support for mctp over smbus in backport driver

[umairsiddiqui-digitek]

According to n6001 bmc user guide, in addition to

sudo fpgainfo bmc

the bmc cpld of n6001 supports other methods for telemetry reading:

...

With previous ofs release ofs-2024.1-6.1-2, there was mctp-i2c.c driver

https://github.com/OFS/linux-dfl/blob/ofs-2024.1-6.1-2/drivers/net/mctp/mctp-i2c.c

and can be enabled by CONFIG_MCTP=y

but in current ofs-2024.2-1 this driver mctp-i2c.c is missing.

[pcolberg]

Thanks @umairsiddiqui-digitek for pointing this out.

The mctp-i2c driver was added in Linux 5.17 and does not depend on the DFL framework. As such it is most likely out of scope for the Linux DFL backport driver, which purpose is to bridge the gap between downstream DFL driver development and upstreaming to the Linux kernel. The fact that the full-tree DFL kernel supplied this driver is a side effect of the kernel version it was based on.

Which distribution and kernel version are you using? The RHEL 9 kernel is based on Linux 5.14 which does not yet contain the driver, and neither does the RHEL kernel contain a backport. For Ubuntu 22.04 LTS, the 6.5 (HWE) and 6.8 (HWE) kernels provide the driver. As a feasible work-around for any distribution, you could build, e.g., your own upstream Linux 6.6.* (LTS) kernel and build the Linux DFL backport driver against it for the latest DFL drivers.

[umairsiddiqui-digitek]

In previous OFS releases I used the recommended tag of linux-dfl kernel 6.1.78 over default RHEL 8.9 (kernel 4.18.0-513.5.1.el8_9) . For current release I use RHEL 8.10 (4.18.0-553.el8_10) with backport driver.