Frequently Asked Questions for FreeBSD 2.X : Serial Communications : How do I configure the kernel for my multiport serial card?
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11.4. How do I configure the kernel for my multiport serial card?

Again, the section on kernel configuration provides information about configuring your kernel. For a multiport serial card, place an sio line for each serial port on the card in the kernel configuration file. But place the irq and vector specifiers on only one of the entries. All of the ports on the card should share one irq. For consistency, use the last serial port to specify the irq. Also, specify the COM_MULTIPORT option.

The following example is for an AST 4-port serial card on irq 7:

            options "COM_MULTIPORT"
            device sio4 at isa? port 0x2a0 tty flags 0x781
            device sio5 at isa? port 0x2a8 tty flags 0x781
            device sio6 at isa? port 0x2b0 tty flags 0x781
            device sio7 at isa? port 0x2b8 tty flags 0x781 irq 7 vector siointr
          
The flags indicate that the master port has minor number 7 (0x700), diagnostics enabled during probe (0x080), and all the ports share an irq (0x001).


Frequently Asked Questions for FreeBSD 2.X : Serial Communications : How do I configure the kernel for my multiport serial card?
Previous: How do I access the serial ports once FreeBSD is running?
Next: I have two multiport serial cards that can share irqs. Can FreeBSD handle this?