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authorKees Cook <kees+treewide@kernel.org>2026-09-02 15:31:14 -0700
committerKees Cook <kees@kernel.org>2026-09-04 21:37:00 -0700
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treec65086f9bdcd48c6360fb7cb4598bca084da1f32 /Documentation/driver-api/ipmb.rst
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treewide: refresh kmalloc_obj() conversionsgrafted
This is another run of the Coccinelle script for converting kmalloc() family of allocations to kmalloc_obj() via the existing rules in scripts/coccinelle/api/kmalloc_objs.cocci This catches both the set of kmalloc() uses added since the first kmalloc_obj() conversions in v7.0 and adds a large group missed in the first pass due to Coccinelle not interacting well with the cleanup.h scoped_...() family of macros[1]. I worked around this with spatch's "--macro-file" argument to a file with all the scoped_...() macros mapped to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control flow indicator I could find. Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc, riscv, and s390 with no new warnings. Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1] Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2] Signed-off-by: Kees Cook <kees+treewide@kernel.org>
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+==============================
+IPMB Driver for a Satellite MC
+==============================
+
+The Intelligent Platform Management Bus or IPMB, is an
+I2C bus that provides a standardized interconnection between
+different boards within a chassis. This interconnection is
+between the baseboard management (BMC) and chassis electronics.
+IPMB is also associated with the messaging protocol through the
+IPMB bus.
+
+The devices using the IPMB are usually management
+controllers that perform management functions such as servicing
+the front panel interface, monitoring the baseboard,
+hot-swapping disk drivers in the system chassis, etc...
+
+When an IPMB is implemented in the system, the BMC serves as
+a controller to give system software access to the IPMB. The BMC
+sends IPMI requests to a device (usually a Satellite Management
+Controller or Satellite MC) via IPMB and the device
+sends a response back to the BMC.
+
+For more information on IPMB and the format of an IPMB message,
+refer to the IPMB and IPMI specifications.
+
+IPMB driver for Satellite MC
+----------------------------
+
+ipmb-dev-int - This is the driver needed on a Satellite MC to
+receive IPMB messages from a BMC and send a response back.
+This driver works with the I2C driver and a userspace
+program such as OpenIPMI:
+
+1) It is an I2C slave backend driver. So, it defines a callback
+ function to set the Satellite MC as an I2C slave.
+ This callback function handles the received IPMI requests.
+
+2) It defines the read and write functions to enable a user
+ space program (such as OpenIPMI) to communicate with the kernel.
+
+
+Load the IPMB driver
+--------------------
+
+The driver needs to be loaded at boot time or manually first.
+First, make sure you have the following in your config file:
+CONFIG_IPMB_DEVICE_INTERFACE=y
+
+1) If you want the driver to be loaded at boot time:
+
+a) Add this entry to your ACPI table, under the appropriate SMBus::
+
+ Device (SMB0) // Example SMBus host controller
+ {
+ Name (_HID, "<Vendor-Specific HID>") // Vendor-Specific HID
+ Name (_UID, 0) // Unique ID of particular host controller
+ :
+ :
+ Device (IPMB)
+ {
+ Name (_HID, "IPMB0001") // IPMB device interface
+ Name (_UID, 0) // Unique device identifier
+ }
+ }
+
+b) Example for device tree::
+
+ &i2c2 {
+ status = "okay";
+
+ ipmb@10 {
+ compatible = "ipmb-dev";
+ reg = <0x10>;
+ i2c-protocol;
+ };
+ };
+
+If xmit of data to be done using raw i2c block vs smbus
+then "i2c-protocol" needs to be defined as above.
+
+2) Manually from Linux::
+
+ modprobe ipmb-dev-int
+
+
+Instantiate the device
+----------------------
+
+After loading the driver, you can instantiate the device as
+described in 'Documentation/i2c/instantiating-devices.rst'.
+If you have multiple BMCs, each connected to your Satellite MC via
+a different I2C bus, you can instantiate a device for each of
+those BMCs.
+
+The name of the instantiated device contains the I2C bus number
+associated with it as follows::
+
+ BMC1 ------ IPMB/I2C bus 1 ---------| /dev/ipmb-1
+ Satellite MC
+ BMC1 ------ IPMB/I2C bus 2 ---------| /dev/ipmb-2
+
+For instance, you can instantiate the ipmb-dev-int device from
+user space at the 7 bit address 0x10 on bus 2::
+
+ # echo ipmb-dev 0x1010 > /sys/bus/i2c/devices/i2c-2/new_device
+
+This will create the device file /dev/ipmb-2, which can be accessed
+by the user space program. The device needs to be instantiated
+before running the user space program.