ATI rage xl.init

Eric W. Biederman ebiederman at
Sun Apr 25 13:29:01 CEST 2004

"Yinghai Lu" <yhlu at> writes:

> 8.
> Sometimes, if you not enable PCI master, the device can not work properly in
> Linux.
> But Eric/Ron didn't enable that in PCI main loop, because some devices don't
> need that.

As a general rule devices don't need that and it is the responsibility
of the device driver to enable/os to enable it.

So the master bit should only be enabled for devices that are needed
to boot.  So we do need to enable this on the ioapic that transmit
interrupts over the pci bus for example.  Both because it is
needed to boot and because it is architectural hardware.

Unless someone can show me a relevant passage of the pci spec,
that says differently.

Any linux device driver that can't cope with a device that does
not have it's bus master bit clear and needs it set is broken.

Devices with bus master set are allowed to DMA into main memory
whenever they feel like it so it is dangerous to enable that
bit indiscriminately.


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