Re: [PATCH] add transport class symlink to device object

[Greg KH]

On Wed, Aug 17, 2005 at 10:23:11PM -0700, Greg KH wrote:
> On Mon, Aug 15, 2005 at 05:41:17PM -0500, James Bottomley wrote:
> > Actually, isn't the fix to all of this to combine Greg and James'
> > patches?
> 
> Yes it is.
> 
> > The Greg one fails in SCSI because we don't have unique class device
> > names (by convention we use the same name as the device bus_id) and
> > James' one fails for ttys because the class name isn't unique.  However,
> > if the link were derived from something like
> > 
> > <class name>:<class device name>
> > 
> > Then is would be unique in both cases.
> 
> I agree.
> 
> > Unless anyone can think of any more failing cases?
> 
> I'll try this out and see if anything breaks :)

Ok, here's the patch.  I like it, and I think it will prevent any
duplicate symlinks from happening.  Anyone have any objections?

thanks,

greg k-h

--------------

Driver core: link device and all class devices derived from it.

To ease the task of locating class devices derived from a certain
device create symlinks from parent device to its class devices.
Change USB host class device name from usbX to usb_hostX to avoid
conflict when creating aforementioned links.

Tweaked by Greg to have the symlink be "class_name:class_device_name"
in order to prevent duplicate links.

Signed-off-by: Dmitry Torokhov <dtor@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/base/class.c   |   33 +++++++++++++++++++++++++++++++--
 drivers/usb/core/hcd.c |    2 +-
 2 files changed, 32 insertions(+), 3 deletions(-)

--- gregkh-2.6.orig/drivers/base/class.c	2005-08-17 23:27:02.000000000 -0700
+++ gregkh-2.6/drivers/base/class.c	2005-08-17 23:27:25.000000000 -0700
@@ -452,10 +452,29 @@ void class_device_initialize(struct clas
 	INIT_LIST_HEAD(&class_dev->node);
 }
 
+static char *make_class_name(struct class_device *class_dev)
+{
+	char *name;
+	int size;
+
+	size = strlen(class_dev->class->name) +
+		strlen(kobject_name(&class_dev->kobj)) + 2;
+
+	name = kmalloc(size, GFP_KERNEL);
+	if (!name)
+		return ERR_PTR(-ENOMEM);
+
+	strcpy(name, class_dev->class->name);
+	strcat(name, ":");
+	strcat(name, kobject_name(&class_dev->kobj));
+	return name;
+}
+
 int class_device_add(struct class_device *class_dev)
 {
 	struct class * parent = NULL;
 	struct class_interface * class_intf;
+	char *class_name = NULL;
 	int error;
 
 	class_dev = class_device_get(class_dev);
@@ -500,9 +519,13 @@ int class_device_add(struct class_device
 	}
 
 	class_device_add_attrs(class_dev);
-	if (class_dev->dev)
+	if (class_dev->dev) {
+		class_name = make_class_name(class_dev);
 		sysfs_create_link(&class_dev->kobj,
 				  &class_dev->dev->kobj, "device");
+		sysfs_create_link(&class_dev->dev->kobj, &class_dev->kobj,
+				  class_name);
+	}
 
 	/* notify any interfaces this device is now here */
 	if (parent) {
@@ -519,6 +542,7 @@ int class_device_add(struct class_device
 	if (error && parent)
 		class_put(parent);
 	class_device_put(class_dev);
+	kfree(class_name);
 	return error;
 }
 
@@ -584,6 +608,7 @@ void class_device_del(struct class_devic
 {
 	struct class * parent = class_dev->class;
 	struct class_interface * class_intf;
+	char *class_name = NULL;
 
 	if (parent) {
 		down(&parent->sem);
@@ -594,8 +619,11 @@ void class_device_del(struct class_devic
 		up(&parent->sem);
 	}
 
-	if (class_dev->dev)
+	if (class_dev->dev) {
+		class_name = make_class_name(class_dev);
 		sysfs_remove_link(&class_dev->kobj, "device");
+		sysfs_remove_link(&class_dev->dev->kobj, class_name);
+	}
 	if (class_dev->devt_attr)
 		class_device_remove_file(class_dev, class_dev->devt_attr);
 	class_device_remove_attrs(class_dev);
@@ -605,6 +633,7 @@ void class_device_del(struct class_devic
 
 	if (parent)
 		class_put(parent);
+	kfree(class_name);
 }
 
 void class_device_unregister(struct class_device *class_dev)
--- gregkh-2.6.orig/drivers/usb/core/hcd.c	2005-08-17 23:26:55.000000000 -0700
+++ gregkh-2.6/drivers/usb/core/hcd.c	2005-08-17 23:27:04.000000000 -0700
@@ -782,7 +782,7 @@ static int usb_register_bus(struct usb_b
 		return -E2BIG;
 	}
 
-	bus->class_dev = class_device_create(usb_host_class, MKDEV(0,0), bus->controller, "usb%d", busnum);
+	bus->class_dev = class_device_create(usb_host_class, MKDEV(0,0), bus->controller, "usb_host%d", busnum);
 	if (IS_ERR(bus->class_dev)) {
 		clear_bit(busnum, busmap.busmap);
 		up(&usb_bus_list_lock);
-
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