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<H2><A NAME="s7">7.</A> <A HREF="Serial-HOWTO.html#toc7">Configuring Overview</A></H2>
<P>In most cases configuring is automatically taken care of and you
have nothing to do. Linux should detect your serial ports, and load
driver modules if needed. Then the driver should insure that IRQ and
address space resources have been allocated. Finally, the application
program which uses the serial port should set the port speed, etc.</P>
<P>For any of this to work, serial support must either be compiled into
the kernel (by you or by whoever compiled your kernel) or provided by
modules that are loaded into the kernel when you start to use the
serial port. In most cases, if it hasn't been compiled into the
kernel, a module(s) will do the job and Linux should hopefully
automatically find and load the correct modules.</P>
<P>But if you have more than 4 (or perhaps 2) serial ports, then the kernel
must be told this as it doesn't seem to do it automatically. See
<A HREF="Serial-HOWTO-15.html#nr_ports">Number of Serial Ports Supported</A>,
<A HREF="Serial-HOWTO-15.html#kernel_conf">Kernel Configuration</A> and.
<A HREF="Serial-HOWTO-15.html#ser_module">Serial Modules</A>.</P>
<P>Once the proper support is in your kernel and modules, then The rest
of the configuring of the serial port should happen automatically.
This is done by the serial driver software often with help from your
application software. But sometimes it doesn't get configured right
and then you need to do it yourself. Or perhaps you need to configure
it in a special way, etc. This HOWTO only covers configuration of the
serial port itself and not the configuring of any devices attached to
the port (such as a modem or printer).</P>
<P>Resource allocation (locating the hardware or low-level configuring)
is assigning each port an IO address, IRQ, and name (such as ttyS2).
This IO-IRQ pair must be set in both the hardware and
become known to the serial driver. We might just call this "io-irq"
configuring for short. The "setserial" program is sometimes used to
tell the driver io-irq info that an administrator has put in a
configuration file or given as parameters to the setserial command.
PnP methods, jumpers, etc, are used to set the IO and IRQ in the
hardware. Details will be supplied later. If you need to configure
but don't understand certain details it's easy to get into trouble.
See
<A HREF="Serial-HOWTO-8.html#locate_port">Locating the Serial Port: IO address IRQs</A>
<A HREF="Serial-HOWTO-11.html#set_serial">What is Setserial</A></P>
<P>The second part (high-level configuring) is assigning it a speed (such
as 115.2k bits/sec), selecting flow control, etc. This is often
initiated by communication programs such as wvdial, PPP, minicom,
picocom or by getty (which you may run on the port so that others may
log into your computer from an old-fashioned dumb terminal connected
to the port). However you will need to tell these programs what speed
you want, etc. by using a menu or a configuration file. This
high-level configuring may also be done manually with the <CODE>stty</CODE>
program. <CODE>stty</CODE> is also useful to view the current status if
you're having problems. See the section
<A HREF="Serial-HOWTO-11.html#stty_">Stty</A></P>
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