[plug] Device files

[Mark O'Shea]

On Wed, 2005-03-30 at 23:28 +0800, Jim Householder wrote:
> Hi
> 
> How is the correspondence between device files in /dev and hardware
> determined and/or coded?
> 
> I want to use a parallel port to control a small LCD character display
> and some relays.  I have installed parapin
> (http://parapin.sourceforge.net) with no errors.
> 
> I have a separate parallel port card installed which I want to use.
> Having burned my fingers in the past, I *really* don't want to
> use the port on the motherboard.
> 
> The parapin program appears to execute ok, but I see nothing.  I
> suspect the driver defaults to the port I don't want to use.
> 
> The script I run to create /dev/parport has the following:
> NAME="parport"
> depmod
> modprobe kparapin
> modprobe parapindriver devname=${NAME}
> rm -f /dev/${NAME}
> mknod /dev/${NAME} u `grep $NAME /proc/devices | cut -d " " -f 1` 0
> 
> /proc/devices appears empty (length 0, file says it's empty), yet
> ls -al /dev/parport gives
> crwxrwxrwx  1  root root  253, 0  Mar 30 22:15 2005  parport
> 
> Where did the 253 major come from?
> How can I create a file that points to the PCI card?
> I get the following numbers according to XP:
> PCI
> Bus            0
> Device         7
> Sub-device    16
> Function       0
> 
> TIA
> Jim
Hi Jim,

It looks like you need to edit the $NAME to set it to the correct
parallel port.  See:
dmesg|grep par
for the one you want.

try using cat to see the contents of /proc/devices this will tell you
where it got that major from.  Remember that /proc is not a real
filesystem, most of it's contents have 0 length, but they are not empty.

Regards,
-- 
Mark O'Shea