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[Feat] (MG_Remote): a read into a pixel pack buffer crosses as read_pixels_to_buffer / get_texture_image_to_buffer and waits for nothing - the server lands the rows through the buffer-write gate on both backends, the client marks the buffer GPU-written, and a device lost with the write still owed ends in Fatal{ReadbackDeclined, "buffer-writeback"}

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swung0x48
2026-09-29 02:02:29 -04:00
parent ad705a7392
commit 6485ae1dc0
28 changed files with 1152 additions and 58 deletions
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MobileGL/MG_Remote/Client/EmitTables.cpp
+63 -16
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@@ -861,15 +861,23 @@ namespace MobileGL::MG_Remote::Client {
ReadbackBytesPerPixel(format, type);
}
void ApplyReadbackByteSwap(void* pixels, Uint64 bytes, GLenum type,
const PixelStoreParameters& pack) {
if (!pack.SwapBytes || pixels == nullptr) return;
// GL_PACK_SWAP_BYTES as the width of the byte group it reverses for `type`, 0 when there
// is nothing to reverse. One rule for both places a swap happens: the reply form swaps
// here, and the pack-buffer form (P9) carries the number to the server, which swaps there.
Uint32 ReadbackSwapGroup(GLenum type, const PixelStoreParameters& pack) {
if (!pack.SwapBytes) return 0;
const auto dataType = MG_Util::ConvertGLEnumToTexturePixelDataType(type);
SizeT group = MG_Util::GetSizedTexturePixelDataTypeSize(dataType);
if (group == 0) group = MG_Util::GetBaseTexturePixelDataTypeSize(dataType);
// This packed depth/stencil type contains two independent 32-bit words.
if (type == GL_FLOAT_32_UNSIGNED_INT_24_8_REV) group = 4;
if (group <= 1) return;
return group <= 1 ? 0 : static_cast<Uint32>(group);
}
void ApplyReadbackByteSwap(void* pixels, Uint64 bytes, GLenum type,
const PixelStoreParameters& pack) {
const SizeT group = ReadbackSwapGroup(type, pack);
if (group == 0 || pixels == nullptr) return;
auto* data = static_cast<Uint8*>(pixels);
for (Uint64 at = 0; at + group <= bytes; at += group) {
for (SizeT i = 0; i < group / 2; ++i) {
@@ -963,6 +971,56 @@ namespace MobileGL::MG_Remote::Client {
return;
}
// One band's source record, the same for both destinations below.
const auto bandInfo = [&](const ReadbackBand& band, Uint64 bandBytes) {
MG_Pipe::MGPReadbackInfo info{};
info.Res = MG_Pipe::kMGPipeNullHandle; // "the bound read surface answers"
info.Box = MG_Pipe::MGPBox{ReadbackBandOrigin(x, band.FirstColumn),
ReadbackBandOrigin(y, band.FirstRow), 0,
static_cast<Uint32>(band.Columns),
static_cast<Uint32>(band.Rows), 1};
info.Format = static_cast<Uint32>(format);
info.Type = static_cast<Uint32>(type);
info.Target = 0;
info.Level = 0;
info.DstOffset = 0;
info.DstSize = bandBytes;
return info;
};
// P9 (W1, CONTRACT-P9.md §1): A PACK BUFFER IS ANSWERED BY NOTHING. Each band crosses
// as read_pixels_to_buffer naming the buffer and the band's place in it - the
// layout above, per band - and the client neither waits nor copies: the server lands
// the rows, and the mark (taken first, like every producer row's) is what sends the
// next CPU read of the buffer through resource_readback. The bands are the reply
// form's for the SERVER's sake, not the wire's: the server reads each one into its
// scratch before landing it, and the reply cap is the bound it already enforces on
// that scratch (PH-3). The monolith arm is untouched - it maps the driver PBO back
// inside its own ReadPixels, as it always has.
if (pbo) {
const MG_Pipe::MGPipeHandle target = PackBufferReadbackTarget(pbo, pboOffset + layout.End);
if (!MG_Pipe::MGPipeHandleIsNull(target)) {
MarkReadPixelsPackBuffer();
const Uint32 swapGroup = ReadbackSwapGroup(type, pack);
ForEachReadbackBand(static_cast<Uint64>(width), static_cast<Uint64>(height), plan,
[&](const ReadbackBand& band) {
MG_Pipe::MGPReadbackToBuffer record{};
record.Src = bandInfo(band, TightReadbackBytes(static_cast<GLsizei>(band.Columns),
static_cast<GLsizei>(band.Rows),
format, type));
record.Dst = target;
record.DstBase = pboOffset + layout.Start + band.FirstRow * layout.RowStride +
band.FirstColumn * bytesPerPixel;
record.RowStride = layout.RowStride;
record.ImageStride = 0;
record.SwapGroup = swapGroup;
session.EmitAndWait(MG_Pipe::MGPWireOp::ReadPixelsToBuffer, &record,
sizeof(record), nullptr, 0, nullptr, 0, nullptr);
});
return;
}
}
// THE COMMON CASE KEEPS THE ZERO-COPY. A neutral pack state means the destination
// layout IS the tight layout, so each band's reply lands straight in the
// application's buffer at the band's tight offset (whole-width bands and single-row
@@ -983,18 +1041,7 @@ namespace MobileGL::MG_Remote::Client {
const Uint64 bandBytes = TightReadbackBytes(static_cast<GLsizei>(band.Columns),
static_cast<GLsizei>(band.Rows),
format, type);
MG_Pipe::MGPReadbackInfo info{};
info.Res = MG_Pipe::kMGPipeNullHandle; // "the bound read surface answers"
info.Box = MG_Pipe::MGPBox{ReadbackBandOrigin(x, band.FirstColumn),
ReadbackBandOrigin(y, band.FirstRow), 0,
static_cast<Uint32>(band.Columns),
static_cast<Uint32>(band.Rows), 1};
info.Format = static_cast<Uint32>(format);
info.Type = static_cast<Uint32>(type);
info.Target = 0;
info.Level = 0;
info.DstOffset = 0;
info.DstSize = bandBytes;
MG_Pipe::MGPReadbackInfo info = bandInfo(band, bandBytes);
// CHECKED BEFORE THE EMISSION, not after the answer (ID-47), through S1's
// helper, for every record. The plan makes it true by construction; it stays