By default, PCI devices are supposed to be capable of sharing IRQs. Sharing
should be possible between two PCI devices of same or different types. Also,
a PCI device can be assigned any IRQ and the driver shoule be independent of
the IRQ number. The device drivers should always be designed considering this
issue (unless, a particular device SHOULD NOT share IRQs with other devies due
to some reason).
However, in some OSs, interrupt-sharing of the PCI devices can be configured
(no sharing, sharing with similar devices, sharing with any devices).
BIOS assigns the IRQs of PCI devices depending on the parameters like *type of
PCI device*, *PCI slot* on which the device reside etc. Each BIOS uses its own
algorithm to assign IRQs and hence it might assign same IRQs to two different
PCI devices. There is absolutely no fault of BIOS (or kernel).
However, in some systems, using BIOS setup program, IRQs can be pre-assigned
(or forced) so that no two PCI devices share IRQs.
- Somnath.
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