mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-09-11 12:34:43 -04:00
d353934702
Implement the necessary callbacks to switch the 8250 console driver to perform as an nbcon console. Add implementations for the nbcon console callbacks: ->write_atomic() ->write_thread() ->device_lock() ->device_unlock() and add CON_NBCON to the initial @flags. All hardware access in the callbacks is within unsafe sections. The ->write_atomic() and ->write_thread() callbacks allow safe handover/takeover per byte and add a preceding newline if they take over from another context mid-line. For the ->write_atomic() callback, a new irq_work is used to defer modem control since it may be called from a context that does not allow waking up tasks. During suspend/resume the irq_work is not used as this has been shown to cause suspend problems for some hardware. Upon resume, any pending modem control is performed. Note: A new __serial8250_clear_IER() is introduced for direct clearing of UART_IER during console writing (which will not be holding the port lock for atomic printing or KDB/KGDB). This allows restoring a lockdep check to serial8250_clear_IER() in a follow-up commit. Signed-off-by: John Ogness <john.ogness@linutronix.de> Link: https://patch.msgid.link/20260729120439.281252-2-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>