Gabriel Brown
816ea68f9a
With I2C access granted, the helper still found nothing: every connected monitor was probed on the wrong bus. A connector has two. The `ddc` symlink points at the classic I2C line that carries EDID on HDMI and DVI. DisplayPort carries DDC/CI over the AUX channel instead, which appears as a child directory of the connector. Both exist on a DP connector and both resolve, so the wrong choice looks entirely reasonable and simply finds no monitor: this machine's DP-2 has ddc -> i2c-5, where ddcutil reports "No monitor detected", while its AUX child i2c-9 answers VCP 0x10 immediately. This is the guess the previous commit said was unverified, and it was wrong in the way that mattered. Enumerating from sysfs is still right -- it gives the connector name Hyprland uses and skips empty connectors -- but it has to prefer the AUX child and fall back to the symlink. The fixture now mirrors sysfs properly: /sys/class/drm/<connector> is a SYMLINK to the real device directory, and `find` does not follow the path it is given. A fixture built from plain directories passes whether or not the code resolves the symlink first, which is a test that agrees with itself rather than with the kernel. Verified on hardware: the Kuycon P20 reports 100%, accepts 70 and returns to 100, and the media keys move it through codex's OSD path. Both bus-selection mistakes are now caught by the contract. Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L
164 lines
7.0 KiB
Bash
Executable File
164 lines
7.0 KiB
Bash
Executable File
#!/usr/bin/env bash
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# panama-brightness enumerates monitors from sysfs and speaks DDC/CI to them.
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#
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# The parts worth pinning down are the ones that decide whether a slider appears
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# at all, and whether it appears attached to the right screen:
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#
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# * only connectors with something plugged in are probed, because probing an
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# empty bus costs a timeout each and there are fourteen of them here;
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# * a panel that cannot report brightness is omitted rather than shown as a
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# control that does nothing;
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# * the connector name matches what Hyprland calls the output, since the UI
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# joins on it to get the monitor's description;
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# * no I2C access produces the udev command that fixes it, not "no displays".
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#
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# Runs entirely against fixtures. Real monitors are never touched: both the
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# sysfs root and the device root are redirected, and ddcutil is replaced on PATH.
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set -uo pipefail
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repo_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
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helper="$repo_dir/config/dot/quickshell/scripts/panama-brightness"
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fail() {
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printf 'brightness helper contract: %s\n' "$1" >&2
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exit 1
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}
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fixture="$(mktemp -d /tmp/panama-brightness.XXXXXX)"
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trap 'rm -rf "$fixture"' EXIT
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mkdir -p "$fixture/drm" "$fixture/dev" "$fixture/bin" "$fixture/i2c"
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# Two connectors with a monitor, two without. DP-2 answers DDC; DP-3 is
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# connected but does not implement brightness. HDMI-A-1 and DP-1 are empty and
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# must never be probed at all.
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# A connector has an EDID bus (the `ddc` symlink) and, on DisplayPort, an AUX
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# bus that appears as a child directory. DDC/CI rides the AUX channel where one
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# exists, and the `ddc` line answers nothing on a DP connector even though it
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# still resolves -- so the aux argument here is what a real DisplayPort monitor
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# looks like, and omitting it is what HDMI and DVI look like.
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make_connector() {
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local name="$1" ddc_bus="$2" status="$3" aux_bus="${4:-}"
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local device="$fixture/devices/$name"
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# /sys/class/drm/<connector> is a SYMLINK to the real device directory, and
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# this fixture mirrors that rather than using a plain directory. It matters:
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# `find` does not follow the path it is given, so code that searches the
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# unresolved path finds nothing while appearing to work anywhere the entry
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# happens to be a real directory.
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mkdir -p "$device"
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printf '%s\n' "$status" >"$device/status"
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mkdir -p "$fixture/i2c/i2c-$ddc_bus"
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ln -sfn "$fixture/i2c/i2c-$ddc_bus" "$device/ddc"
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[[ -n "$aux_bus" ]] && mkdir -p "$device/i2c-$aux_bus"
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mkdir -p "$fixture/drm"
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ln -sfn "$device" "$fixture/drm/$name"
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return 0
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}
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# DP-2 is the DisplayPort case: its EDID line is bus 5, which answers nothing,
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# and its AUX child is bus 9, which does. Choosing bus 5 here finds no monitor
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# at all, which is exactly the bug this pins down.
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make_connector card1-DP-1 4 disconnected
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make_connector card1-DP-2 5 connected 9
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make_connector card1-DP-3 6 connected
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make_connector card1-HDMI-A-1 7 disconnected
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# has_accessible_bus only needs one readable/writable node to exist.
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touch "$fixture/dev/i2c-5"
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# Stub ddcutil. Records every bus it is asked about so the test can prove the
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# disconnected ones were skipped. Bus 6 refuses, standing in for a panel without
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# VCP 0x10.
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#
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# Bus 5 reports its brightness out of 200 rather than 100. Most panels do use
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# 100, which is exactly the problem: with a maximum of 100 the scaling
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# arithmetic is the identity, so a helper that ignored the reported maximum
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# entirely would pass every assertion. 200 makes reads and writes that skip the
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# conversion visibly wrong.
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cat >"$fixture/bin/ddcutil" <<'STUB'
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#!/usr/bin/env bash
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bus=""
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args=("$@")
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for ((i = 0; i < ${#args[@]}; i++)); do
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[[ "${args[$i]}" == "--bus" ]] && bus="${args[$((i + 1))]}"
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done
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printf '%s\n' "$bus" >>"$DDCUTIL_PROBE_LOG"
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for arg in "$@"; do
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if [[ "$arg" == "setvcp" ]]; then
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printf 'set %s %s\n' "$bus" "${args[-1]}" >>"$DDCUTIL_SET_LOG"
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exit 0
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fi
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done
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case "$bus" in
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9) printf 'VCP 10 C 120 200\n'; exit 0 ;;
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*) exit 1 ;;
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esac
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STUB
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chmod +x "$fixture/bin/ddcutil"
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export DDCUTIL_PROBE_LOG="$fixture/probes.log"
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export DDCUTIL_SET_LOG="$fixture/sets.log"
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: >"$DDCUTIL_PROBE_LOG"
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: >"$DDCUTIL_SET_LOG"
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run_helper() {
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PATH="$fixture/bin:$PATH" \
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PANAMA_BRIGHTNESS_DRM_ROOT="$fixture/drm" \
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PANAMA_BRIGHTNESS_DEV_ROOT="$fixture/dev" \
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"$helper" "$@"
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}
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# ── Enumeration ──────────────────────────────────────────────────────────────
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listing="$(run_helper list)"
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jq -e . >/dev/null 2>&1 <<<"$listing" || fail "list did not emit JSON: $listing"
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[[ "$(jq -r '.displays | length' <<<"$listing")" == "1" ]] \
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|| fail "expected exactly one controllable display, got: $listing"
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[[ "$(jq -r '.displays[0].connector' <<<"$listing")" == "DP-2" ]] \
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|| fail "the connector name must match Hyprland's output name: $listing"
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# The AUX bus, not the EDID bus its `ddc` symlink points at.
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[[ "$(jq -r '.displays[0].bus' <<<"$listing")" == "9" ]] \
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|| fail "the display was mapped to its EDID bus instead of its DisplayPort AUX bus, where nothing answers: $listing"
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# 120 of a maximum of 200 is 60%.
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[[ "$(jq -r '.displays[0].value' <<<"$listing")" == "60" ]] \
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|| fail "brightness was not read as a percent of the reported maximum: $listing"
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[[ "$(jq -r '.error' <<<"$listing")" == "" ]] \
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|| fail "a successful listing must not carry an error: $listing"
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# A connected panel that cannot report brightness is dropped, not listed.
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jq -e '.displays | map(.connector) | index("DP-3") == null' >/dev/null <<<"$listing" \
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|| fail 'a display without VCP 0x10 was listed as controllable'
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# ── Disconnected connectors are never probed ─────────────────────────────────
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if grep -qxE '4|7' "$DDCUTIL_PROBE_LOG"; then
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fail "a disconnected connector was probed -- each empty bus costs a timeout: $(tr '\n' ' ' <"$DDCUTIL_PROBE_LOG")"
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fi
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# ── Writes scale to the reported maximum ─────────────────────────────────────
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run_helper set 9 40
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[[ "$(tail -1 "$DDCUTIL_SET_LOG")" == "set 9 80" ]] \
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|| fail "set did not scale to the display's maximum: $(cat "$DDCUTIL_SET_LOG")"
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run_helper set 9 500
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[[ "$(tail -1 "$DDCUTIL_SET_LOG")" == "set 9 200" ]] \
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|| fail "an out-of-range percent was not clamped: $(cat "$DDCUTIL_SET_LOG")"
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# ── No I2C access explains itself ────────────────────────────────────────────
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rm -f "$fixture/dev"/i2c-*
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denied="$(run_helper list)"
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[[ "$(jq -r '.displays | length' <<<"$denied")" == "0" ]] \
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|| fail "displays were reported without I2C access: $denied"
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grep -q 'udevadm' <<<"$(jq -r '.error' <<<"$denied")" \
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|| fail "the no-access error must name the command that fixes it, got: $(jq -r '.error' <<<"$denied")"
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printf 'brightness helper contract: PASS\n'
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