From: Adam Simonelli <adamsimonelli@xxxxxxxxx>
When switching to a CONFIG_VT=n world, at least on x86 systems,
/dev/console becomes /dev/ttyS0. This can cause some undesired effects.
/dev/console's behavior is now tied to the physical /dev/ttyS0, which when
disconnected can cause isatty() to fail when /dev/ttyS0 is disconnected,
and users who upgrade to a theoretical vt-less kernel from their
distribution who have a device such as a science instrument connected to
their /dev/ttyS0 port will suddenly see it receive kernel log messages.
When the new CONFIG_NULL_TTY_CONSOLE option is turned on, this will allow
the ttynull device to be leveraged as the default console. Distributions
that had CONFIG_VT turned on before will be able to leverage this option
to where /dev/console is still backed by a psuedo device, avoiding these
issues, without needing to enable the entire VT subsystem.
v2:
rebase
v3:
Clarify commit messages.
Guard the all the register_console()s in ttynull to prevent it from being
registered twice.
Only change the link order if CONFIG_NULL_TTY_CONSOLE is enabled, otherwise
use the existing order for ttynull if only CONFIG_NULL_TTY is enabled.
Document why the link order changes in the drivers/tty/Makefile file.
Replace #ifdefs
v4:
Remember to actually include the changes to v3 in the cover letter.
v5:
Correct code formatting in Makefile comment.
Adam Simonelli (2):
ttynull: Add an option to allow ttynull to be used as a console device
tty: Change order of ttynull to be linked sooner if enabled as a
console.
drivers/tty/Kconfig | 15 ++++++++++++++-
drivers/tty/Makefile | 10 ++++++++++
drivers/tty/ttynull.c | 20 +++++++++++++++++++-
3 files changed, 43 insertions(+), 2 deletions(-)
--
2.45.2
