答复: ATI rage xl.init
yhlu at tyan.com
Sun Apr 25 15:34:00 CEST 2004
I will double check if current kernel need that for every onboard device.
发件人: Eric W. Biederman [mailto:eric at lnxi.com] 代表 Eric W. Biederman
发送时间: 2004年4月25日 11:47
收件人: Yinghai Lu
抄送: 'Stefan Reinauer'; 'ron minnich'; 'Hendricks David W.'; 'Li-Ta Lo';
主题: Re: ATI rage xl.init
"Yinghai Lu" <yhlu at tyan.com> writes:
> Sometimes, if you not enable PCI master, the device can not work properly
> But Eric/Ron didn't enable that in PCI main loop, because some devices
> 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
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