Fix SpiAdapter.Read buffer length mismatch in Mcp23xxx TransferFullDuplex#2492
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Fix SpiAdapter.Read buffer length mismatch in Mcp23xxx TransferFullDuplex#2492Copilot wants to merge 3 commits into
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TransferFullDuplex requires writeBuffer and readBuffer to have the same length. The Read method was creating a 2-byte writeBuffer and a (buffer.Length + 2)-byte readBuffer, causing ArgumentException on real SPI devices. Fix: allocate writeBuffer with the same size as readBuffer, placing OpCode and register address in the first two bytes (remaining bytes are don't-care for the SPI read operation). Also fix the test mock's TransferFullDuplex to only pass command bytes to Write, preventing don't-care padding from corrupting register data. Agent-Logs-Url: https://github.com/dotnet/iot/sessions/7c410060-a096-49b1-8cfa-348f86e1f77b Co-authored-by: krwq <660048+krwq@users.noreply.github.com>
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[WIP] Fix System.ArgumentException for buffer length mismatch
Fix SpiAdapter.Read buffer length mismatch in Mcp23xxx TransferFullDuplex
Apr 9, 2026
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May 14, 2026
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This needs to be re-done with copilot CLI, doesn't seem correct
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Allocate writeBuffer at the same length as readBuffer (buffer.Length + 2) with OpCode and register address in the first 2 bytes. This matches the pattern used in Mcp25xxx and fixes the ArgumentException thrown by UnixSpiDevice.TransferFullDuplex when buffers differ in length. Update the test mock's TransferFullDuplex to only forward the 2-byte command prefix (OpCode + RegisterAddress) to Write, since remaining bytes in the padded writeBuffer are don't-care and should not be written to mock registers. Agent-Logs-Url: https://github.com/dotnet/iot/sessions/16e97003-0f85-4e18-86ab-2bd7516ebc6b Co-authored-by: krwq <660048+krwq@users.noreply.github.com>
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Redone in 4c08fff. Removed the Warning Firewall rules blocked me from connecting to one or more addresses (expand for details)I tried to connect to the following addresses, but was blocked by firewall rules:
If you need me to access, download, or install something from one of these locations, you can either:
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SpiAdapter.Read()to allocate equal-lengthwriteBufferandreadBufferforTransferFullDuplex(matching the Mcp25xxx pattern)SpiDeviceMock.TransferFullDuplexto only forward the 2-byte command prefix toWrite