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Subject[RFC PATCH 07/10] 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.

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 | 385 ----------------------------------
drivers/pci/hotplug/legacy_fakephp.c | 163 ++++++++++++++
3 files changed, 164 insertions(+), 386 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 e31fb91..5a86728 100644
--- a/drivers/pci/hotplug/Makefile
+++ b/drivers/pci/hotplug/Makefile
@@ -16,7 +16,7 @@ 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 b0e7de9..0000000
--- a/drivers/pci/hotplug/fakephp.c
+++ /dev/null
@@ -1,385 +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 void pci_rescan_slot(struct pci_dev *temp)
-{
- struct pci_bus *bus = temp->bus;
- struct pci_dev *dev;
- int func;
- int retval;
- u8 hdr_type;
-
- 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);
- retval = pci_bus_add_device(dev);
- if (retval)
- dev_err(&dev->dev, "error adding "
- "device, continuing.\n");
- else
- add_slot(dev);
- }
- }
- /* multifunction device? */
- if (!(hdr_type & 0x80))
- return;
-
- /* 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);
- retval = pci_bus_add_device(dev);
- if (retval)
- dev_err(&dev->dev, "error adding "
- "device, continuing.\n");
- else
- add_slot(dev);
- }
- }
- }
- }
-}
-
-
-/**
- * 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;
- 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;
- pci_rescan_slot(dev);
- }
- 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..185cb67
--- /dev/null
+++ b/drivers/pci/hotplug/legacy_fakephp.c
@@ -0,0 +1,163 @@
+/* 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_scan_child_bus(slot->dev->bus);
+ pci_bus_add_devices(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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