gc_bba_test: fix inverted EXI error checks; builds clean

libogc's EXI functions return '1 on success, <=0 on error', but every call
site tested '== 0'.  A -1 error return therefore read as success, so a failed
EXI_Lock or EXI_Select would fall through and the subsequent transfer would
produce garbage reported as a misleading test failure rather than an EXI
error.  All six call sites now test <= 0.

Also retries EXI_Lock for ~100 ms: it fails outright rather than blocking when
another subsystem holds the channel, and Swiss or a libogc driver may hold it
briefly -- without the retry a transient collision surfaces as a test failure.

Builds clean with devkitPPC 16.1.0 / GCC 16, no warnings: 172 KB .dol.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.devcontainer/Dockerfile

@@ -1,3 +1,8 @@
+# devkitPro's official image, used only as a source for the GameCube toolchain
+# (see the devkitPPC section below).  `:latest` tracks devkitPro releases; pin a
+# dated tag (e.g. :20250527) if a toolchain update ever breaks the build.
+FROM devkitpro/devkitppc:latest AS devkitppc
+
 FROM debian:sid-slim
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
@@ -5,6 +10,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     git \
     git-lfs \
+    make \
     sudo \
     python3 \
     python3-venv \
@@ -52,21 +58,24 @@ RUN pip install --no-cache-dir pyftdi pyserial
 
 # ── GameCube homebrew toolchain (devkitPPC + libogc) ────────────────────────
 # Needed to build the on-console BBA test app in `gc_bba_test/` into a .dol.
-# devkitPro does NOT publish a .deb on GitHub -- the Debian package only exists
-# in their own apt repo -- so this uses their maintained installer script, which
-# adds the repo, imports the key and installs dkp-pacman.  `gamecube-dev` is a
-# package GROUP (devkitPPC, libogc, libfat, tools incl. elf2dol).
 #
-# NOTE this pulls from apt.devkitpro.org / pkg.devkitpro.org.  Those hosts are
+# Copied out of devkitPro's official `devkitpro/devkitppc` image rather than
-# blocked (HTTP 403) from inside the running container's network egress, but a
+# installed with their `install-devkitpro-pacman` script: apt.devkitpro.org and
-# host-side `docker build` reaches them fine -- which is why this lives in the
+# pkg.devkitpro.org sit behind Cloudflare, which answers curl/wget/scripted
-# Dockerfile rather than being installed at runtime.  Adds roughly 1.5-2 GB.
+# fetches with HTTP 403 (browser user-agents get 200) -- from the host's
-RUN curl -fsSL https://apt.devkitpro.org/install-devkitpro-pacman -o /tmp/install-devkitpro-pacman \
+# `docker build` too, not just from inside the container.  The Docker image is
- && chmod +x /tmp/install-devkitpro-pacman \
+# devkitPro's sanctioned route for CI/containers and needs no network access to
- && yes | /tmp/install-devkitpro-pacman \
+# their hosts.  The binaries only link against libc, so they run fine on sid.
- && dkp-pacman -S --noconfirm gamecube-dev \
+#
- && dkp-pacman -Scc --noconfirm \
+# Only the GameCube/PPC parts are copied (~540 MB); devkitARM, wut and the
- && rm -f /tmp/install-devkitpro-pacman
+# Wii/Wii U portlibs from the source image are skipped.
+COPY --from=devkitppc /opt/devkitpro/devkitPPC         /opt/devkitpro/devkitPPC
+COPY --from=devkitppc /opt/devkitpro/libogc            /opt/devkitpro/libogc
+COPY --from=devkitppc /opt/devkitpro/tools             /opt/devkitpro/tools
+COPY --from=devkitppc /opt/devkitpro/cmake             /opt/devkitpro/cmake
+COPY --from=devkitppc /opt/devkitpro/licenses          /opt/devkitpro/licenses
+COPY --from=devkitppc /opt/devkitpro/portlibs/ppc      /opt/devkitpro/portlibs/ppc
+COPY --from=devkitppc /opt/devkitpro/portlibs/gamecube /opt/devkitpro/portlibs/gamecube
 
 ENV DEVKITPRO=/opt/devkitpro
 ENV DEVKITPPC=/opt/devkitpro/devkitPPC

.gitignore

@@ -33,3 +33,9 @@ hardware/re-bba-rb/re-bba-rb-eeprom.bin
 *.swp
 .history/
 build_w5100test/
+
+# GameCube test app build products
+gc_bba_test/build/
+gc_bba_test/*.elf
+gc_bba_test/*.dol
+gc_bba_test/*.map

gc_bba_test/README.md

@@ -65,3 +65,10 @@ fault. `bba_read()` clocks exactly `len`; don't "round up" for convenience.
 **TXDATA takes one byte per transaction.** The register file's effective
 address auto-increments per data byte, so a 4-byte write to 0x48 would spill
 into 0x49–0x4B. `bba_tx_bytes()` does it correctly.
+
+## Build status
+
+Builds clean (no warnings) with devkitPPC 16.1.0 / GCC 16 in the devcontainer:
+`gc_bba_test.dol`, ~172 KB, entry `0x80003100`.
+
+`.gitignore` excludes the build products — run `make` to produce the `.dol`.

gc_bba_test/source/bba.c

@@ -1,5 +1,6 @@
 #include "bba.h"
 #include <string.h>
+#include <unistd.h>
 
 u32 bba_speed = EXI_SPEED32MHZ;   /* nominal name; ~27 MHz in reality */
 
@@ -17,8 +18,17 @@ static u16 hdr(u16 addr, u32 len, int write)
 
 static int begin(void)
 {
-	if (EXI_Lock(BBA_EXI_CHAN, BBA_EXI_DEV, NULL) == 0) return -1;
+	int tries;
-	if (EXI_Select(BBA_EXI_CHAN, BBA_EXI_DEV, bba_speed) == 0) {
+	/* EXI_Lock fails outright (rather than blocking) when another subsystem
+	 * holds the channel -- Swiss or a libogc driver may have it briefly.
+	 * Retry for ~100 ms before giving up so a transient collision does not
+	 * surface as a test failure. */
+	for (tries = 0; tries < 100; tries++) {
+		if (EXI_Lock(BBA_EXI_CHAN, BBA_EXI_DEV, NULL) > 0) break;
+		usleep(1000);
+	}
+	if (tries == 100) return -1;
+	if (EXI_Select(BBA_EXI_CHAN, BBA_EXI_DEV, bba_speed) <= 0) {
 		EXI_Unlock(BBA_EXI_CHAN);
 		return -2;
 	}
@@ -34,8 +44,8 @@ static void end(void)
 static int put_hdr(u16 addr, u32 len, int write)
 {
 	u16 h = hdr(addr, len, write);
-	if (EXI_Imm(BBA_EXI_CHAN, &h, 2, EXI_WRITE, NULL) == 0) return -3;
+	if (EXI_Imm(BBA_EXI_CHAN, &h, 2, EXI_WRITE, NULL) <= 0) return -3;
-	if (EXI_Sync(BBA_EXI_CHAN) == 0) return -4;
+	if (EXI_Sync(BBA_EXI_CHAN) <= 0) return -4;
 	return 0;
 }
 
@@ -49,7 +59,7 @@ int bba_read(u16 addr, void *buf, u32 len)
 	 * header and prefetches the response into its TX FIFO.  Separate EXI_Imm
 	 * calls give us that gap for free. */
 	memset(buf, 0, len);
-	if (EXI_ImmEx(BBA_EXI_CHAN, buf, len, EXI_READ) == 0) { end(); return -5; }
+	if (EXI_ImmEx(BBA_EXI_CHAN, buf, len, EXI_READ) <= 0) { end(); return -5; }
 	end();
 	return 0;
 }
@@ -62,7 +72,7 @@ int bba_write(u16 addr, const void *buf, u32 len)
 	memcpy(tmp, buf, len);
 	if ((rc = begin()) < 0) return rc;
 	if ((rc = put_hdr(addr, len, 1)) < 0) { end(); return rc; }
-	if (EXI_ImmEx(BBA_EXI_CHAN, tmp, len, EXI_WRITE) == 0) { end(); return -6; }
+	if (EXI_ImmEx(BBA_EXI_CHAN, tmp, len, EXI_WRITE) <= 0) { end(); return -6; }
 	end();
 	return 0;
 }
@@ -89,7 +99,7 @@ int bba_stream(u16 addr, void *buf, u32 len)
 	 * bytes as we actually want. */
 	if ((rc = put_hdr(addr, 4, 0)) < 0) { end(); return rc; }
 	memset(buf, 0, len);
-	if (EXI_ImmEx(BBA_EXI_CHAN, buf, len, EXI_READ) == 0) { end(); return -5; }
+	if (EXI_ImmEx(BBA_EXI_CHAN, buf, len, EXI_READ) <= 0) { end(); return -5; }
 	end();
 	return 0;
 }

gc_bba_test/source/tests.c

@@ -2,6 +2,7 @@
 #include "bba.h"
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 #include <ogc/lwp_watchdog.h>
 
 int g_ncra_reset_done = 0;