Device nodes: major, minor numbers

Altera_Forum · ‎01-06-2005

I have been using the Nios II IDE to rebuild and upload my romfs filesystem image to my uKit development board.

I previously did not have a problem communicating via ttyS0.

Now I am having a problem. It gives me an error saying that the device doesn't exist.

Upon checking /dev/ttyS0 and /dev/ttyS1, I am able to see that the minor numbers are all 0 instead of what they should be.

I double checked my filenames under the target directory and it appears that they are OK.

Output from "ls -l dev/*ttyS0*" shown below.

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-rwx------ 1 user mkpasswd 0 Dec 1 14:37 @ttyS0,c,4,64*[/b]

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I even loopback mounted the romfs.bin on a linux system as a romfs and the device files were created properly.

Output from "ls -l dev/ttyS0" shown below.

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crw------- 1 root root 4, 64 Dec 31 1969 ttyS0[/b]

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The problem exists when I try to upload the filesystem to my board. Somehow the device nodes are not being created properly.

Here is the ls -l /dev/ttyS0 output. I noticed that none of my /dev files have their minor number correct. They are all set to zero.

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--- Quote Start ---

crw------- 1 root root 4, 0 Jan 1 1970 ttyS0[/b]

--- Quote End ---

Has anyone else seen this?

Does anyone have a suggestion?

Altera_Forum · ‎01-06-2005

The "ls" command cannot display the minor number correctly. Please use the ls command from busybox, it will tell you the real number.

Altera_Forum · ‎01-06-2005

To fix this bug, the application source ls.c has to be modified. It can be found in application source directory fileutils. The problematic codes start from line 307:

    if (S_ISBLK(statbuf->st_mode) || S_ISCHR(statbuf->st_mode))
                     sprintf(cp, "%3d, %3d ", statbuf->st_rdev >> 8,
                              statbuf->st_rdev & 0xff);

To fix this bug, please change them to

    if (S_ISBLK(statbuf->st_mode) || S_ISCHR(statbuf->st_mode))
                    sprintf(cp, "%3d, %3d ", (unsigned int)(statbuf->st_rdev >> 8),
                             (unsigned int)(statbuf->st_rdev & 0xff));

Altera_Forum · ‎01-07-2005

I will look at recompiling my ls command with the fix.

I have resolved my problem.

I was getting an error indicating that the device didn't exist, so when I did the ls and the minor number wasn't there I assumed that this was the problem.

What I forgot was that I had recently started a new kernel project whereby my nios serial support was not enabled. OOPS.

After recompiling the kernel with serial uart support, the serial port worked properly.

Sadly, it was a dumb mistake with a little deception added in.

Thanks for your help.