[PATCH 3/3] PCI: Legacy fakephp driver

[Trent Piepho]

This module's interface is compatible with what fakephp's interface has
been.

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

There are a few improvements over fakephp, which couldn't handle PCI
devices being added or removed via a means other than fakephp's actions.
If a device is added another way, fakephp doesn't notice it and doesn't
create the fake slot for it.  If a device was removed another way, fakephp
doesn't delete the fake slot for it (and accessing the stale slot will
cause an oops).  These problems are fixed.  As a consequence of this,
removing a bridge with other devices behind it works as well, which is
something else fakephp couldn't do.

This patch 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.
---
 drivers/pci/hotplug/Kconfig          |    5 +
 drivers/pci/hotplug/Makefile         |    1 +
 drivers/pci/hotplug/legacy_fakephp.c |  168 ++++++++++++++++++++++++++++++++++
 3 files changed, 174 insertions(+), 0 deletions(-)
 create mode 100644 drivers/pci/hotplug/legacy_fakephp.c

diff --git a/drivers/pci/hotplug/Kconfig b/drivers/pci/hotplug/Kconfig
index eacfb13..d26bc68 100644
--- a/drivers/pci/hotplug/Kconfig
+++ b/drivers/pci/hotplug/Kconfig
@@ -39,6 +39,11 @@ config HOTPLUG_PCI_FAKE
 
 	  When in doubt, say N.
 
+config HOTPLUG_PCI_LEGACY_FAKE
+	tristate "Legacy Fake PCI Hotplug driver"
+	help
+	  Provides an interface like the fakephp driver used to.
+
 config HOTPLUG_PCI_COMPAQ
 	tristate "Compaq PCI Hotplug driver"
 	depends on X86 && PCI_BIOS && PCI_LEGACY
diff --git a/drivers/pci/hotplug/Makefile b/drivers/pci/hotplug/Makefile
index 9bdbe1a..9ad009d 100644
--- a/drivers/pci/hotplug/Makefile
+++ b/drivers/pci/hotplug/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_HOTPLUG_PCI_SHPC)		+= shpchp.o
 obj-$(CONFIG_HOTPLUG_PCI_RPA)		+= rpaphp.o
 obj-$(CONFIG_HOTPLUG_PCI_RPA_DLPAR)	+= rpadlpar_io.o
 obj-$(CONFIG_HOTPLUG_PCI_SGI)		+= sgi_hotplug.o
+obj-$(CONFIG_HOTPLUG_PCI_LEGACY_FAKE)	+= legacy_fakephp.o
 
 # Link this last so it doesn't claim devices that have a real hotplug driver
 obj-$(CONFIG_HOTPLUG_PCI_FAKE)		+= fakephp.o
diff --git a/drivers/pci/hotplug/legacy_fakephp.c b/drivers/pci/hotplug/legacy_fakephp.c
new file mode 100644
index 0000000..696b156
--- /dev/null
+++ b/drivers/pci/hotplug/legacy_fakephp.c
@@ -0,0 +1,168 @@
+/* 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);
+}
+
+/* pci_rescan_busses is __devinit, which is why this driver requires HOTPLUG to
+ * be on.  */
+static void __ref rescan(void)
+{
+	pci_rescan_busses();
+}
+
+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)
+		rescan();
+	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@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Legacy version of the fakephp interface");
+MODULE_LICENSE("GPL");
-- 
1.5.4.3

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