Inappropriate ioctl for device

[John Baldwin]

Mohammad Hedayati wrote:
> I'm writing a simple char device. So far everything went so good
> (read/write), but here I'm going to add support for ioctl.
> 
> int
> ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags, struct thread *td)
> {
>      int error = 0;
>      uprintf("Here...\n");
>      return(error);
> }
> and I'm calling it here:
> 
> len = ioctl(cd, 0);
> perror("ioctl");
> 
> but when runnig it says:
> 
> ioctl: Inappropriate ioctl for device
> 
> where's the problem?

0 is not a valid ioctl code.  A valid ioctl code has to have at least 
one of IOC_VOID, IOC_IN, or IOC_OUT set.  Also, if it has either IOC_IN 
or IOC_OUT set, it must have a non-zero size field.  You should use one 
of the _IO* macros from <sys/iocomm.h> to define a valid ioctl code and 
pass that to your driver.

-- 
John Baldwin