Re: serial ports
Magnus Ahltorp (Magnus.Ahltorp@abc.se)
Tue, 6 Aug 1996 01:33:21 +0200 (MET DST)
> This is not a Linux limitation. It is due to the PC architecture. Some
> special "inteligent" cards can achieve this by mean of a special driver.
> Read the Serial-HOWTO, which stands
>
> " The number of serial ports you can use is limited by the number of
> interrupts (IRQ) and port I/O addresses we have to use. This is not a
> Linux limitation, but a limitation of the PC bus. Each serial devices
> must be assigned it's own interrupt and address. A serial device can
> be a serial port, an internal modem, or a multiport serial board.
But this is not true. There must be another reason why Linux' serial
driver doesn't allow multiple ports to use the same IRQ. The serial driver
could very well ask the serial port if it was the one to generate the
interrupt. Don't tell me it's impossible, I have done it myself. Just
check base+2 for a zero in bit 0.
Though, I wouldn't recommend doing so, since it makes the code weird.
/Magnus
magnus@abc.se