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Re: [Freeipmi-devel] KCS Driver & SMS_ATN Register

From: Matt Jerdonek
Subject: Re: [Freeipmi-devel] KCS Driver & SMS_ATN Register
Date: Thu, 18 Feb 2010 13:24:26 -0800 (PST)

Al & Anand,

Thanks for the quick response.  I'm planning on using libfreeipmi to create a custom application that, among other things, will have to read event flags from the local event log and query sensors on local and remote BMCs.

I looked at the spec, and I think I have a slightly different understanding (I'm not saying I'm right -- I may be misunderstanding the spec).  I don't think SMS_ATN and OBF can be used interchangeably.  Here's my understanding:
1) If the SMS_ATN bit is set the local BMC requires some attention.
2) A GET MESSAGE FLAGS command should be sent to query the BMC.
3) If bit 0 is set in the response, that indicates a receive message is available.  From looking at the ipmi_kcs_cmd_api_ipmb code, it appears as if that code polls the local BMC with GET MESSAGE cmds instead of using this bit to indicate when the response from the remote BMC is ready.  While polling may not be ideal, it's certainly ok for my application.
4) If bit 1 is set in the response, that indicates an event is available.
5) I'll ignore the pre-watchdog timeout and OEM bits for now ...

I don't understand how libfreeipmi notifies the application that an event is available without monitoring the SMS_ATN bit.  I think I want to create a patch that does the following:
1) Creates a callback from libfreeapi to the application when an event occurs.
2) Monitors the SMS_ATN bit.
3) If set, invokes the callback.

The application would be responsible for issuing the GET MESSAGE FLAGS command and handling the response.  One downside of this approach is that it prevents you from ever making ipmi_kcs_cmd_api_ipmb event-driven.  What do you two think?


From: Al Chu <address@hidden>
To: Matt Jerdonek <address@hidden>
Cc: address@hidden
Sent: Thu, February 18, 2010 10:58:06 AM
Subject: Re: [Freeipmi-devel] KCS Driver & SMS_ATN Register

Hi Matt,

Definitely open to patches.  Looking over the IPMI spec, I agree w/
A.B., it seems to be more useful for a higher level monitoring, w/ the
Get Message Flags and similar commands.  I can think of several patch

1) add a KCS driver flag for checking for SMS_ATN in addition to OBF (or
instead of??).  Flags may be propogated up into higher level APIs too.

2) an additional function that checks for SMS_ATN in addition/or instead
of OBF that users can call instead.

It would be useful to understand your use case too.  Are you using the
KCS driver and IPMI bridging commands to bridge from one BMC to another



On Wed, 2010-02-17 at 18:51 -0800, Matt Jerdonek wrote:
> Hello,
> The KCS driver appears to not use the SMS_ATN register.  This register
> is useful for BMC-to-BMC communication to know when the remote BMC has
> responded.  Are there any plans to monitor this register in future
> releases?  If not, are the maintainers open to including a patch?
> Thanks,
> -Matt
> _______________________________________________
> Freeipmi-devel mailing list
> address@hidden
> http://*
Albert Chu
Computer Scientist
High Performance Systems Division
Lawrence Livermore National Laboratory

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