Lab 3 tasks

Work in labs/kbd/. Build a reliable keyboard layer before application behavior, and keep controller reads, parser state, and output separate.

Requested functions

• int kbc_read_status(uint8_t *status)
• int kbc_read_output(uint8_t *byte)
• int kbc_write_command(uint8_t command)
• int kbd_process_byte(uint8_t byte)
• int kbd_get_scancode(uint8_t bytes[2], uint8_t *size, int *make)

Guided gaps

Check output pointers, ignore reads without data, detect error bits, store a pending 0xE0 prefix, and report make/break state without losing bytes. Keep command and ACK handling separate from parsing, because a response is not a key event.

Decide how callers observe "no complete scancode yet." It may mean the parser is waiting for the second byte of an extended sequence, not that an error occurred.

IMPORTANT

Do not treat every byte as a complete scancode. Extended scancodes must be assembled before the API reports an event.

Common mistakes

Clearing parser state too early, reporting a scancode before all bytes arrive, treating break codes as presses, and reading output without checking status. Most are ownership mistakes: the program loses track of the next byte, parser state, or subscribed IRQ.

Next: checks and references.