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feat(vcd): adaptive BDMA source seek -- Custom dir, boot device, then game device (FifthFox FR) #244

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Merged
NathanNeurotic merged 1 commit into from
Jul 20, 2026
Merged

feat(vcd): adaptive BDMA source seek -- Custom dir, boot device, then game device (FifthFox FR) #244

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71 changes: 65 additions & 6 deletions src/vcdsupport.c
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Original file line number Diff line number Diff line change
Expand Up @@ -762,17 +762,79 @@ int vcdEquipBdma(int source, int mode, char *diag, int diagSize)
return (mr != 0) ? mr : 0;
}

const char *suffix = vcdBdmaSuffix[mode];
char src0[96], src1[96];

@gemini-code-assist gemini-code-assist Bot Jul 20, 2026

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medium

With the introduction of the adaptive seek order, src0 and src1 can now hold paths derived from gPopstarterPath (which can be up to 256 characters). A limit of 96 bytes is sufficient for root-level device paths, but can cause silent truncation for deeply nested custom POPSTARTER paths. Increasing the buffer size of src0 and src1 to 256 bytes prevents truncation and aligns with other path buffers in this file.

    char src0[256], src1[256];

int found = 0;

// FifthFox's adaptive seek order (maintainer-approved): look for the variant pair at the CUSTOM
// POPSTARTER.ELF's own folder first (a user who relocated POPSTARTER keeps its drivers beside it),
// then the BOOT (cwd) device's POPS/ folder, and only then the game device's family search below.
// This is also the FAST order: both pre-candidates live on ALREADY-LOADED stacks (we booted from
// one and are launching from the other), so a hit here costs a few open() probes and skips the
// family search's transport force-loads and bounded mount waits entirely.
{
char preBuf[2][96];

@gemini-code-assist gemini-code-assist Bot Jul 20, 2026

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medium

Similarly to src0 and src1, preBuf should be increased to 256 bytes to accommodate the potentially long custom POPSTARTER paths from gPopstarterPath without skipping the search due to the bounds check n < (int)sizeof(preBuf[0]).

        char preBuf[2][256];

const char *pre[2];
int npre = 0;

if (gPopstarterDevice == POPS_DEV_CUSTOM && gPopstarterPath[0] != '\0') {
const char *s1 = strrchr(gPopstarterPath, '/');
const char *s2 = strrchr(gPopstarterPath, '\\'); // SMB custom paths use backslashes
// Not `(s2 > s1)`: relationally comparing a possibly-NULL pointer is UB in ISO C.
const char *sl = s1;
if (s2 != NULL && (sl == NULL || s2 > sl))
sl = s2;
int n = (sl != NULL) ? (int)(sl - gPopstarterPath) + 1 : 0; // keep the separator
if (n > 0 && n < (int)sizeof(preBuf[0])) {
memcpy(preBuf[npre], gPopstarterPath, n);
preBuf[npre][n] = '\0';
pre[npre] = preBuf[npre];
npre++;
}
}
if (gBootDir[0] != '\0') {
const char *colon = strchr(gBootDir, ':');
int n = (colon != NULL) ? (int)(colon - gBootDir) + 1 : 0;
if (n > 0 && (n + (int)sizeof("/" POPS_FOLDER "/")) < (int)sizeof(preBuf[1])) {
memcpy(preBuf[npre], gBootDir, n);
preBuf[npre][n] = '\0';
strcat(preBuf[npre], "/" POPS_FOLDER "/");
pre[npre] = preBuf[npre];
npre++;
}
}

for (int i = 0; i < npre && !found; i++) {
snprintf(src0, sizeof(src0), "%s%s.%s", pre[i], vcdBdmaModule[0], suffix);
snprintf(src1, sizeof(src1), "%s%s.%s", pre[i], vcdBdmaModule[1], suffix);
int f0 = open(src0, O_RDONLY);
LOG("[BDMA] pre-probe %s -> %d\n", src0, f0);
if (f0 < 0)
continue;
close(f0);
int f1 = open(src1, O_RDONLY);
LOG("[BDMA] pre-probe %s -> %d\n", src1, f1);
if (f1 < 0)
continue;
close(f1);
found = 1;
}
}

// Resolve the SOURCE device(s) to read the variant files from. BDM sources are DIFFERENTIATED by
// driver: find EVERY mounted device whose driver matches the chosen type (USB / MX4SIO / internal
// exFAT HDD) and read from its massN: FILESYSTEM root -- the same path the device pages browse. OPL
// never mounts a typed ata0:/usb0:/mx4sio0: filesystem (those are block-device identities used only
// for launch binding), so the readable source path is always massN:/. Searching ALL matching slots,
// not just the first, covers a source family with two same-type devices when the variant files sit
// on the second one. MMCE has its own mmce0:/mmce1: slots.
// on the second one. MMCE has its own mmce0:/mmce1: slots. Skipped when the adaptive pre-probe
// above already found the pair.
const char *cands[MAX_BDM_DEVICES];
char bdmRoots[MAX_BDM_DEVICES][BDM_DEVICE_ROOT_MAX + 2];
int nc = 0;
if (source == VCD_BDMA_SRC_MMCE) {
if (found) {
// Adaptive pre-probe already located the pair -- no transport force-loads needed.
} else if (source == VCD_BDMA_SRC_MMCE) {
// Ensure mmceman is loaded even when MMCE games are off / Manual-not-started -- otherwise mmce0:/
// mmce1:/ are dead and nothing can be read. Then offer only slots that actually have a card, so
// the not-found diagnostic is honest ("no device" vs "device found, files missing").
Expand Down Expand Up @@ -803,10 +865,7 @@ int vcdEquipBdma(int source, int mode, char *diag, int diagSize)
}
}

const char *suffix = vcdBdmaSuffix[mode];
char src0[96], src1[96];
int found = 0;
for (int i = 0; i < nc; i++) {
for (int i = 0; i < nc && !found; i++) {
snprintf(src0, sizeof(src0), "%s" POPS_FOLDER "/%s.%s", cands[i], vcdBdmaModule[0], suffix);
snprintf(src1, sizeof(src1), "%s" POPS_FOLDER "/%s.%s", cands[i], vcdBdmaModule[1], suffix);
int f0 = open(src0, O_RDONLY);
Expand Down
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