Tuesday, April 24, 2007

serial line and irq routing

Recently I have got a multi port serial card.
I need it to connect old notebook to pc. Notebook does not have ethernet or usb and I cannot find a pcmcia network card for its old slot in the vicinity. That is why serial line is a solution to setup a tcp/ip network via slip or ppp
The only difficulty was that my pc has only one serial port therefore if it is connected to the net via dial-up serial modem I cannot have neither internet nor just network on my notebook.
So, I've got a serial card and put it in pci slot of my pc. Once I did so I got problem with irqs.
Linux did hang when serial line (even the one on the motherboard) worked for some (short) time. I saw similar things before, on my nubus powermac with unstable kernel and buggy serial driver. That time I remembered Tannenbaum articles about micro kernel advantages.
To solve problem I changed irq settings in bios, disabled m/b serial port, recompiled kernel, tried to put card in other pci slot... and even read serial how-to.
After all I decided to install minix. Yes, it does not have 64 bit port but at least it is a good time and reason to play with it and get experience.
Before reboot and booting minix install cd I noticed interesting line in dmesg (why I didn't notice it earlier?) which suggested to use kernel option pci=routeirq to enable pci interrupts routing on acpi systems. That worked! now I am surfing web and even writing this note :)

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