Re: put "device" symlink into hotplug environment?

[Kay Sievers <kay.sievers@vrfy.org>]

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On Thu, Nov 04, 2004 at 12:39:59AM +0100, Kay Sievers wrote:
> Hi Greg,
> what if we put the sysfs path of the physical device into the hotplug
> environment? All virtual devices will not have the key. This would solve
> all the wait for the "device" link issues and we can throw away one of
> the exception lists as the kernel will tell us if it is going to create
> a symlink.
> 
> I get hotplug events like this now:
> 
> physical backed device:
>   ACTION=add
>   SUBSYSTEM=net
>   DEVPATH=/class/net/eth0
>   DEVSYSDEV=/devices/pci0000:00/0000:00:1e.0/0000:02:01.0
>   INTERFACE=eth0
>   SEQNUM=966
>   PATH=/sbin:/bin:/usr/sbin:/usr/bin
>   HOME=/
> 
> virtual:
>   ACTION=add
>   SUBSYSTEM=net
>   DEVPATH=/class/net/dummy0
>   INTERFACE=dummy0
>   SEQNUM=977
>   PATH=/sbin:/bin:/usr/sbin:/usr/bin
>   HOME=/

We can also pass the BUS together with the class device. The search
for the BUS value is an expensive tasks in udev, cause we need to
reverse lookup the whole /sys/bus directory to find the symlink to our
physical device.

This is my pci network card again:
  ACTION=add
  SUBSYSTEM=net
  DEVPATH=/class/net/eth0
  DEVPHYSDEV=/devices/pci0000:00/0000:00:1e.0/0000:02:01.0
  DEVBUS=pci
  INTERFACE=eth0
  SEQNUM=827
  PATH=/sbin:/bin:/usr/sbin:/usr/bin
  HOME=/

And an USB-mouse:
  ACTION=add
  SUBSYSTEM=input
  DEVPATH=/class/input/mouse2
  DEVPHYSDEV=/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0
  DEVBUS=usb
  SEQNUM=1001
  PATH=/sbin:/bin:/usr/sbin:/usr/bin
  HOME=/

Hmm, another exception list in wait_for_sysfs killed. :)
Kay


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===== drivers/base/class.c 1.54 vs edited =====
--- 1.54/drivers/base/class.c	2004-10-08 20:32:52 +02:00
+++ edited/drivers/base/class.c	2004-11-04 00:54:26 +01:00
@@ -283,8 +283,33 @@ static int class_hotplug(struct kset *ks
 {
 	struct class_device *class_dev = to_class_dev(kobj);
 	int retval = 0;
+	int i = 0;
+	int length = 0;
 
 	pr_debug("%s - name = %s\n", __FUNCTION__, class_dev->class_id);
+
+	if (class_dev->dev) {
+		/* add physical device backing this class to environment */
+		struct device *dev = class_dev->dev;
+		char *path = kobject_get_path(&dev->kobj, GFP_KERNEL);
+
+		add_hotplug_env_var(envp, num_envp, &i, buffer, buffer_size,
+				    &length, "DEVPHYSDEV=%s", path);
+		kfree(path);
+
+		if (dev->bus)
+			add_hotplug_env_var(envp, num_envp, &i,
+					    buffer, buffer_size, &length,
+					    "DEVBUS=%s", dev->bus->name);
+
+		/* terminate, set to next free slot, shrink available space */
+		envp[i] = NULL;
+		envp = &envp[i];
+		num_envp -= i;
+		buffer = &buffer[length];
+		buffer_size -= length;
+	}
+
 	if (class_dev->class->hotplug) {
 		/* have the bus specific function add its stuff */
 		retval = class_dev->class->hotplug (class_dev, envp, num_envp,