Power-Management on tsvinc

HTC Desire Z battery tile: the SD card its launcher can't write

Sun, 11 Jan 2026 00:00:00 +0000

The first builds of the logger turned the tile green and wrote nothing. The fifth place I tried to put its file worked. About thirteen hours after the first of those builds, I moved the file to the SD card on principle, and well after midnight I found it had written nothing again. The tile itself, the part with actual logic in it, took one build.

The tile lives on MeshLauncher, the home screen I wrote for my HTC Desire Z, a 2010 phone on CyanogenMod 7 (Android 2.3, a community build) where I had started replacing stock apps with small ones of my own. MeshLauncher runs as UID 1000, the system user, because this build trusts the platform key it is signed with. Hold on to that UID; it is the villain. The tile shows the phone's current draw from a kernel file, smem_text, which the previous post takes apart. Tap it and it logs one CSV line every ten seconds. This post is the day it took to find a directory that would accept those lines.

HTC Desire Z battery drain in milliamps, straight from sysfs

Sun, 19 Oct 2025 00:00:00 +0000

The battery icon said 100% for the whole session, and it was telling the truth. The phone was on a USB cable and full, so 100% was the correct answer to a question I had stopped asking. The number I wanted sat one layer down. In one 70-second stretch of my log, the phone's estimated time left on a full charge went from 6.8 hours to 15.3 and the percentage did not twitch. I have a soft spot for a gauge that is accurate and useless at the same time. This one gets a place on the shelf.

Packing a battery-first kernel into an HTC Desire Z boot.img

Thu, 07 Aug 2025 00:00:00 +0000

Before I built a kernel for my HTC Desire Z, I wrote a plan for it, and the plan was confident about the end. Build the kernel and its modules, dump the boot partition, take the image apart, swap the kernel, put it back, flash it, check the frequency table, measure idle current. The middle of that, everything between "dump" and "flash", was a single comment line. I wrote that line. I have some notes for the man who wrote it.

Desire Z undervolt: a battery kernel next to CONFIG_JESUS_PHONE

Mon, 21 Apr 2025 00:00:00 +0000

The whole job, in the order it happened: twelve minutes of reading kernel source and writing a plan, a defconfig, an undervolt, three build failures, seven hours in which nobody touched it, a fourth build failure, a successful build, one fastboot flash boot, and a phone that came back up on a kernel I had compiled myself. The phone is my HTC Desire Z, the 2010 keyboard slider that runs CyanogenMod 7 (Android 2.3) in this series, and that I had just told, in so many words, to put its battery ahead of everything else. Speed second. Fun, apparently, third.