Using the /proc filesystem
When adding new hardware to an existing Linux system, you may wish to verify which resources the existing devices are using. The /proc filesystem, the kernel’s status repository, contains this information. The proc files, interrupts, dma, and ioports, show how system resources are currently utilized. (These files may not show devices unless their device files/drivers are open/active. This may make the problem harder to find if you’re experiencing resource conflicts.) The following is an example of /proc/interrupts from a dual-CPU system with an Adaptec dual-AIC7895 SCSI controller:
# cat /proc/interrupts CPU0 CPU1 0: 98663989 0 XT-PIC timer 1: 34698 34858 IO-APIC-edge keyboard 2: 0 0 XT-PIC cascade 5: 7141 7908 IO-APIC-edge MS Sound System 6: 6 7 IO-APIC-edge floppy 8: 18098274 18140354 IO-APIC-edge rtc 10: 3234867 3237313 IO-APIC-level aic7xxx, eth0 11: 36 35 IO-APIC-level aic7xxx 12: 233140 216205 IO-APIC-edge PS/2 Mouse 13: 1 0 XT-PIC fpu 15: 44118 43935 IO-APIC-edge ide1 NMI: 0 ERR: 0
In this example, you can see that interrupt 5 is used for the sound system, so it isn’t available for a second parallel port. The two SCSI controllers are using interrupts 10 and 11, respectively, while the Ethernet controller shares interrupt 10. You may also notice that only one of the two standard IDE interfaces is enabled in the system BIOS, freeing interrupt 14 use for another device.
Here are the /proc/dma and /proc/ioports files from the same system:
# cat /proc/dma ...