Date: Tue, 15 Mar 2005 15:41:52 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: uber.caulker@gmail.com Cc: freebsd-hackers@freebsd.org Subject: Re: poll or select for ppi? Message-ID: <20050315.154152.25159739.imp@bsdimp.com> In-Reply-To: <5e52cc0005031419056fdf10c6@mail.gmail.com> References: <5e52cc0005031419056fdf10c6@mail.gmail.com>
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In message: <5e52cc0005031419056fdf10c6@mail.gmail.com>
Matt Kory <uber.caulker@gmail.com> writes:
: Is it possible to use poll or select to detect a change in the status
: bits of the parallel port? I tried something like this, and took bits
: 5 and 6 of the status register low and nothing seemed to happen. Is
: what I am trying to do even possible, or I am supposed to take a
: certain bit low to cause a read event? Any help is appreciated.
:
: int ppi_fd;
: char port[] = "/dev/ppi0";
: ppi_fd = open(port, O_RDWR);
:
: fd_set rfds;
: struct timeval tv;
: tv.tv_sec = 0;
: tv.tv_usec = 100000;
:
: while(1) {
: FD_ZERO( &rfds );
: FD_SET( ppi_fd, &rfds );
: if ( select(1, &rfds, NULL, NULL, &tv) ) {
: printf("hi\n");
: }
: }
With the driver, as written: No. You can't poll(2). You can ask the
device often if something has changed yet.
However, it would be relatively simple to add a read channel and poll
support. I've written several custom drivers that do things based on
parallel port interrupts... Such drivers aren't that hard.
Warner
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