> > What is the maximum size of the buffer that
> > can be passed to ioctl?
> 
> >>From <sys/ioccom.h>:
> 
> /*
>  * Ioctl's have the command encoded in the lower word, and the size of
>  * any in or out parameters in the upper word.  The high 3 bits of the
>  * upper word are used to encode the in/out status of the parameter.
>  */
> #define IOCPARM_MASK    0x1fff          /* parameter length, at most 13 bits */
> 

Is this format for 'request' enforced anywhere in NetBsd, or is
it just a convention?

Every other unix I've met treats the ioctl 'request' and 'argp'
values as token which are passed transparantly to the relevant
device driver.

In a vague attempt to get unique ioctl 'request' values I've
often used 3 characters + a number.

I'm also fairly convinced that 'traditionally' the 'argument'
was prototyped (rather not prototyped, in trad. C) as an 'int'.
However it was often used as a pointer :-)


	David