On 8 Feb 2002, Kin Cho wrote:

> Bill Studenmund <wrstuden@netbsd.org> writes:
>
> > 	cnopen(<console dev for your port>, FREAD | FWRITE | <other opts>
> > 		0, curproc);
>
> What can I use for <console dev for your port>?  I tried using
> cn_tab->cn_dev but that's forbidden in cnopen because cn_dev is
> alrady set to our "com0" device in com_attach_subr in
> com.c:
>
> 		cn_tab->cn_dev = makedev(maj, sc->sc_dev.dv_unit);

ls -l /dev/console

For i386, it's major 0, minor 0. So "0" is the right value.

> > /*
> >  * Set up a uio to do a read, then call cnread()
> >  */
>
> I have no experience with uio.  Searching around, here's what I
> come up with:
>
>             struct iovec aiov;
>             struct uio auio;
>             int buf[2];			// code and lsr as stored in comintr?
>             aiov.iov_base = buf;
>             aiov.iov_len = sizeof(buf);
>             auio.uio_iov = &aiov;
>             auio.uio_iovcnt = 1;
>             auio.uio_offset = 0;
>             auio.uio_resid = 0;
>             auio.uio_segflg = UIO_SYSSPACE;
>             auio.uio_rw = UIO_READ;
>             auio.uio_procp = curproc;
> 	    ret = cnread(<dev>, &auio, 0);
>
> I doubt that iov_len, uio_offset, and uio_resid are right.
> Any suggestion what they should be?

man read tells some.

uio_offset is fine, as you're reading a device that can't seek. uio_resid
is how much is left to do, 0 is a good initial value.

iov_len is the length of the memory area pointed to by iov_base. i.e. the
size of the buffer.

Note that you will be reading characters just like a userland process
would. So the standard tty processing will have happened.

Take care,

Bill