Re: [linux-usb-devel] Re: usb sysfs intf files no longer createdwhen probe fails

From: Stelian Pop
Date: Wed Jun 22 2005 - 11:03:20 EST

Le mercredi 22 juin 2005 Ã 11:41 -0400, Alan Stern a Ãcrit :

> This is a curious aspect of the driver model core. Should failure of a
> driver to bind be considered serious enough to cause device_add to fail?
> The current answer is Yes unless the driver's probe routine returns
> -ENODEV or -ENXIO, in which case the failure is not considered serious.

Indeed. I've also tracked my problem down to the hid core which returns
-EIO when it fails to drive an unknown HID device, instead of a more
logical -ENODEV (this is not a failure to init a known device, but
rather the impossibility to init an unknown device).

The patch below solves the problem for me:

Index: linux-2.6-trunk.git/drivers/usb/input/hid-core.c
--- linux-2.6-trunk.git.orig/drivers/usb/input/hid-core.c 2005-06-22
10:33:23.000000000 +0200
+++ linux-2.6-trunk.git/drivers/usb/input/hid-core.c 2005-06-22
17:43:10.000000000 +0200
@@ -1784,7 +1784,7 @@
if (!hid->claimed) {
printk ("HID device not claimed by input or hiddev\n");
- return -EIO;
+ return -ENODEV;


> IMO this is a perverse way of doing things. The existence of a device has
> nothing to do with what driver is bound to it. Either the device exists
> or it doesn't -- and if it exists, failure to bind a driver shouldn't
> prevent adding the device into sysfs. Right now, however, it does.

I agree, presence in /sys/devices shouldn't be related to the existence
or success/failure of a driver. The link between /sys/class
towards /sys/devices is already saying this.

Stelian Pop <stelian@xxxxxxxxxx>

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