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ipmi: Add docs for the IPMI IPMB driver 

Describe how to use the IPMI IPMB driver, including it's quirks.

Signed-off-by: Corey Minyard <minyard@acm.org>
Tested-by: Andrew Manley <andrew.manley@sealingtech.com>
Reviewed-by: Andrew Manley <andrew.manley@sealingtech.com>
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Corey Minyard 2021-09-30 17:07:30 -05:00 committed by Corey Minyard
parent ddf58738f5
commit b81a817af1
1 changed files with 39 additions and 0 deletions
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39
Documentation/driver-api/ipmi.rst
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@ -591,6 +591,45 @@ web page.
The driver supports a hot add and remove of interfaces through the I2C
sysfs interface.
The IPMI IPMB Driver
--------------------
This driver is for supporting a system that sits on an IPMB bus; it
allows the interface to look like a normal IPMI interface. Sending
system interface addressed messages to it will cause the message to go
to the registered BMC on the system (default at IPMI address 0x20).
It also allows you to directly address other MCs on the bus using the
ipmb direct addressing. You can receive commands from other MCs on
the bus and they will be handled through the normal received command
mechanism described above.
Parameters are::
ipmi_ipmb.bmcaddr=<address to use for system interface addresses messages>
ipmi_ipmb.retry_time_ms=<Time between retries on IPMB>
ipmi_ipmb.max_retries=<Number of times to retry a message>
Loading the module will not result in the driver automatcially
starting unless there is device tree information setting it up. If
you want to instantiate one of these by hand, do::
echo ipmi-ipmb <addr> > /sys/class/i2c-dev/i2c-<n>/device/new_device
Note that the address you give here is the I2C address, not the IPMI
address. So if you want your MC address to be 0x60, you put 0x30
here. See the I2C driver info for more details.
Command bridging to other IPMB busses through this interface does not
work. The receive message queue is not implemented, by design. There
is only one receive message queue on a BMC, and that is meant for the
host drivers, not something on the IPMB bus.
A BMC may have multiple IPMB busses, which bus your device sits on
depends on how the system is wired. You can fetch the channels with
"ipmitool channel info <n>" where <n> is the channel, with the
channels being 0-7 and try the IPMB channels.
Other Pieces
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