Re: Documentation for sysfs, hotplug, and firmware loading.

Cornelia Huck
2007-07-20T07:54:44Z

On Fri, 20 Jul 2007 00:00:01 -0700,
Greg KH <greg@kroah.com> wrote:

> > I don't insist on it, mknod insists on it. You cannot mknod a dev node
> > without specifying block or char.
> >
> > You're saying that sysfs should provide major and minor numbers without
> > anywhere specifying "char" or "block", meaning the major and minor numbers
> > cannot be _used_. I am insisting on getting the third piece of information
> > without which "major" and "minor" are useless.
> >
> > I asked very specifically about this at OLS, several times. What you're
> > telling me now seems to contradict what you told me then.
>
> Here's the rule:
> If the SUBSYSTEM is "block", it's a block device. Otherwise
> it's a char device.

That's actually quite confusing to the casual reader, since:

> But also realize that the majority of events you will get have nothing
> to do with device nodes. I think you are forgetting this fact.

So the rule should be:
If the SUBSYSTEM is "block" (implying major/minor are provided),
it's a block device.
If the SUBSYSTEM is not "block", and major/minor are provided,
it's a char device.
If major/minor are not provided, the event/device is not
relevant to device node creation.