Hi all,
I have some questions about how to implement extension board usage. My case is on imx8mm-cl-iot-gate. It can add three different types of extension boards. One of the extension boards is SPI extension which have 3 empty slots. And you can add some small boards onto it. One of them is a "TPM2" module. My first question is if I want to use tpm2 in U-boot for measured boot. How to implement this right? Currently I just modify the dts used by U-boot to let it drive the extension board. And let it drive the TPM. But it is not good for upstreaming because when other types of extension boards installed then it is not working. Where to implement this? What is the best practice of this? The second question is about extension manager. I have read the extension.rst. I think I'll implement this anyway because then I can have a command to query what type of extension boards I have. And if the extension board is the 3 slots one. I can then detect which slot is the TPM. I'll implement this anyway because the "extension" command is convenient for users. But it seems to me that it only solves the problem for Linux kernel. It can apply a DTB Overlay to Linux DTB to let Linux knows we have that extension board. But it is too late for U-boot itself, right? The third question is I'm also dong SystemReady IR certificate. That means the dtb for Linux is directly provided by U-boot. We use U-boot dtb directly to Linux kernel. In this case, how to modify that dts dynamically to feed to the Linux kernel by the extension manager? What is the best practice if I want to use U-boot dts for Linux in implementation? Thanks a lot. Yours, Paul
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