Re: pass-through linux ioctl for mfi(4)

[David Holland <dholland-tech%netbsd.org@localhost>]

On Tue, Sep 18, 2012 at 02:01:25AM +0700, Robert Elz wrote:
 >   | Sorry but I can't see how a kernel with COMPAT_LINUX but without
 >   | mfi would compile.
 > 
 > The way I proposed it, it wouldn't, but given that we have control
 > of the mfi driver, we can do "interesting stuff" to its cdevsw.
 > 
 > As a storage device driver (that's what it is, right?) it wouldn't
 > normally have a d_tty, so you could give it one, and fill the
 > struct tty with identifying info (values that would make no sense
 > for a real tty device), and then test that instead.
 > 
 > eg; Its t_dev field could be absurd, its t_oproc could be set to
 > the same value as the d_stop in cdevsw (safe to call as long as the
 > 2nd arg that d_stop is called with is ignored) and more...

Hacks like this have a short shelf life, so let's not...

 > In any case, there are certainly things that can be done to allow you
 > to directly test whether the driver you're using is a particular one
 > without building in knowledge of device numbers.
 > 
 > Even better might be to extend cdevsw with a field that gives the
 > driver name, that would probably be useful in all kinds of places.

Yes.

-- 
David A. Holland
dholland%netbsd.org@localhost