Re: [PATCH] Added devfs support for i386 msr/cpuid driver

[Richard Gooch <rgooch@ras.ucalgary.ca>]

Arjan van de Ven writes:
> > 
> >  int __init msr_init(void)
> >  {
> > +#ifdef CONFIG_DEVFS_FS
> > +    devfs_handle = devfs_register(NULL, "cpu/msr", DEVFS_FL_DEFAULT, 0, 0,
> > +                                  S_IFREG | S_IRUGO | S_IWUSR,
> > +                                  &msr_fops, NULL);
> > +#else
> >    if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
> >      printk(KERN_ERR "msr: unable to get major %d for msr\n",
> >            MSR_MAJOR);
> >      return -EBUSY;
> >    }
> > +#endif
> 
> this must be wrong as you don't check for devfs_register failures...

The reason it's wrong is because he put #ifdef's in there. The
functions should just be called unconditionally. The #ifdef's are in
the header.

> Also why devfs can't just use register_chrdev and not touch ALL
> drivers is beyond me, but it has been like that for a while now...

Huh?!? I thought that should be obvious. Think about it,
register_chrdev() registers a *major*, whereas devfs_register()
registers an individual device node. The former has no way of
representing which devices are detected, the latter sets up a 1:1
relationship between devices and device nodes (which is what people
actually want).

				Regards,

					Richard....
Permanent: rgooch@atnf.csiro.au
Current:   rgooch@ras.ucalgary.ca