Re: Lazy Newbie Question

[Calin A. Culianu]

On Tue, 21 May 2002, Calin A. Culianu wrote:

> On 21 May 2002, Kevin Buhr wrote:
>
> > Well, as you can see from the implementation of "comedi_open" that's
> > right in front of you, that code doesn't do anything with the filename
> > except parse it as string of the form "/dev/comediNNN" to get the
> > minor number "NNN".  It looks like a cheesy hack to fake the
> > kernel-mode interface to look like the user-mode interface, but that's
> > all it is.  So, as Richard said, we still haven't seen any evidence
> > that Comedi requires manipulating files in kernel space.
> >
> > It's quite strange how rude and evasive you're being when everyone
> > who's replied has been polite and helpful.  Perhaps if you lost the
> > attitude and told us what it is you're really trying to do, we could
> > help you more effectively.
> >
> > I mean, either we're all too dim to understand your device driver
> > hacking skills, in which case there's no point in you wasting your
> > time here, or one of us has enough of a clue to help, in which case
> > we'd all benefit from you explaining your problem as fully as you are
> > able instead of demanding we show you how to do the impossible (i.e.,
> > stat a file without a process context).

I have a process context.  This will be happening from module_init() in a
module I am writing, which, last I checked, uses the process context of
the process that did the system call.

>
>
>
> > By the way, in case you missed it---and it seems you did---Richard
> > already gave you the right answer in the message you mistakenly
> > dismissed as a flame.  If you really need to stat a file from the
> > kernel, you do this with a helper process in the form of a bona fide
> > user process or a kernel thread.  Because this is relatively
> > complicated to get right (there's a damn good reason the code in
> > "comedi_open" just fakes it), you don't want to do this unless you
> > have to.
>

No, I understood what Richard was saying, but he was being kind of rude
and lecturing.  He could have been just factual, sans attitude.

Anyway, if you honestly want to help me, then please enlighten me,
otherwise spare me the lectures.

And the thing that comedi does with /dev/comeiXX is a cheap hack that I
wanted to do away with, which was *why* I was going to try and figure out
the ACTUAL device minor on a vfs character device, in order to fool
comedi_open().

-Calin