From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- Documentation/driver-api/ipmb.rst | 109 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 Documentation/driver-api/ipmb.rst (limited to 'Documentation/driver-api/ipmb.rst') diff --git a/Documentation/driver-api/ipmb.rst b/Documentation/driver-api/ipmb.rst new file mode 100644 index 000000000..209c49e05 --- /dev/null +++ b/Documentation/driver-api/ipmb.rst @@ -0,0 +1,109 @@ +============================== +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 + 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. -- cgit v1.3.1