build(rpm): let the spec build a client-only aarch64 RPM

The blocker was never ExclusiveArch — it was that %build builds host +
tray + client together and %install lays down the host unconditionally,
with no way to express "client only". `%bcond_without host` (default ON,
so an x86_64 build is unchanged) now gates the host binary, the tray, the
headless-session data, the firewalld services, the main %post and the bare
%files section. Omitting %files for the MAIN package is the load-bearing
part: it is what stops rpm emitting an empty `punktfunk` alongside
punktfunk-client.

build-rpm.sh exposes it as PF_WITHOUT_HOST=1 and skips the libcuda stub
regeneration and the libcuda leak check, neither of which means anything
without the host.

Verified two ways. `rpmspec -P` shows the default expansion still carrying
3 host install lines, the tray build and one bare %files, while
--without host carries none of those and one %files client. And a real
rpmbuild in a native aarch64 Fedora 43 container produced
punktfunk-client-*.aarch64.rpm with correct aarch64 sonames
(libc.so.6(GLIBC_2.17), libSDL3.so.0, libavcodec.so.61) and no main
package.

Not a cross-compile: %build runs cargo for the build machine's arch, so
this wants an arm64 builder. No CI leg yet — deliberate.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

packaging/rpm/README.md

@@ -123,3 +123,24 @@ docker run --rm -v "$PWD:/src" -w /src punktfunk-fedora-rpm \
 
 A plain `rpmbuild`/COPR build with no `pf_version`/`pf_release` defines produces `0.3.0-1` (the
 spec defaults).
+
+### aarch64 — the client RPM
+
+The **client** builds for aarch64; the **host** does not (its encode stack is NVENC/QSV/AMF, all
+x86). `PF_WITHOUT_HOST=1` drops the host binary, the tray, the headless-session data, the
+firewalld services and the main package's `%files`, leaving exactly one RPM: `punktfunk-client`.
+Omitting the main `%files` is what keeps rpm from emitting an empty `punktfunk` next to it.
+
+This is **not** a cross-compile — `%build` runs cargo for the host architecture, so run it on an
+arm64 machine (or an emulated arm64 container, which is very slow):
+
+```sh
+docker build --platform linux/arm64 -f ci/fedora-rpm.Dockerfile -t punktfunk-fedora-rpm-arm64 ci
+docker run --rm --platform linux/arm64 -v "$PWD:/src" -w /src punktfunk-fedora-rpm-arm64 \
+  bash -lc 'git config --global --add safe.directory /src && \
+            PF_VERSION=0.0.1 PF_WITHOUT_HOST=1 bash packaging/rpm/build-rpm.sh'
+# -> dist/punktfunk-client-0.0.1-1.fcNN.aarch64.rpm
+```
+
+`PF_WITHOUT_HOST=1` works on x86_64 too, if you only want the client RPM. The flag is orthogonal
+to the architecture; it is just that aarch64 has no other option.

packaging/rpm/build-rpm.sh

@@ -19,6 +19,11 @@ WEB_OPT=()
 # requirement as web; default off so a bare `rpmbuild`/COPR still works.
 SCRIPTING_OPT=()
 [ "${PF_WITH_SCRIPTING:-0}" = "1" ] && SCRIPTING_OPT=(--with scripting)
+# PF_WITHOUT_HOST=1 drops the host binary, the tray and the main package, leaving only
+# punktfunk-client. This is what an aarch64 build uses: the client is portable, the host's encode
+# stack (NVENC/QSV/AMF) is x86. Harmless on x86_64 too, if you only want the client RPM.
+HOST_OPT=()
+[ "${PF_WITHOUT_HOST:-0}" = "1" ] && HOST_OPT=(--without host)
 ROOTDIR="$(cd "$(dirname "$0")/../.." && pwd)"
 cd "$ROOTDIR"
 
@@ -39,7 +44,7 @@ git archive --format=tar.gz --prefix="punktfunk-${PF_VERSION}/" \
 # undefined cuStreamCreateWithPriority/cuMemcpy2DAsync_v2/…; this regen supersedes it.) Defining
 # extra unused symbols is harmless; a missing one fails the link. Only when /usr/lib64 is writable
 # (CI image runs as root) — COPR/mock provides the real cuda-cudart-devel stub instead.
-if [ "$(id -u)" = 0 ] && [ -d /usr/lib64 ]; then
+if [ "${PF_WITHOUT_HOST:-0}" != "1" ] && [ "$(id -u)" = 0 ] && [ -d /usr/lib64 ]; then
   CU_SYMS="$(grep -rhoE '\bcu[A-Z][A-Za-z0-9_]*' crates/punktfunk-host/src/ | sort -u || true)"
   if [ -n "$CU_SYMS" ]; then
     STUB_C="$(mktemp --suffix=.c)"
@@ -55,7 +60,7 @@ fi
 # resolves them from RPMs. Our builder image provides the toolchain via rustup (so
 # rust-toolchain.toml's pinned channel works) and the -devel libs via dnf, neither of which
 # rpmbuild's RPM-level check sees — skip it; a genuinely missing dep fails the compile/link.
-rpmbuild -bb --nodeps "${WEB_OPT[@]}" "${SCRIPTING_OPT[@]}" \
+rpmbuild -bb --nodeps "${WEB_OPT[@]}" "${SCRIPTING_OPT[@]}" "${HOST_OPT[@]}" \
   --define "_topdir $TOP" \
   --define "pf_version ${PF_VERSION}" \
   --define "pf_release ${PF_RELEASE}" \
@@ -63,6 +68,12 @@ rpmbuild -bb --nodeps "${WEB_OPT[@]}" "${SCRIPTING_OPT[@]}" \
 
 mkdir -p dist
 find "$TOP/RPMS" -name '*.rpm' -exec cp -v {} dist/ \;
+# The libcuda leak check applies to the HOST package (the only thing that links the driver); a
+# client-only build has no such package to inspect.
+if [ "${PF_WITHOUT_HOST:-0}" = "1" ]; then
+  echo "== client-only build: no host RPM, libcuda check not applicable =="
+else
   echo "== Requires (must NOT contain libcuda) =="
   rpm -qp --requires dist/punktfunk-${PF_VERSION}-*.rpm 2>/dev/null | grep -iE 'cuda|nvidia' \
     && echo "  !! NVIDIA/CUDA leak !!" || echo "  clean"
+fi

packaging/rpm/punktfunk.spec

@@ -31,10 +31,10 @@ URL:            https://git.unom.io/unom/punktfunk
 # COPR SCM builds provide the checkout; for a tarball build, drop a git archive here:
 Source0:        %{name}-%{version}.tar.gz
 
-# punktfunk-host is Linux-only and links system FFmpeg/PipeWire/Opus. x86_64 only for now: encode
+# punktfunk-host is Linux-only and links system FFmpeg/PipeWire/Opus. The HOST is x86_64 only —
-# is NVENC (desktop NVIDIA) and no aarch64 build is produced/published by CI — claiming aarch64
+# its encode stack is NVENC/QSV/AMF — but the CLIENT builds and runs fine on aarch64, so the spec
-# here would advertise an arch we never ship. Re-add aarch64 once there's an arm64 build leg.
+# accepts both arches and `--without host` (below) selects the client-only build.
-ExclusiveArch:  x86_64
+ExclusiveArch:  x86_64 aarch64
 
 # The zerocopy FFI links the NVIDIA driver's libcuda.so.1; rpm's auto-dep generator would turn
 # that into a hard Requires on libcuda.so.1 (and we never want to pin the driver — NVENC/EGL come
@@ -55,6 +55,14 @@ ExclusiveArch:  x86_64
 # Debian punktfunk-scripting .deb.
 %bcond_with scripting
 
+# The HOST half of this spec (the punktfunk package itself + the tray). ON by default, so an
+# ordinary x86_64 build is unchanged. `--without host` drops the host binary, the tray, the
+# headless-session data, the firewalld services and the main %%files section entirely, leaving
+# only punktfunk-client — which is what an aarch64 build produces, since the host's encode stack
+# (NVENC/QSV/AMF) is x86 and the client's is not. Omitting the main %%files is what stops rpm
+# from emitting an empty `punktfunk` package alongside the client.
+%bcond_without host
+
 # --- Build toolchain ---------------------------------------------------------
 BuildRequires:  cargo
 BuildRequires:  rust
@@ -211,14 +219,21 @@ export PUNKTFUNK_BUILD_VERSION="%{version}-%{release}"
 # with real RFI (clean P-frame recovery anchor via DPB reference slots; design/linux-vulkan-video-encode.md).
 # Pure Rust `ash` (no new lib / no link-time dep); default on for HEVC (PUNKTFUNK_VULKAN_ENCODE=0 opts
 # back to libav VAAPI), and a failed open falls back to VAAPI so unsupported devices degrade gracefully.
+%if %{with host}
 cargo build --release --locked --features punktfunk-host/nvenc,punktfunk-host/vulkan-encode \
   -p punktfunk-host -p punktfunk-client-linux -p punktfunk-client-session
+%else
+# Client-only (aarch64): no host crate, so none of the encode features apply.
+cargo build --release --locked -p punktfunk-client-linux -p punktfunk-client-session
+%endif
 # The status tray in its OWN cargo invocation — load-bearing, not tidiness. Cargo unifies features
 # across everything in one build, so co-building the tray with the host pulls the host's
 # ashpd -> zbus/tokio onto the tray's shared zbus; the tray (ksni async-io + blocking, no tokio
 # runtime by design) then panics at startup ("there is no reactor running, must be called from the
 # context of a Tokio 1.x runtime"). Built alone, its zbus stays on async-io. (Same split the .deb does.)
+%if %{with host}
 cargo build --release --locked -p punktfunk-tray
+%endif
 
 %if %{with web}
 # Management web console: build the Nitro SSR bundle with bun (the `bun` preset + our Bun.serve
@@ -243,6 +258,7 @@ fi
 %endif
 
 %install
+%if %{with host}
 # Binary
 install -Dm0755 target/release/punktfunk-host %{buildroot}%{_bindir}/punktfunk-host
 
@@ -294,6 +310,7 @@ for sz in 22x22 48x48; do
     install -Dm0644 "$png" %{buildroot}%{_datadir}/icons/hicolor/$sz/apps/"$(basename "$png")"
   done
 done
+%endif
 
 # --- client subpackage ---
 install -Dm0755 target/release/punktfunk-client %{buildroot}%{_bindir}/punktfunk-client
@@ -311,6 +328,7 @@ install -Dm0644 scripts/70-punktfunk-client.rules \
 install -Dm0644 scripts/99-punktfunk-client-net.conf \
                 %{buildroot}%{_prefix}/lib/sysctl.d/99-punktfunk-client-net.conf
 
+%if %{with host}
 # Headless session helpers + example config + OpenAPI doc (reference material).
 install -d %{buildroot}%{_datadir}/%{name}/headless
 install -Dm0755 scripts/headless/run-headless-kde.sh   %{buildroot}%{_datadir}/%{name}/headless/run-headless-kde.sh
@@ -344,6 +362,7 @@ install -Dm0644 packaging/linux/punktfunk-native.xml \
 # Web console opener (TCP 47992) — only meaningful with the web subpackage, opened deliberately.
 install -Dm0644 packaging/linux/punktfunk-web.xml \
                 %{buildroot}%{_prefix}/lib/firewalld/services/punktfunk-web.xml
+%endif
 
 %if %{with web}
 # --- web console subpackage (punktfunk-web) ---
@@ -383,6 +402,7 @@ chmod 0755 %{buildroot}%{_bindir}/punktfunk-scripting
 install -Dm0644 scripts/punktfunk-scripting.service %{buildroot}%{_userunitdir}/punktfunk-scripting.service
 %endif
 
+%if %{with host}
 %files
 %license LICENSE-MIT LICENSE-APACHE THIRD-PARTY-NOTICES.txt
 %doc README.md packaging/README.md
@@ -407,6 +427,7 @@ install -Dm0644 scripts/punktfunk-scripting.service %{buildroot}%{_userunitdir}/
 %config(noreplace) /etc/gamescope-session-plus/sessions.d/steam
 %dir %{_datadir}/%{name}
 %{_datadir}/%{name}/*
+%endif
 
 %files client
 %license LICENSE-MIT LICENSE-APACHE THIRD-PARTY-NOTICES.txt
@@ -450,6 +471,7 @@ udevadm trigger --subsystem-match=hidraw 2>/dev/null || :
 # rpm-ostree it takes effect on the next boot into the layered deployment).
 sysctl -p %{_prefix}/lib/sysctl.d/99-punktfunk-client-net.conf >/dev/null 2>&1 || :
 
+%if %{with host}
 %post
 # Reload udev so /dev/uinput picks up the new rule without a reboot (best-effort).
 udevadm control --reload-rules 2>/dev/null || :
@@ -474,6 +496,7 @@ if command -v punktfunk-host >/dev/null 2>&1; then
         echo "$conflict"
     fi
 fi
+%endif
 
 %if %{with web}
 %post web