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Re: [vox-tech] Driver Question
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Re: [vox-tech] Driver Question



Thanks Mark,

A textbook (by the same author) I have on networking states this only works
for terminals and sockets, but it's 1992 and things may have changed since
then.....

I'll give it a go and post the results

Thanks again
John W.

----- Original Message -----
From: "Mark K. Kim" <markslist@cbreak.org>
To: <vox-tech@lists.lugod.org>
Sent: Sunday, September 14, 2003 10:47 PM
Subject: Re: [vox-tech] Driver Question


> I think I understood it correctly but I wasn't sure exactly how to do it
> so I was just giving you some pointers.  Anyway, I'm sorta interested in
> this too so I poked around a bit some more.  Looks like the easiest
> technique is to:
>
>    (1) Trap SIGIO signal using signal() system call.
>    (2) fcntl(fd, F_SETFL, O_ASYNC);
>    (3) fcntl(fd, F_SETOWN, getpid());  (might not be necessary)
>    (4) wait for SIGIO signal, handle it in your signal handler.
>
> I haven't tried it.  If it doesn't work, refer to the "fcntl" man page and
> look for any information on asynchronous I/O (grep for "async").  If that
> doesn't work either, try reading section 12.6 in "Advanced Programming in
> the UNIX Environment" by W. Richard Stevens.
>
> BTW, the above technique seems to be a Linux-ism so I'm not sure how it
> will fare on other *NIX.  Stevens explains there are two different
> techniques (one for SVR4 and one for 4.3+BSD), and Linux's technique seem
> like the neither one.  Good luck!
>
> -Mark
>
>
> On Sun, 14 Sep 2003, John Wojnaroski wrote:
>
> > I think I may have mis-stated the problem, my apologies. I'll try
again...
> >
> > In this case the app is a real-time simulation and the hardware provides
a
> > user interface for entering data and a set of switch states. Most of the
> > time the driver will interact with the hardware updating displays,
states,
> > etc. These interrupts never get to the app level, however when the
operator
> > depresses one of any number of push buttons specific data is read into
the
> > driver's kernel space and this data needs to get to the app. So rather
than
> > have the app checking or polling to see if data is available it seems it
> > would be more efficient to issue some signal to an app function to read
the
> > data from kernel to user space. I've been browsing thru the keyboard
drivers
> > and others to try an find an example, no luck so far. In a nutsell, then
> >
> > operator pushes a button, hardware generates an interrupt which launches
> > driver, driver reads data clears interrupt,
> > next, how to notify app that data is available and should be read
> >
> > Thinking some sort of app function that sleeps and is alerted by some
ioctl
> > signal or whatever. How does the keyboard work? Would not this be a
similar
> > implementation?
> >
> > Regards
> > John W
> >
> >
> > ----- Original Message -----
> > From: "Mark K. Kim" <markslist@cbreak.org>
> > To: <vox-tech@lists.lugod.org>
> > Sent: Sunday, September 14, 2003 9:45 PM
> > Subject: Re: [vox-tech] Driver Question
> >
> >
> > > The app is supposed to block ("freeze") if the data hasn't been read
by
> > > the driver.  It stays blocked ("frozen") until the data is available.
> > >
> > > The app can choose to not block in such situation, by using the
"select"
> > > or "poll" system call.  If the file descriptor is set to non-blocking
> > > mode, and if no data is available, then the read() system call
returns -1
> > > and sets "errno" to "EAGAIN".  You probably have to implement these
> > > features into the driver.
> > >
> > > Have fun~!
> > >
> > > -Mark
> > >
> > >
> > > On Sun, 14 Sep 2003, John Wojnaroski wrote:
> > >
> > > > Hi,
> > > >
> > > > Building a driver for a hardware board and things are looking
good...
> > Using
> > > > the O'Reilly book by Rubini and Corbet as a guide, but have a bit of
a
> > > > question??
> > > >
> > > > The driver is interrupt driven when the board posts data to the port
and
> > > > that works fine. Data is retreived and stored in kernel space and
the
> > app
> > > > can use "result = read(fd, mesg, sizeof data)" to access the file (a
> > char
> > > > device). But I can't seem to figure out how to notify the app that
the
> > > > driver has read the data.
> > > >
> > > > Rather than polling would just like to read when data has been
updated (
> > > > kind of like a keyboard using a callback function)
> > > >
> > > > Any thoughts, hints, references would be appreciated.
> > > >
> > > > Thanks
> > > > John W
> > > >
> > > > _______________________________________________
> > > > vox-tech mailing list
> > > > vox-tech@lists.lugod.org
> > > > http://lists.lugod.org/mailman/listinfo/vox-tech
> > > >
> > >
> > > --
> > > Mark K. Kim
> > > http://www.cbreak.org/
> > > PGP key available on the website
> > > PGP key fingerprint: 7324 BACA 53AD E504 A76E  5167 6822 94F0 F298
5DCE
> > >
> > > _______________________________________________
> > > vox-tech mailing list
> > > vox-tech@lists.lugod.org
> > > http://lists.lugod.org/mailman/listinfo/vox-tech
> >
> > _______________________________________________
> > vox-tech mailing list
> > vox-tech@lists.lugod.org
> > http://lists.lugod.org/mailman/listinfo/vox-tech
> >
>
> --
> Mark K. Kim
> http://www.cbreak.org/
> PGP key available on the website
> PGP key fingerprint: 7324 BACA 53AD E504 A76E  5167 6822 94F0 F298 5DCE
>
> _______________________________________________
> vox-tech mailing list
> vox-tech@lists.lugod.org
> http://lists.lugod.org/mailman/listinfo/vox-tech

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