007-pbp2c (tested): btrfs

Tow-Boot 2023.07-007 for the Pinebook Pro: everything in 007-pbp1, plus btrfs.

• Backlight turned off at kernel handoff: no garbage on screen between "Starting kernel" and the kernel's display driver (about 3 s into boot)
• Tow-Boot screen at brightness 40/255
• FDTOVERLAYS in extlinux.conf works
• 1 s boot menu countdown
• btrfs: Tow-Boot reads /boot (extlinux.conf, kernel, initramfs, dtb) from btrfs, using the default subvolume; zlib/lzo/zstd. Includes 6 btrfs fixes backported from U-Boot master, among them 6f0719e4c4 (zstd-compressed small files written by the kernel, e.g. an edited extlinux.conf, failed with failed to decompress: 70)
• U-Boot's start-up stack moved from 0x300000 to 0x03f00000 (as upstream U-Boot does now). Without this, adding btrfs makes the image overlap the stack and the board doesn't start: that's what happened to 007-pbp2

Status: tested on my Pinebook Pro (2026-10-13): boots from SPI; booted a kernel from a zstd-compressed btrfs (top-level subvolume, chainload test). Booting from a non-top-level default subvolume (@) not tested yet. The SD card installer image is built the same way as stock Tow-Boot's but wasn't tried.

Files:

• Tow-Boot.spi.bin: flash from Linux with flashcp (see the README; back up /dev/mtd0ro first)
• spi.installer.img.xz: SD card installer ("Flash firmware to SPI")
• SHA256SUMS

d828003d83da27fdbba8ea5f354707428c993421187bff38e9f98456f27d8d26  Tow-Boot.spi.bin
938c3c4aa405b1e97931b829a64b2ababf6677fda363e909a11c3765acb0963c  spi.installer.img
4fb13ac158d004ae7d50a68922354a8fa0cd559185a9acce3e96ba666323b1fe  spi.installer.img.xz