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

[Anand Babu Periasamy]

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

Hi Matt,
If you use SMS_ATN flag, then you should also call "Get Message Flags" and check if 
"Receive Message Available" flag is set. SMS_ATN flag can also be set for other reasons 
such as watchdog pre-timeout, event message buffer full and OEM events.

My understanding was to use OBF flag for this purpose.

Check this out: Figure 9-7, KCS Interface BMC to SMS Read Transfer Flow Chart
http://download.intel.com/design/servers/ipmi/IPMI2_0E4_Markup_061209.pdf

SMS_ATN seems logical for this purpose given its name, but IPMI Spec uses OBF in its data 
flow diagram. SMS_ATN and OBF both seems to do the same job, except OBF is simple.
When should we check for SMS_ATN over OBF or should we check both always? Even OpenIPMI 
KCS driver uses OBF and not SMS_ATN flag for reading from registers.

SMS_ATN seems useful for high level polling (watch dog daemon). If all system management 
interfaces supports this flag, then it is worth exposing generic bmc_check_idle() api.

Your patches are most welcome.

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Anand Babu Periasamy
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