Re: Bus Reset

[Andreas B. <and...@mu...>]

On Sun, Apr 16, 2000 at 09:24:13PM -0700, Jeff Mak wrote:
> Sebastien
> 
> As you are the writer of OHCI driver, I think you are the best one in
> answering my queries:
> 
> I am making use of raw1394 (dev_open) to connect to the other node through
> OHCI kernel driver, when there is a change in power status at PHY of the
> other node, a bus reset would be generated from the hardware.  Is it true
> that the connection in between would be lost?   In other words, can I send
> any other command to the target node using the same handle?

Yes.  You can register a bus reset handler with the libraw handle and
should do so if you need to find out whenever something changes.  I'm
currently working on GUID collection and using that for requests, but
I don't think this applies to your problem.

> The reason why I ask this question is:  I am currently trying  to talk to a
> target node which has a "wake up" feature.   In other words, if the target
> node is idle for period of time, it will try to shutdown itself until it
> receives a "wake up" command from my linux box.   However, when the target
> node is idle and auto shutoff.   Bus reset would be generated causing I
> cannot get the respond from the target node anymore using the same
> raw1394_handle.

If the target has its link layer shut down (I guess it has) it can not
process any requests.  It needs a link-on phy packet.  Sending phy
packets is not implemented yet.

>   I have tried to deactivate the bus reset event on
> interrupt of OHCI driver but it is not working.   I believe deactivating the
> interrupt event mask on bus reset is just ignore the bus reset on kernel
> driver side.

Ignoring a bus reset can only cause harm and will not help you there.

> I suppose if the target node get the power from the firewire bus  and my
> firewire card is a power supplier, there shouldn't be any bus reset even if
> the target node is in power off mode.   Is my understanding correct?    I
> know that this is IEEE1394 specific and if you have any suggestion, please
> let me know.

A bus reset is created whenever a node is added, removed, powered up
or powered down.  Anything that would change SelfID information, in
short.

-- 
 Andreas E. Bombe <and...@mu...>    DSA key 0x04880A44
http://home.pages.de/~andreas.bombe/    http://linux1394.sourceforge.net/