Hello!
0. I discovered a strange phenomenon with a Debian
Sarge installation. I am able to replicate it
on several machines. It occurs on freshly
installed machines as well as on "older" ones.
The problem is this:
I want to create more than 4000 device files
for a project. I am aware that this is an
uncommon scenario. But it is a customer request.
Generating the device files works well for the
first 255 ones. Then the major number is
incremented by 1 and the minor number starts over
with 0. mknod NEVER returns an error.
1. I tried this with kernel 2.6.8 as well as with
kernel 2.6.16 - no change. devfs is removed.
I can show this phenomenon on a Debian machine
with some example values:
nattest:/home/sperl/tmp# mknod testnode1 c 200 16
nattest:/home/sperl/tmp# mknod testnode2 c 200 255
nattest:/home/sperl/tmp# mknod testnode3 c 200 256
nattest:/home/sperl/tmp# mknod testnode4 c 200 511
nattest:/home/sperl/tmp# mknod testnode5 c 200 512
nattest:/home/sperl/tmp# ls -l
total 0
crw-r--r-- 1 root root 200, 16 2006-11-23 10:07 testnode1
crw-r--r-- 1 root root 200, 255 2006-11-23 10:07 testnode2
crw-r--r-- 1 root root 201, 0 2006-11-23 10:07 testnode3
crw-r--r-- 1 root root 201, 255 2006-11-23 10:07 testnode4
crw-r--r-- 1 root root 202, 0 2006-11-23 10:07 testnode5
2. Doing the same on my Ubuntu installation running a 2.6.15
kernel I get this:
[EMAIL PROTECTED]:/home/sperl/tmp2# mknod testnode1 c 200 16
[EMAIL PROTECTED]:/home/sperl/tmp2# mknod testnode2 c 200 255
[EMAIL PROTECTED]:/home/sperl/tmp2# mknod testnode3 c 200 256
[EMAIL PROTECTED]:/home/sperl/tmp2# mknod testnode4 c 200 511
[EMAIL PROTECTED]:/home/sperl/tmp2# mknod testnode5 c 200 512
[EMAIL PROTECTED]:/home/sperl/tmp2# ls -l
insgesamt 0
crw-r--r-- 1 root root 200, 16 2006-11-23 10:10 testnode1
crw-r--r-- 1 root root 200, 255 2006-11-23 10:11 testnode2
crw-r--r-- 1 root root 200, 256 2006-11-23 10:11 testnode3
crw-r--r-- 1 root root 200, 511 2006-11-23 10:11 testnode4
crw-r--r-- 1 root root 200, 512 2006-11-23 10:11 testnode5
As you can see, on Ubuntu everything is as expected.
3. I even wrote an own version of mknod to check if there is
a bug in the tool. Result: All files are created correctly
with Ubuntu but not with Debian.
4. I wrote a tiny device driver just to verify that the minor
numbers are not only displayed wrong by "ls". Result: I was
able to access all devices with major number 200 from my test
application but not the ones with 201, 202,... For major
number 200 everything looked sane; the minor number I have
seen in my open function looked healthy.
5. When I do create a devicefile like testnode3 (with minor number
256) from the Ubuntu machine via NFS this is what happens:
On the Ubuntu machine the file looks ok (major 200, minor 256).
On the Debian console I see the same file with major 201 and
minor 0.
6. When I start my test application and try to open testnode3 on
the Debian machine I cannot open the device.
7. I already experimented with the kernel configuration. Even
excluding devfs did not help.
I found nothing similair in the Debian bug report database nor
on the rest of the Internet either.
Does anyone of you have an idea?
Thanks for reading!
Greetings,
Stefan
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Stefan Sperling
Network Administration / Software Development
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Gesellschaft für Netzwerk- und Automatisierungstechnologie mbH (N.A.T.)
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