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I have an embedded Linux system (i.e just Busybox) with a framebuffer (/dev/fb0) and a serial port (/dev/hvc0). The serial port is the only method of console input currently.

My Kernel has;

CONFIG_FB=y
CONFIG_FB_SIMPLE=y
CONFIG_VGA_CONSOLE=y
CONFIG_DUMMY_CONSOLE=y
CONFIG_DUMMY_CONSOLE_COLUMNS=80
CONFIG_DUMMY_CONSOLE_ROWS=25
CONFIG_FRAMEBUFFER_CONSOLE=y
CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY=y

My bootargs are currently;

bootargs = "console=hvc0 earlycon=sbi debug";

What I would like to do is use the frame-buffer to display the console output (login terminal, printk output), but with input coming from the serial port (/dev/hvc0).

ultraembedded
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    I dunno kernel has such possibility out-of-the-box. But you may establish full console on FB device, just run any type of `getty` and you are all set. Yes, it will require some input device, like keyboard. – 0andriy Aug 09 '20 at 10:22

1 Answers1

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Can you be more specific regarding the Hw and the OS and u-boot? You need something like this:

setenv bootargs console=ttyO2,115200n8 vram=16M root=/dev/ram0 rw ramdisk_size=16384 initrd=0x83000000,16M rootfstype=ext2 or this: setenv bootargs 'console=ttymxc0,115200 root=/dev/mmcblk2p1 rootwait rw video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24'

You see, you need to specify the tty = serial port configuration (speed, parity and so on). Also the type of file system ext2, ext4, ... the above are just examples and you need to base yours according to your system.

Sebastian Moreno
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  • I left these details out as they complicate the question somewhat! The HW is my own design (RISC-V CPU, serial port, SoC), the bootloader is also my own (bootargs come from the DTS file). I do not need a lot of the arguments you mentioned. I'm really just trying to understand more about the interactions of fbcon and tty consoles. – ultraembedded Aug 08 '20 at 09:36