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<p class="MsoNormal"><span lang="EN-US">Hi:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I check the ipmbd implementation from<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__gerrit.openbmc-2Dproject.xyz_-23_c_openbmc_ipmbbridge_-2B_11130_&d=DwICAg&c=ue8mO8zgC4VZ4q_aNVKt8G9MC01UFDmisvMR1k-EoDM&r=kGibSCEQz-PilnW-r9KNT7_zWJXJNtnSK5aYZCe7SVs&m=9vYrt5dE5uTcGZ0xJvXwlc2qHu9SzkgJbpR7h9W0jXE&s=xLAMWHrLSU8GJiEb4ObBmfmlBhRwK26Z3t4-piFCe1c&e">https://urldefense.proofpoint.com/v2/url?u=https-3A__gerrit.openbmc-2Dproject.xyz_-23_c_openbmc_ipmbbridge_-2B_11130_&d=DwICAg&c=ue8mO8zgC4VZ4q_aNVKt8G9MC01UFDmisvMR1k-EoDM&r=kGibSCEQz-PilnW-r9KNT7_zWJXJNtnSK5aYZCe7SVs&m=9vYrt5dE5uTcGZ0xJvXwlc2qHu9SzkgJbpR7h9W0jXE&s=xLAMWHrLSU8GJiEb4ObBmfmlBhRwK26Z3t4-piFCe1c&e</a>=
and find out that the IPMB request or response messages are passed down to the I2C slave device in the ipmbSend function.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The master device node is /dev/i2c-0 and the slave device node is /sys/bus/i2c/devices/0-1010/slave-mqueue in the ipmbbridge implementation.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The direction is always from the master device to the slave device.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">In normal IPMB usage case, an IPMB request is sent to the master device (say /dev/i2c-3) and then the master device sends that IPMB request to the client device attached to the master device’s bus.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">While an IPMB response returns from the client device, the client device uses an I2C master-write transfer to send the response back to the request originator, which is /dev/i2c-3, according to IPMB spec. So the request
originator becomes an I2C slave at this moment.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">It seems to me that ipmbSend behavior doesn’t get aligned with the description of request/response protocol in IPMB spec.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I might misunderstand the ipmbSend behavior and any comment is welcome.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thank you.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Tyrone<o:p></o:p></span></p>
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