Re: udev and parallel port support

["'Kay Sievers'" <kay.sievers@vrfy.org>]

On Tue, Oct 04, 2005 at 05:14:11PM -0500, Jason Dravet wrote:
> > -----Original Message-----
> > From: Kay Sievers [mailto:kay.sievers@vrfy.org]
> > Sent: Tuesday, October 04, 2005 4:58 PM
> > To: Jason Dravet
> > Cc: 'Greg KH'; linux-hotplug-devel@lists.sourceforge.net
> > Subject: Re: udev and parallel port support
> > 
> > On Tue, Oct 04, 2005 at 04:48:43PM -0500, Jason Dravet wrote:
> > > > -----Original Message-----
> > > > From: Greg KH [mailto:greg@kroah.com]
> > > > Sent: Tuesday, October 04, 2005 4:31 PM
> > > > To: Jason Dravet
> > > > Cc: linux-hotplug-devel@lists.sourceforge.net
> > > > Subject: Re: udev and parallel port support
> > > >
> > > > On Mon, Oct 03, 2005 at 12:24:24PM -0500, Jason Dravet wrote:
> > > > > Hello,
> > > > >
> > > > > I opened bugzilla bug 145148
> > > > > (https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id\x145148) at the
> > > > > beginning of this year.  Udev was creating a bunch of unnecessary
> > items
> > > > in
> > > > > /dev.  The parallel ports were mentioned specifically along with a
> > large
> > > > > number of ttyS and tty nodes.  When redhat responded to the bug I
> > found
> > > > out
> > > > > that udev had to create the parallel port nodes itself using a rule
> > > > because
> > > > > the parallel port module was not loading at boot time.  I opened the
> > bug
> > > > to
> > > > > get the parallel port module to load at boot time so udev could
> > > > dynamically
> > > > > create the nodes instead of creating 4 parallel ports when most
> > people
> > > > have
> > > > > (use) one.
> > > > >
> > > > > I received an email asking me to try the new fedora core 4 kernel.
> > I
> > > > have
> > > > > installed it and it works fine for me.  The issue is udev is still
> > > > creating
> > > > > the parallel port statically instead of dynamically.  When will udev
> > be
> > > > able
> > > > > to dynamically create the nodes for parallel ports?
> > > >
> > > > It does so today just fine, the last time I looked.  It's a kernel
> > > > issue, not a udev issue.
> > > >
> > > > How could udev be creating devices "statically"?  It's up to the
> > kernel
> > > > to export what it has availble, and right now, it just exports them
> > all.
> > > > Is that what bothers you?  If so, feel free to change the kernel code
> > to
> > > > work better if you wish.
> > > >
> > > > But again, it's a kernel issue, not a udev issue.
> > > >
> > > > thanks,
> > > >
> > > > greg k-h
> > >
> > > I am sorry I did not make my self clear.  What I meant is that udev
> > creates
> > > the /dev/lp0, /dev/parport0, /dev/lp1, ..., /dev/parport3 nodes by
> > looking
> > > at /etc/udev/makedev.d/50-udev.nodes instead of actually detecting the
> > > ports.  In the 50-udev.nodes file it says "These device have to be
> > created
> > > manually" and proceeds to list several items include lp0.  At least that
> > is
> > > what happens in version 0.58.  Does it make sense now?
> > 
> > /etc/udev/makedev.d/ exists only on Red Hat. Every distro has it's own
> > way to create the "static" nodes.

> Thank you for the response.  I realize that some devices need static nodes,
> but I am wondering why parallel ports fall into this category at least they
> do according to redhat anyways?

Sure, if you always load the module, there is no need to create the nodes.
In the past opening the node loaded the module, so with the switch to
udev it was just easier just to create the node. :)
Today it should be possible to "coldplug" the module load with the pnp id.

The "raw" parport is in:
  /sys/class/ppdev/parport0

The lp is in:
  /sys/class/printer/lp0

udev creates the nodes for both devices if the module is loaded.

Kay


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