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Altera_Forum's avatar
Altera_Forum
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21 years ago

Device nodes: major, minor numbers

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.

<div class='quotetop'>QUOTE </div>

--- Quote Start ---

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

--- Quote End ---

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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--- Quote Start ---

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

--- Quote End ---

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.

<div class='quotetop'>QUOTE </div>

--- 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?

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    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&#39;t exist, so when I did the ls and the minor number wasn&#39;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.