+ pdev->dev.bus_id)) {
+ dev_warn(&pdev->dev, "Failed to created legacy fake slot\n");
+ return -EINVAL;
+ }
+ slot->dev = pci_dev_get(pdev);
+
+ list_add(&slot->list, &legacy_list);
+
+ return 0;
+}
+
+static int legacy_notify(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct pci_dev *pdev = to_pci_dev(data);
+
+ if (action == BUS_NOTIFY_ADD_DEVICE) {
+ legacy_add_slot(pdev);
+ } else if (action == BUS_NOTIFY_DEL_DEVICE) {
+ struct legacy_slot *slot;
+
+ list_for_each_entry(slot, &legacy_list, list)
+ if (slot->dev == pdev)
+ goto found;
+
+ dev_warn(&pdev->dev, "Missing legacy fake slot?");
+ return -ENODEV;
+found:
+ kobject_del(&slot->kobj);
+ list_del(&slot->list);
+ kobject_put(&slot->kobj);
+ }
+
+ return 0;
+}
+
+static struct notifier_block legacy_notifier = {
+ .notifier_call = legacy_notify
+};
+
+static int __init init_legacy(void)
+{
+ struct pci_dev *pdev = NULL;
+
+ /* Add existing devices */
+ while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev)))
+ legacy_add_slot(pdev);
+
+ /* Be alerted of any new ones */
+ bus_register_notifier(&pci_bus_type, &legacy_notifier);
+ return 0;
+}
+module_init(init_legacy);
+
+static void __exit remove_legacy(void)
+{
+ struct legacy_slot *slot, *tmp;
+
+ bus_unregister_notifier(&pci_bus_type, &legacy_notifier);
+
+ list_for_each_entry_safe(slot, tmp, &legacy_list, list) {
+ list_del(&slot->list);
+ kobject_del(&slot->kobj);
+ kobject_put(&slot->kobj);
+ }
+}
+module_exit(remove_legacy);
+
+
+MODULE_AUTHOR("Trent Piepho <xyzzy@speakeasy.org>");
+MODULE_DESCRIPTION("Legacy version of the fakephp interface");
+MODULE_LICENSE("GPL");


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