Coding style

The tree is self-consistent; match it.

C

• C11 (-std=gnu11), 4-space indent, K&R braces, no tabs in .c/.h.
• Types: the kernel's fixed-width set (u8/u16/u32/u64/s8/..., types.h) - not uint8_t spellings.
• One declaration per line where the type matters; initialize what you can.
• Every file opens with the SPDX + copyright comment block and a Purpose paragraph that says WHY the file exists. Future readers (and the docs generator) rely on it.
• Function comments: contract, arguments, return codes - especially every negative return.
• Error handling: check, report with a clear message, and unwind - never leak a half-initialized device registration.

Assembly

• .S files (preprocessed): boot.S and the arch trampolines are the reference. Comment the ABI at every entry point.

Shell commands

• Register with shell_register_command_ex + the work-package tag so help -w stays truthful.
• One-line help, usage: printout on argument errors, exit non-zero on failure.
• ASCII only.

Naming

• Files: kernel/<area>/core_<thing>.c, drivers/<bus>/driver_<hw>.c, shell/shell_cmds_<domain>.c, fs/fs_<fs>.c - the tree's layout IS the taxonomy (the docs generator groups by it).
• Symbols: <module>_<verb>_<object> (e.g. driver_block_flush, klog_write, ota_ab_install). Static helpers stay file-local.
• All-caps constants with a module prefix (OC_MB2_TAG_END, SHELL_MAX_COMMANDS).

Limits are part of the design

When you add a bounded table, the limit constant carries a comment explaining the number (see SHELL_MAX_COMMANDS in shell.h - the history of 232->256 is documented at the definition). Keep that discipline: the next person tuning it needs the story.

What not to do

• No dead code "for later" - delete it; git remembers.
• No silent truncation - refuse with a message (alias values are the model: stored in full or refused).
• No // TODO without a BUG- number or a work-package reference.
• No new third-party code: the tree is original, Apache 2.0, and stays that way.