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SubjectRe: [PATCH] Added devfs support for i386 msr/cpuid driver
On Mon, 27 Aug 2001, Richard Gooch wrote:

> 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.

I actually pondered a while on this, and settled on
the cut'n'paste-from-mtrr.c version. There is no error
check there, and I just overlooked it.

The defence for the #ifdefs is that I didn't see
register_chrdev() being aware of devfs, and I thought
we'd be better off just not calling register_chrdev()
at all if we have devfs.

It's not like I personally like #ifdefs, but it seemed
justified to my inexperienced eyes at that point. And
there's a #ifdef CONFIG_DEVFS_FS around the call in
mtrr.c too, and I thought it safe to do like what's
already in the official tree.

In microcode.c however, is the new-style without #ifdef
(or rather with the #ifdef in the headers instead)
and with error checking, but microcode_init() doesn't
use register_chrdev() anyway, even if devfs is not
supported.

Please enlighten me!

> Regards,
>
> Richard....


Grateful for comments,


Per


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