Always allocate per-file can_reader on open so write-only descriptors get msgalign / ioctl state; free that context on close when it was never linked into cd_readers (fixes leak).
Cap each drain loop (20×500 ms) so close() cannot block forever when bxCAN retries without ACK or dev_txempty never clears.
Fix stm32can_vputreg debug log to print the written value (correct parameter name).
Signed-off-by: Alexey Matveev <tippet@yandex.ru>
369755d00b