bq27441: Fix checksum overflow in compute_block_checksum().#161
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nedseb
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Pull request overview
Fixes a bug in compute_block_checksum() where the sum of 32 data bytes could exceed 255, causing a negative checksum value and a ValueError when writing to the register. The fix masks the sum to a single byte before computing the complement.
Changes:
- Mask the intermediate checksum sum to 8 bits before subtracting from 255, preventing negative/out-of-range values.
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Closes #162
Summary
Fix a pre-existing bug where
compute_block_checksum()could produce a negative value when the sum of the 32 data bytes exceeds 255. This causedValueError: bytes value out of rangein_write_reg()during__init__→power_on()→set_capacity()→write_extended_data().Root cause
Fix
This bug has existed since the initial driver commit but only manifests on real hardware (mock I2C returns zeroed data that stays within range).
Test plan
Mock tests
Hardware tests