On Wed, Nov 9, 2011 at 7:22 PM, Alexandru Juncu <alex.juncu@xxxxxxxxxx> wrote:
On Wed, Nov 9, 2011 at 3:41 PM, Daniel Hilst SelliYou tried to 'cat' a /dev/my_device file, right?
<danielhilst@xxxxxxxxx> wrote:
> I'm trying to create a example char device. The example compiles fine,
> but when I try to "cat" I got "No such device or address". I have
> reviewed the code thousend times and can't see what I'm missing
>
> Here is the code -> http://pastebin.com/Td03U0fK
>
> The read method is not good, I know, but is never called.
>
> I use my own running kenrel to test, I know that is danger. I'm building
> a qemu enviroment to test this better.
>
> Here is uname -a:
> Linux archlinux 3.0-ARCH #1 SMP PREEMPT Fri Oct 7 11:35:34 CEST 2011
> x86_64 Intel(R) Core(TM) i3 CPU M 370 @ 2.40GHz GenuineIntel GNU/Linux
>
> Any idea?
>
> Thanks
Was that device file created with the mknod command?
--
Alexandru Juncu
ROSEdu
http://rosedu.org
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Hello Daniel,
I had the look at the code. The issue is with the cdev_add() call in init_gcdev() function.
int cdev_add(struct cdev *p, dev_t dev, unsigned count) is the prototype
Now the problem was instead of passing second argument of type dev_t you were passing minor number macro.
Fix : - Do following additions : -
1. static int major; // Declare a global major no var.
2. In init_gcdev() after call to alloc_chrdev_region() get major no and store in major var.
major = MAJOR(gcdev->dev);
3. Replace cdev_add() call like this : -
cdev_add(&gcdev->cdev, MKDEV(major, FIRST_MINOR), 1);
Now its running and your read methos is getting called.
Hello Alexandru,
That error was due to improper args passed to cdev_add(). If device file is not present (no mknod done) error would be "No such file or dir"
Regards,
Rohan Puri
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