Hi, While booting v5.5-rc1 on Apollo Lake based UP2[0], I ran into an issue with the primary serial port. The kernel is able to output to ttyS0 but systemd isn't able to raise a login prompt. On further investigation, it turns out that no serial device (/dev/ttyS0) is being created as the device is claimed by serdev sub-system. The issue has been reported in a few different places[0][1]. A patch was proposed to solve the issue but there doesn't seem to be any further progress[2]. Feedback on the thread suggested implementing a whitelist based approach - which is what this RFC does. With this patch, systemd is able to create a login prompt. The whitelist has intentionally been left blank as it's not clear which devices go in there. Feedback welcome. Thanks, Punit [0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=911831 [1] https://bugs.launchpad.net/ubuntu/+source/linux-oem/+bug/1769610 [2] https://marc.info/?l=linux-serial&m=152455861101408&w=2 Punit Agrawal (1): serdev: Only claim supported devices drivers/tty/serdev/core.c | 8 ++++++++ 1 file changed, 8 insertions(+) -- 2.24.0
