Re: ALSA, snd_intel8x0m and kexec() don't work together(2.6.13-rc3-git4 and 2.6.13-rc3-git3)

From: Eric W. Biederman
Date: Sat Jul 30 2005 - 21:20:17 EST

Lee Revell <rlrevell@xxxxxxxxxxx> writes:

> On Fri, 2005-07-22 at 15:18 +0200, Ralf Hildebrandt wrote:
>> * Denis Vlasenko <vda@xxxxxxxxxxxxx>:
>> > Not happening here on 2.6.12:
>> 2.6.12 didn't have kexec (unless it's a -mm kernel)
>> So how could you boot using kexec then?
> Is kexec supposed to be transparent to all the subsystems, or does ALSA
> have to know how to stop all DMA in order for kexec to work?

It is fairly transparent. device_shutdown on reboot should stop
DMA but that is not kexec specific. kexec may be the only way
the code path is easily tested.

The basic requirement from the kexec side is that the drivers
be able to bring back the device from the state they left it
on reboot.

So in essence it is transparent. But if your driver is not
robust you can have problems.

The fact the new kernel was coming up indicates that kexec
worked but the driver did not successfully initialize,
the hardware from the state it placed it in during shutdown.

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