PAF · Platform — hardware, boot, storage, recovery (Arch era)

Load-bearing device facts. Add a line when something costs more than 2 minutes to relearn. pmOS-era snapshot preserved at evidence/platform-pmos-era.md — its Alpine/ash and pmOS-slot notes no longer apply.

Reaching the phone

USB (primary): ssh -F /dev/null -i ~/.ssh/ani -o BatchMode=yes casey@172.16.42.1 (NCM gadget, phone serves DHCP; laptop autoconfigures).
WiFi: DHCP on the LAN, drifts — check the router or nmcli on-device via USB first.
User casey, passwordless-sudo NO — sudo password 147147 (echo 147147 | sudo -S <cmd>). Never stream sudo-gated output through further pipes over SSH (silent truncation, repeatedly) — write to a file on the phone, pull it separately.
Shell is bash on Arch (systemd, GNU coreutils, pacman). The pmOS-era busybox/ash caveats are dead.
Serial fallback: ACM gadget → laptop-side ttyACM0; getty enabled on ttyGS0.

Slots & boot architecture

Slot A = Arch (ours). Slot B = LineageOS (Android, rooted, on the 4.9 vendor kernel). Slot B is the living downstream reference AND the fallback OS — never touch boot_b or Android's partitions.
Boot chain: ABL boots boot_a (Android bootimg v0, our kernel Image.gz with appended DTB + the pmOS-chain ramdisk — see build.md). Root is found by UUID from the baked cmdline.
qbootctl (in the device package since ef21637) marks the slot successful and provides reboot-to-android; closes the A/B retry-lockout that used to eat boots.
Switch to Android: sudo reboot bootloader → fastboot --set-active=b → fastboot reboot (and back with --set-active=a).

Storage (live table, verified on-device 2026-07-10)

UFS /dev/sda, GPT, 4096-byte sectors (sgdisk needs -a 256; a tool assuming 512B sectors will misread the table).

Part	Size	FS	Name	Role
sda21	42.9G	—	userdata	Android's, FBE-encrypted, NEVER TOUCH (near-formatted once — always verify identity before writing any partition)
sda22	10.0G	fat32	shared	Arch↔Android shared data, mounted /shared
sda23	253M	vfat	Arch_boot	staging/aux boot filesystem
sda24	66.2G	ext4	Arch_root	the Arch rootfs, `UUID=a094e031-ea89-4847-a299-082a0ae8c9ab`

persist lives on a different UFS LUN (sdf2) — physically immune to sda operations; mounted ro,nofail. Backup in ../blobs/ + ~/pixel3-backup/persist.img.

Boot-image A/B slots (boot_a/boot_b, 67MB each, partitions 11/12) are separate from the rootfs partitions above — fastboot flash boot_a is the only flash operation this project performs.

Recovery

TWRP: fastboot boot ~/Downloads/twrp-3.7.1_12-0-blueline.img (boot, not flash). Used for repartition-class work; a live pmOS/Arch root can't modify its own mounted partitions.
Known-good fallback kernel image (stmfts touch, pre-SWIRE display): ../staging/deploy-139aa/boot-139aa7748181-pmoschain.img → flash to boot_a. Its module tree is on the phone.
Full stock partition clone (2026-06-18) at ~/pixel3-backup/; LOS boot image at ~/Downloads/lineage-22.2-20260629-boot.img.
Last resort: slot B is a complete, working Android.

Hardware map (what's proven on this exact unit)

SoC sdm845, 4G RAM. Panel: LG SW43408 (DSC command-mode, 1080x2160) — settled from per-unit persist calibration data; the Samsung s6e3ha8/sec_ts DTBO fragments are the OTHER hardware variant, not ours.
Touch: ST FTS @ 0x49 on i2c-2 (888000 geni SE, GPI-DMA-only); reset tlmm 99 (active-low RESETB), IRQ tlmm 125, AP/SLPI bus switch tlmm 136.
OLED bias: PMI8998 LAB/IBB under SWIRE (DDIC hardware) control — see display.md.
WiFi wcn3990 (ath10k_snoc), BT (hci_uart/btqca), modem MPSS (see modem.md), sensors behind SLPI DSP (see slpi.md), audio WCD9340 over SLIMbus (working HiFi speaker, microphone and two-way calls; see audio.md).
Power button = pm8941_pwrkey → input event; volume keys GPIO.

Charging (pmi8998, `qcom_smbx`)

Two supplies: pmi8998-charger (the charger) and qcom-battery (fuel gauge). The charger IC does full CC/CV — trickle, pre, fast, full-on, taper — and BATTERY_CHARGER_STATUS_1 bits 0:2 report which stage it is in. Mainline read that register only to derive status, collapsing all five states into "Charging" and discarding the detail.

Since f08dc70b3 the driver exposes them:

attribute	register	notes
`charge_type`	`BATTERY_CHARGER_STATUS_1` (0x06)	read-only; Trickle/Fast/Standard
`constant_charge_current_max`	`FAST_CHARGE_CURRENT_CFG` (0x61)	25000µA/step, 8-bit
`voltage_max`	`FLOAT_VOLTAGE_CFG` (0x70)	`raw=(uV-3487500)/7500+1`; 4.4V → 122
`charge_control_end_threshold`	same as above	percentage form, 0-100

Lowering the float voltage is what caps the charge. The cell is held at whatever CV target is programmed, so 4.1V parks it near 80% and buys calendar life. Writes are bounded twice — by the DT cell rating (voltage-max-design-microvolt = <4400000> in sdm845-google-blueline.dts) and by what the 8-bit fields can encode, so neither an overcharge nor a silent masked-off write is possible.

These registers are volatile — every setting is lost on reboot. Use /etc/blueline-charge-limit + blueline-charge-limit.service to persist one. Front end is blueline-charge status|limit|current.

Not exposed by this driver: charge_full/charge_now (fuel gauge, see qcom-battery) and any charge scheduling — downstream's google_charger ran a taper state machine with DT tunables (google,chg-itaper, chg-soctaper); mainline has no equivalent and this patch does not add one.

Hard lessons (each cost real time — do not relearn)

Verify partition identity before any write (parted -s /dev/sda print
- blkid); an unlabeled lsblk row is not free space. The sda21 near-miss is the standing warning.
/tmp on the phone is tmpfs — never park artifacts there.
fastboot boot <img> has a ~60s hardware watchdog — flash, don't test-boot, anything that takes long to come up.
Trust the user's direct visual report of the glass over any remote telemetry — registers can say "on" while the panel shows black.

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