Re: [RFC PATCH] convert uhci-hcd to use debugfs

[Josh Boyer <jdub@us.ibm.com>]

On Fri, 2004-12-10 at 09:27, Greg KH wrote:
> 
> > > -#ifdef CONFIG_PROC_FS
> > > -	ent = create_proc_entry(hcd->self.bus_name, S_IFREG|S_IRUGO|S_IWUSR, uhci_proc_root);
> > > -	if (!ent) {
> > > -		dev_err(uhci_dev(uhci), "couldn't create uhci proc entry\n");
> > > +	dentry = debugfs_create_file(hcd->self.bus_name, S_IFREG|S_IRUGO|S_IWUSR, uhci_debugfs_root, uhci, &uhci_proc_operations);
> > > +	if (!dentry) {
> > 
> > That won't work if debugfs is not configured.  You'll get back (void *)
> > -ENODEV, which is not NULL.
> 
> That's exactly correct.  We do _not_ want NULL to be returned if debugfs
> is not configured in.  We want to be able to detect if an error
> happened, not if the feature was just not configured.  Otherwise, if we
> did return NULL if debugfs was not enabled, this code would just fail
> and the uhci startup would never happen.
> 
> This is why people have to wrap proc functions in #ifdef, and why no one
> ever checks the return values from devfs calls.  It's a real problem and
> I don't want to duplicate that again.

Ah, ok I see now.  Good point.  I should have looked at the code instead
of just trying to infer everything from the patch ;).

josh