put "device" symlink into hotplug environment?

put "device" symlink into hotplug environment?

[Kay Sievers]

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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=/

The current patch is only for class-devices block-devices are not covered.

Thanks,
Kay

[-- Attachment #2: kernel-DEVSYSDEV-01.patch --]
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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 00:23:56 +01:00
@@ -283,8 +283,27 @@ 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 */
+		char *dev = kobject_get_path(&class_dev->dev->kobj, GFP_KERNEL);
+
+		add_hotplug_env_var(envp, num_envp, &i, buffer, buffer_size,
+				    &length, "DEVSYSDEV=%s", dev);
+		kfree(dev);
+
+		/* 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,

Re: put "device" symlink into hotplug environment?

[Kay Sievers]

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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


[-- Attachment #2: kernel-DEVSYSDEV-02.patch --]
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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,