Re: video mem access with oskit-mach

[Thomas Bushnell, BSG]

Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de> writes:

> MiG doesn't know unsigned short, so I am afraid that I have to use int.
> The conversion from signed shorts to unsigned shorts is implementation
> defined (or can raise a signal even), so I am out of luck here  (unless we
> forbid ports higher than 7fff).

unsigned short is just short with a ctype of "u_short" instead
of "short".  Note <mach/std_types.defs>, which does the following for
32-bit ints:

type int = MACH_MSG_TYPE_INTEGER_32;
type unsigned = MACH_MSG_TYPE_INTEGER_32;

These are, as far as MiG cares, entirely identical; the difference is
the type that gets written in the prototypes for the stubs.

So you can just create

type unsigned16 = MACH_MSG_TYPE_INTEGER_16;

Then you'd have to add unsigned16 to the appropriate .h header.

Or you can do:

type u_short = MACH_MSG_TYPE_INTEGER_16;

And then you are done, because u_short is already in <sys/types.h>.

You could also do:

type unsigned16 = MACH_MSG_TYPE_INTEGER_16 ctype: u_short;

in which case the type has a different name between MiG and C.

> I slowly realize what's involved with kernel side servers.  There
> are quite a few differences.  For example, it seems variable size
> length arguments must be either always in-line (array [*:MAX]) or
> always out-of-line (^array []).  

Yes, I believe this is correct.  It would be nice to extend the
variable version to kernel side servers too, however.