[RFC] consolidate /sbin/hotplug call for pci and usb

[Greg KH <greg@kroah.com>]

Hi all,

Here's a patch against 2.5.38 that does the following:
	- adds a call to /sbin/hotplug to the driver core
	- removes the call to /sbin/hotplug from the pci and usb cores
	- adds a callback to the struct bus_type for the driver core to
	  use to set up bus specific /sbin/hotplug arguments.

One nice side effect of this patch, is that all iterfaces for a USB
device generate a call to /sbin/hotplug, so complex devices should now
be properly recognized by userspace much easier.

I've successfully tested this with both PCI Hotplug systems, and USB
devices.  There is still a bug remaining that causes an oops when a USB
pci controller is unloaded from the system that I am still tracking
down.  After I find this problem, and if there are no complaints, I'll
send it on to Linus.

Comments appreciated.

thanks,

greg k-h


diff -Nru a/drivers/base/Makefile b/drivers/base/Makefile
--- a/drivers/base/Makefile	Wed Sep 25 14:22:28 2002
+++ b/drivers/base/Makefile	Wed Sep 25 14:22:28 2002
@@ -5,6 +5,10 @@
 
 obj-y		+= fs/
 
+ifeq ($(CONFIG_HOTPLUG),y)
+	obj-y	+= hotplug.o
+endif
+
 export-objs	:= core.o power.o sys.o bus.o driver.o \
 			class.o intf.o
 
diff -Nru a/drivers/base/base.h b/drivers/base/base.h
--- a/drivers/base/base.h	Wed Sep 25 14:22:28 2002
+++ b/drivers/base/base.h	Wed Sep 25 14:22:28 2002
@@ -50,3 +50,13 @@
 
 extern int driver_attach(struct device_driver * drv);
 extern void driver_detach(struct device_driver * drv);
+
+#ifdef CONFIG_HOTPLUG
+extern int dev_hotplug(struct device *dev, const char *action);
+#else
+static inline int dev_hotplug(struct device *dev, const char *action)
+{
+	return 0;
+}
+#endif
+
diff -Nru a/drivers/base/core.c b/drivers/base/core.c
--- a/drivers/base/core.c	Wed Sep 25 14:22:28 2002
+++ b/drivers/base/core.c	Wed Sep 25 14:22:28 2002
@@ -198,6 +198,9 @@
 	if (platform_notify)
 		platform_notify(dev);
 
+	/* notify userspace of device entry */
+	dev_hotplug(dev, "add");
+
  register_done:
 	if (error) {
 		spin_lock(&device_lock);
@@ -255,6 +258,9 @@
 
 	device_detach(dev);
 	bus_remove_device(dev);
+
+	/* notify userspace that this device just disappeared */
+	dev_hotplug (dev, "remove");
 
 	/* remove the driverfs directory */
 	device_remove_dir(dev);
diff -Nru a/drivers/base/hotplug.c b/drivers/base/hotplug.c
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/drivers/base/hotplug.c	Wed Sep 25 14:22:28 2002
@@ -0,0 +1,114 @@
+/*
+ * drivers/base/hotplug.c - hotplug call code
+ * 
+ * Copyright (c) 2002 Greg Kroah-Hartman <greg@kroah.com>
+ *		 2002 IBM Corp.
+ */
+
+#define DEBUG 0
+
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/kmod.h>
+#include <linux/interrupt.h>
+#include "base.h"
+
+/*
+ * hotplugging invokes what /proc/sys/kernel/hotplug says (normally
+ * /sbin/hotplug) when devices get added or removed.
+ *
+ * This invokes a user mode policy agent, typically helping to load driver
+ * or other modules, configure the device, and more.  Drivers can provide
+ * a MODULE_DEVICE_TABLE to help with module loading subtasks.
+ *
+ * Some synchronization is important: removes can't start processing
+ * before the add-device processing completes, and vice versa.  That keeps
+ * a stack of USB-related identifiers stable while they're in use.  If we
+ * know that agents won't complete after they return (such as by forking
+ * a process that completes later), it's enough to just waitpid() for the
+ * agent -- as is currently done.
+ *
+ * The reason: we know we're called either from khubd (the typical case)
+ * or from root hub initialization (init, kapmd, modprobe, etc).  In both
+ * cases, we know no other thread can recycle our address, since we must
+ * already have been serialized enough to prevent that.
+ */
+#define BUFFER_SIZE	1024	/* should be enough memory for the env */
+#define NUM_ENVP	32	/* number of env pointers */
+int dev_hotplug (struct device *dev, const char *action)
+{
+	char *argv [3], **envp, *buffer, *scratch;
+	int retval;
+	int i = 0;
+
+	pr_debug ("%s\n", __FUNCTION__);
+	if (!dev)
+		return -ENODEV;
+
+	if (!dev->bus || !dev->bus->hotplug)
+		return -ENODEV;
+
+	if (!hotplug_path [0])
+		return -ENODEV;
+
+	if (in_interrupt ()) {
+		pr_debug ("%s - in_interrupt, not allowed!", __FUNCTION__);
+		return -EIO;
+	}
+
+	if (!current->fs->root) {
+		/* don't try to do anything unless we have a root partition */
+		pr_debug ("%s - %s -- no FS yet\n", __FUNCTION__, action);
+		return -EIO;
+	}
+
+	envp = (char **) kmalloc (NUM_ENVP * sizeof (char *), GFP_KERNEL);
+	if (!envp)
+		return -ENOMEM;
+
+	buffer = kmalloc (BUFFER_SIZE, GFP_KERNEL);
+	if (!buffer) {
+		kfree (envp);
+		return -ENOMEM;
+	}
+
+	/* only one standardized param to hotplug command: the bus name */
+	argv [0] = hotplug_path;
+	argv [1] = dev->bus->name;
+	argv [2] = 0;
+
+	/* minimal command environment */
+	envp [i++] = "HOME=/";
+	envp [i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+
+#ifdef DEBUG
+	/* hint that policy agent should enter no-stdout debug mode */
+	envp [i++] = "DEBUG=kernel";
+#endif
+
+	scratch = buffer;
+	/* action:  add, remove */
+	envp [i++] = scratch;
+	scratch += sprintf (scratch, "ACTION=%s", action) + 1;
+
+	/* have the bus specific function set up the rest of the environment */
+	retval = dev->bus->hotplug (dev, &envp[i], NUM_ENVP - i,
+				    scratch, BUFFER_SIZE - (scratch - buffer));
+	if (retval) {
+		pr_debug ("%s - hotplug() returned %d\n", __FUNCTION__, retval);
+		goto exit;
+	}
+
+	pr_debug ("%s: %s %s %s %s %s %s\n", __FUNCTION__, argv [0], argv[1],
+		  action, envp[0], envp[1], envp[2]);
+	retval = call_usermodehelper (argv [0], argv, envp);
+	if (retval)
+		pr_debug ("%s - call_usermodehelper returned %d\n",
+			  __FUNCTION__, retval);
+
+exit:
+	kfree (buffer);
+	kfree (envp);
+	return retval;
+}
diff -Nru a/drivers/pci/hotplug.c b/drivers/pci/hotplug.c
--- a/drivers/pci/hotplug.c	Wed Sep 25 14:22:28 2002
+++ b/drivers/pci/hotplug.c	Wed Sep 25 14:22:28 2002
@@ -1,52 +1,42 @@
 #include <linux/pci.h>
 #include <linux/module.h>
 #include <linux/kmod.h>		/* for hotplug_path */
+#include "pci.h"
 
-#ifndef FALSE
-#define FALSE	(0)
-#define TRUE	(!FALSE)
-#endif
 
 #ifdef CONFIG_HOTPLUG
-static void run_sbin_hotplug(struct pci_dev *pdev, int insert)
+int pci_hotplug (struct device *dev, char **envp, int num_envp,
+		 char *buffer, int buffer_size)
 {
-	int i;
-	char *argv[3], *envp[8];
-	char id[20], sub_id[24], bus_id[24], class_id[20];
-
-	if (!hotplug_path[0])
-		return;
-
-	sprintf(class_id, "PCI_CLASS=%04X", pdev->class);
-	sprintf(id, "PCI_ID=%04X:%04X", pdev->vendor, pdev->device);
-	sprintf(sub_id, "PCI_SUBSYS_ID=%04X:%04X", pdev->subsystem_vendor, pdev->subsystem_device);
-	sprintf(bus_id, "PCI_SLOT_NAME=%s", pdev->slot_name);
-
-	i = 0;
-	argv[i++] = hotplug_path;
-	argv[i++] = "pci";
-	argv[i] = 0;
-
-	i = 0;
-	/* minimal command environment */
-	envp[i++] = "HOME=/";
-	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
-	
-	/* other stuff we want to pass to /sbin/hotplug */
-	envp[i++] = class_id;
-	envp[i++] = id;
-	envp[i++] = sub_id;
-	envp[i++] = bus_id;
-	if (insert)
-		envp[i++] = "ACTION=add";
-	else
-		envp[i++] = "ACTION=remove";
+	struct pci_dev *pdev = to_pci_dev(dev);
+	char *scratch;
+	int i = 0;
+
+	scratch = buffer;
+
+	/* stuff we want to pass to /sbin/hotplug */
+	envp[i++] = scratch;
+	scratch += sprintf (scratch, "PCI_CLASS=%04X", pdev->class) + 1;
+
+	envp[i++] = scratch;
+	scratch += sprintf (scratch, "PCI_ID=%04X:%04X",
+			    pdev->vendor, pdev->device) + 1;
+	envp[i++] = scratch;
+	scratch += sprintf (scratch, "PCI_SUBSYS_ID=%04X:%04X",
+			    pdev->subsystem_vendor, pdev->subsystem_device) + 1;
+	envp[i++] = scratch;
+	scratch += sprintf (scratch, "PCI_SLOT_NAME=%s", pdev->slot_name) + 1;
 	envp[i] = 0;
 
-	call_usermodehelper (argv [0], argv, envp);
+	/* check to see if we went over buffer? */
+	return 0;
 }
 #else
-static void run_sbin_hotplug(struct pci_dev *pdev, int insert) { }
+int pci_hotplug (struct device *dev, char **envp, int num_envp,
+		 char *buffer, int buffer_size)
+{
+	return -ENODEV;
+}
 #endif
 
 /**
@@ -66,8 +56,6 @@
 #ifdef CONFIG_PROC_FS
 	pci_proc_attach_device(dev);
 #endif
-	/* notify userspace of new hotplug device */
-	run_sbin_hotplug(dev, TRUE);
 }
 
 static void
@@ -99,8 +87,6 @@
 #ifdef CONFIG_PROC_FS
 	pci_proc_detach_device(dev);
 #endif
-	/* notify userspace of hotplug device removal */
-	run_sbin_hotplug(dev, FALSE);
 }
 
 #ifdef CONFIG_HOTPLUG
diff -Nru a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
--- a/drivers/pci/pci-driver.c	Wed Sep 25 14:22:28 2002
+++ b/drivers/pci/pci-driver.c	Wed Sep 25 14:22:28 2002
@@ -6,6 +6,7 @@
 #include <linux/pci.h>
 #include <linux/module.h>
 #include <linux/init.h>
+#include "pci.h"
 
 /*
  *  Registration of PCI drivers and handling of hot-pluggable devices.
@@ -199,8 +200,9 @@
 }
 
 struct bus_type pci_bus_type = {
-	name:	"pci",
-	match:	pci_bus_match,
+	name:		"pci",
+	match:		pci_bus_match,
+	hotplug:	pci_hotplug,
 };
 
 static int __init pci_driver_init(void)
diff -Nru a/drivers/pci/pci.h b/drivers/pci/pci.h
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/drivers/pci/pci.h	Wed Sep 25 14:22:28 2002
@@ -0,0 +1,5 @@
+/* Functions internal to the PCI core code */
+
+extern int pci_hotplug (struct device *dev, char **envp, int num_envp,
+			 char *buffer, int buffer_size);
+
diff -Nru a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
--- a/drivers/usb/core/usb.c	Wed Sep 25 14:22:28 2002
+++ b/drivers/usb/core/usb.c	Wed Sep 25 14:22:28 2002
@@ -505,57 +505,41 @@
  * cases, we know no other thread can recycle our address, since we must
  * already have been serialized enough to prevent that.
  */
-static void call_policy (char *verb, struct usb_device *dev)
+static int usb_hotplug (struct device *dev, char **envp, int num_envp,
+			char *buffer, int buffer_size)
 {
-	char *argv [3], **envp, *buf, *scratch;
-	int i = 0, value;
+	struct usb_interface *intf;
+	struct usb_device *usb_dev;
+	char *scratch;
+	int i = 0;
 
-	if (!hotplug_path [0])
-		return;
-	if (in_interrupt ()) {
-		dbg ("In_interrupt");
-		return;
-	}
-	if (!current->fs->root) {
-		/* statically linked USB is initted rather early */
-		dbg ("call_policy %s, num %d -- no FS yet", verb, dev->devnum);
-		return;
-	}
-	if (dev->devnum < 0) {
+	dbg ("%s", __FUNCTION__);
+
+	if (!dev)
+		return -ENODEV;
+
+	/* check for generic driver, we do not call do hotplug calls for it */
+	if (dev->driver == &usb_generic_driver)
+		return -ENODEV;
+
+	intf = to_usb_interface(dev);
+	if (!intf)
+		return -ENODEV;
+
+	usb_dev = interface_to_usbdev (intf);
+	if (!usb_dev)
+		return -ENODEV;
+	
+	if (usb_dev->devnum < 0) {
 		dbg ("device already deleted ??");
-		return;
+		return -ENODEV;
 	}
-	if (!(envp = (char **) kmalloc (20 * sizeof (char *), GFP_KERNEL))) {
-		dbg ("enomem");
-		return;
-	}
-	if (!(buf = kmalloc (256, GFP_KERNEL))) {
-		kfree (envp);
-		dbg ("enomem2");
-		return;
+	if (!usb_dev->bus) {
+		dbg ("bus already removed?");
+		return -ENODEV;
 	}
 
-	/* only one standardized param to hotplug command: type */
-	argv [0] = hotplug_path;
-	argv [1] = "usb";
-	argv [2] = 0;
-
-	/* minimal command environment */
-	envp [i++] = "HOME=/";
-	envp [i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
-
-#ifdef	DEBUG
-	/* hint that policy agent should enter no-stdout debug mode */
-	envp [i++] = "DEBUG=kernel";
-#endif
-	/* extensible set of named bus-specific parameters,
-	 * supporting multiple driver selection algorithms.
-	 */
-	scratch = buf;
-
-	/* action:  add, remove */
-	envp [i++] = scratch;
-	scratch += sprintf (scratch, "ACTION=%s", verb) + 1;
+	scratch = buffer;
 
 #ifdef	CONFIG_USB_DEVICEFS
 	/* If this is available, userspace programs can directly read
@@ -565,26 +549,35 @@
 	 * FIXME reduce hardwired intelligence here
 	 */
 	envp [i++] = "DEVFS=/proc/bus/usb";
+	if (i >= num_envp)
+		return -ENOMEM;
+
 	envp [i++] = scratch;
 	scratch += sprintf (scratch, "DEVICE=/proc/bus/usb/%03d/%03d",
-		dev->bus->busnum, dev->devnum) + 1;
+		usb_dev->bus->busnum, usb_dev->devnum) + 1;
+	if (i >= num_envp)
+		return -ENOMEM;
 #endif
-
 	/* per-device configuration hacks are common */
 	envp [i++] = scratch;
 	scratch += sprintf (scratch, "PRODUCT=%x/%x/%x",
-		dev->descriptor.idVendor,
-		dev->descriptor.idProduct,
-		dev->descriptor.bcdDevice) + 1;
+		usb_dev->descriptor.idVendor,
+		usb_dev->descriptor.idProduct,
+		usb_dev->descriptor.bcdDevice) + 1;
+	if (i >= num_envp)
+		return -ENOMEM;
 
 	/* class-based driver binding models */
 	envp [i++] = scratch;
 	scratch += sprintf (scratch, "TYPE=%d/%d/%d",
-			    dev->descriptor.bDeviceClass,
-			    dev->descriptor.bDeviceSubClass,
-			    dev->descriptor.bDeviceProtocol) + 1;
-	if (dev->descriptor.bDeviceClass == 0) {
-		int alt = dev->actconfig->interface [0].act_altsetting;
+			    usb_dev->descriptor.bDeviceClass,
+			    usb_dev->descriptor.bDeviceSubClass,
+			    usb_dev->descriptor.bDeviceProtocol) + 1;
+	if (i >= num_envp)
+		return -ENOMEM;
+
+	if (usb_dev->descriptor.bDeviceClass == 0) {
+		int alt = intf->act_altsetting;
 
 		/* a simple/common case: one config, one interface, one driver
 		 * with current altsetting being a reasonable setting.
@@ -593,30 +586,27 @@
 		 */
 		envp [i++] = scratch;
 		scratch += sprintf (scratch, "INTERFACE=%d/%d/%d",
-			dev->actconfig->interface [0].altsetting [alt].bInterfaceClass,
-			dev->actconfig->interface [0].altsetting [alt].bInterfaceSubClass,
-			dev->actconfig->interface [0].altsetting [alt].bInterfaceProtocol)
+			intf->altsetting[alt].bInterfaceClass,
+			intf->altsetting[alt].bInterfaceSubClass,
+			intf->altsetting[alt].bInterfaceProtocol)
 			+ 1;
-		/* INTERFACE-0, INTERFACE-1, ... ? */
+		if (i >= num_envp)
+			return -ENOMEM;
+
 	}
 	envp [i++] = 0;
-	/* assert: (scratch - buf) < sizeof buf */
+	/* assert: (scratch - buffer) < buffer_size */
 
-	/* NOTE: user mode daemons can call the agents too */
-
-	dbg ("kusbd: %s %s %d", argv [0], verb, dev->devnum);
-	value = call_usermodehelper (argv [0], argv, envp);
-	kfree (buf);
-	kfree (envp);
-	if (value != 0)
-		dbg ("kusbd policy returned 0x%x", value);
+	return 0;
 }
 
 #else
 
-static inline void
-call_policy (char *verb, struct usb_device *dev)
-{ } 
+static int usb_hotplug (struct device *dev, char **envp,
+			char *buffer, int buffer_size)
+{
+	return -ENODEV;
+}
 
 #endif	/* CONFIG_HOTPLUG */
 
@@ -889,9 +879,6 @@
 		put_device(&dev->dev);
 	}
 
-	/* Let policy agent unload modules etc */
-	call_policy ("remove", dev);
-
 	/* Decrement the reference count, it'll auto free everything when */
 	/* it hits 0 which could very well be now */
 	usb_put_dev(dev);
@@ -1169,9 +1156,6 @@
 	/* add a /proc/bus/usb entry */
 	usbfs_add_device(dev);
 
-	/* userspace may load modules and/or configure further */
-	call_policy ("add", dev);
-
 	return 0;
 }
 
@@ -1434,6 +1418,7 @@
 struct bus_type usb_bus_type = {
 	.name =		"usb",
 	.match =	usb_device_match,
+	.hotplug =	usb_hotplug,
 };
 
 /*
diff -Nru a/include/linux/device.h b/include/linux/device.h
--- a/include/linux/device.h	Wed Sep 25 14:22:28 2002
+++ b/include/linux/device.h	Wed Sep 25 14:22:28 2002
@@ -67,6 +67,8 @@
 
 	int		(*match)(struct device * dev, struct device_driver * drv);
 	struct device * (*add)	(struct device * parent, char * bus_id);
+	int		(*hotplug) (struct device *dev, char **envp, 
+				    int num_envp, char *buffer, int buffer_size);
 };