On 11/09/2011 01:28 PM, rohan puri wrote: > > > On Wed, Nov 9, 2011 at 7:22 PM, Alexandru Juncu <alex.juncu@xxxxxxxxxx > <mailto:alex.juncu@xxxxxxxxxx>> wrote: > > On Wed, Nov 9, 2011 at 3:41 PM, Daniel Hilst Selli > <danielhilst@xxxxxxxxx <mailto: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 > > You tried to 'cat' a /dev/my_device file, right? > Was that device file created with the mknod command? > > -- > Alexandru Juncu > > ROSEdu > http://rosedu.org > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx <mailto:Kernelnewbies@xxxxxxxxxxxxxxxxx> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > 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 Thanks Rohan, my fault! _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
