The Value of Blogging as a programmer

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Today at the local Python meetup, I repeated my little speech encouraging the other members to blog. They, in turn, suggested I write a blog post explaining what I just told them. It is entirely possible I have written this before in my 2.5 decods of recording my thoughts in web format, but maybe I still have something new to add.

When talking about software, esepcially that brand of software that is written for internal consumption at a company, I find it valuable to frame things in terms of “Me. Us. Them.” I might write something for my personal use. Later I dscover other people on my team can use it,too. Finally, I might find that it is worthwhile to make it availble to the larger organization. I think the same might be true about blogging.

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LImiting What an Agent can do

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I do not work with AI tools. This is not advice from experience of working with AI. It is advice from working with access controls in general.

Any agent has responsibility and authority. Responsibility is what it is required to produce. Authority is the set of resources that you provide to that agent. This does not change if the agent is human or automation, and AI agents fall in to that later category.

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Stacking Protocols

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I find myself writing a program in C that is supposed to handle multiple protocols. At its entry point, the protocol is Platform Communication Channel (extended memory, type 3 and type 4). Embedded in that is an Management Component Transport Protocol (MCTP) message, and embedded in that is one of many different protocols.

I might want to swap out the PCC layer in the future for….something else. MCTP can come over many different protocols, so there is a good be that the tool will be more useful if it can assume that the protocol outside of the MCTP layer is something other than MCTP.

One problem I have is that the MCTP header does not have a length field. We do not not know how long the payload is; all it has is version, source, destination, and flags. Thus, if we want to pass a buffer of type MCTP header along, and we want the length, we need to pass it in a separate field. This goes both for incoming (how many bytes to read) and outgoing (how many bytes to write).

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Install a custom Kernel inside a VM

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When debugging Qemu, it might be helpoful to instrument Linux Kernel to see when interrupts get received, or see data on the other side of a transfer. If you have to modify the Kernel on a regular basis, it can be faster to build it in place than to build a customer RPM/DEB and install inside the VM. Here is how I have been going about updating the kernel.

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Viewing the Flattened Device Tree from Qemu

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The Qemu implementation uses a Flattened Device Tree (FTD) to manage the virtual implementation of the physical devices in a machine. I need to create a FTD entry for the MCTP-PCC implementation I am writing in Qemu. Since this is new to me, and I am working (as I most often do) via Ttrial and error, I want to see the FTD entry after I write it. Here is how I am dumping it.

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Debugging Qemu with gdb

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When developing Linux Kernel code, I have found myself wanting to have a test fixture inside the Firmware that lets me inspect the values communicated out of and into the Linux Kernel. I am currently writing one such fixture in Qemu. And I have an interrupt that is not getting handled by the Linux Kernel, I think because it is not getting delivered.

I have found it quite valuable to run this Qemu process in the Gnu Debugger. Here is how I (with help) got to the bottom of the mystery.

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