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Creating device /dev/sonycd with MAKEDEV

Posted on 1997-02-26
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Last Modified: 2013-12-15
Hi,

I found out that the Redhat 4.0 Linux installation had a problem recognizing my CD. So I installed it from my hard drive. After that I tried to get my CD (Sony, type CDU33A) to work, but when I tried to mount my cd, I always get the
error: "....does not recognize cdu31a as a valid block device". Trying to fill in /etc/conf.modules with kernelcfg works (and my kernel is comiled modular), but I still had the same error. Then I checked the /dev/ directory for my device: size of sonycd (and cdu31a) defvices are 0. For the
moment I can access my CD via a line in rc.local:
  /sbin/modprobe cdu31a.o cdu31a_port=0x340 cdu31a_irq=0
and then mounting it (my mount point does exist).
But I want to try the clean way and remaking my device, so I want to use "MAKEDEV sonycd". But this comes bak with the error:
 'device: unknown major number for device cdu31a'
Is this an old version of MAKEDEV? Because I think MAKEDEV makes all devices when installing Linux, and some of those devices are of size 0, which is not very normal.
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Question by:liedekef
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pc012197 earned 50 total points
ID: 1626954
Devices don't have a size at all. What you get when you do "ls -l <device_name>" is the major and minor numbers of the device. Look at /usr/src/linux/Documentation/devices.txt to see which numbers belong to a certain device:

15 char        Joystick
[...]
   block       Sony CDU-31A/CDU-33A CD-ROM
                  0 = /dev/sonycd       Sony CDU-31a CD-ROM

For every major number there is a character device and a block device, with several minor numbers for each.
So, if an 'ls -l /dev/cdu31a' for you looks like this:

brw-------   1 root root 15,   0 Aug 26  1996 /dev/cdu31a

you're fine. You don't need to rerun MAKEDEV. I suppose this is the case, because if you insert the module with modprobe and mount it, it works all right.

Therefore the problem must lie somewhere in the kerneld and conf.modules setup. What does your conf.modules say about your cdrom device? Do you start kerneld before trying to mount the cdrom or after?


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