andy baxter wrote: > I just had another look at the onboard firmware config system, and it > does have a page that lets you assign devices labelled A,B,C... to > different physical interrupts, but I'm not sure how to use this properly > or safely. (There's no indication what device 'A' actually is). By > default they are all set to INT 11, which doesn't come up in > /proc/interrupts. The things labeled A, B, ... are the actual hardware interrupts lines that go into your chipset's interrupt controller (in the southbridge). The only mechanism to change which device is connected to which hardware interrupt line is to put the card in some other PCI(e) slot; for onboard devices, this connection is literally hardwired. (Actually, many southbridge chips can use different hardware interrupt lines for the integrated devices, but there is no motherboard maker that allows to reconfigure this in the BIOS.) How these hardware interrupt lines are mapped to interrupt numbers depends on how modern the OS is. First, there are the ISA interrupts 0-15, which were the only interrupts available in the good ol' times of MS-DOS. There are very few ISA interrupts that are not already used by or reserved for ISA devices. The mapping from hardware interrupt line to ISA interrupt is what your BIOS allows you to configure, but this interrupt type isn't used by Linux unless you disable ACPI. Second, there are the new PCI interrupts starting at number 16. These are used when the OS knows how to configure the interrupt controller, which is one of the things done by ACPI. The mapping from hardware interrupt line to interrupt number is fixed, i.e., A=16, B=17, etc. Third, there are message-signaled interrupts (MSIs), which do not use interrupt lines at all and are always unshared. This is the only mechanism to get unshared interrupts for devices that are connected to the same hardware interrupt line. In theory, MSI support is required for all PCI Express devices, but in practice, MSIs are not supported by older Windows versions and by many Windows drivers, so many devices and older chipsets have no or buggy MSI support. However, when MSIs work, they are used by most Linux drivers. Regards, Clemens _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
