Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 31 May 1999 00:14:35 -0400 (EDT) | From | "Theodore Y. Ts'o" <> | Subject | Re: Hard coding default COM3/4 IRQ. |
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Date: Fri, 28 May 1999 13:54:06 -0400 (EDT) From: "Mike A. Harris" <mharris@ican.net>
Could someone please let me know how to change the _DEFAULT_ COM3 and COM4 IRQ for the linux kernel? I could probably find it easily enough by hunting through the source, but if someone could just let me know it would be a bit easier.
You can do it by editing the table in include/asm/serial.h
Also, it would be nice if this were a CONFIG option. Now I know it is easily rectified in userland by using the setserial program, and that is how I do it, however with various new installations out there, I often forget to configure the com IRQ, and as such the modem wont work.
Put an rc.serial into /etc/rc.d, and that way you don't have to remember....
Also, why doesn't Linux automatically configure the IRQ on the COM port? I'm not complaining, however every single installation of Windows 95 I've seen yet, has miraculously and transparently configured the COM IRQ. This leads me to believe that there is a safe and consistent way of determining what IRQ a given COM port has.
Is there any technical reason for not autoprobing serial IRQ's? Does a kernel patch to do this exist? Does any of this sound like it might be possible to throw into 2.2.x? What about 2.3.x?
There is a CONFIG option for doing autodetection of the IRQ, CONFIG_SERIAL_SHARE_IRQ; you need to answer yes to CONFIG_SERIAL_EXTENDED to see the extra serial config options. The problem is that it doesn't always work. I suspect that Linux folk very often have a lot more random hardware attached to their machines than Windows folks, and these random ISA bus cards can confuse an autodetection algorithm.
It works *most* of the time, but even when it fails 0.001% of the time, if 10% of the people for whom it fails sends me mail, with a 7-10 million user base, that's still a lot of e-mail, and basically, I got tired of trying to support it. That's why it's off by default, and the config option is labeled "unsafe", since sometimes the autodetection can screw up other devices in your systems who really are supposed to have that irq.
- Ted
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