Hi, Valdis,
Yes, I understand shell is a user program.
I just added some uart print to see what's happening. (while trying to open a shell on LCD using USB keyboard..)
When I see it n fbcon_scroll function(one of console switch functions which connect to bit blit functions)(in drivers/video/console/fbcon.c) while some printks are scrolled up on the LCD, the vc_data is using tty null (vc->port.tty->name is null) then at some point changes to tty1. This is even when I set "console=tty0 " in the boot argument. When I set "console=tty1 ", it's the same. This is when I remvoed /etc/inittab file so that defulat inittab is put in place by busybox... I understand busybox init starts shells on tty2,tty3,and tty4. So the output is using tty1.
In input side, when I use print (to uart) on kbd_keycoad function(drivers/tty/vt/keyboard.c), and press any key, I can see the vc->port.tty->name is tty1. (vc is of type vc_data). So the input is connected to tty1 (same as output). But I don't see any change on the LCD at that state (as I press the keyboard).
Any idea? any suggestion will be appreciated. I don't know how to assign tty and how to make the fbconsole(or vc on it) to appear on the LCD so to speak.
regards,
Chan

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From : "Valdis.Kletnieks at vt.edu" [off-list ref]

Sent : 2014-03-12 21:14:49 ( +09:00 )
To : Kim Chan [off-list ref]
Cc : Kernel [off-list ref], kernelnewbies at kernelnewbies.org [off-list ref]
Subject : Re: Does register_chrdev function make device file under /dev ?

On Tue, 11 Mar 2014 08:01:26 -0000, Kim Chan said:

To my understanding, device file is needed when a user program wants to
access the device and we don't need to generate the device file for us to use
the device in kernel. Is my understanding correct?

Right. You don't need to generate the device file because you shouldn't be
accessing the device in a file-like manner from inside the kernel.

I am trying to open a shell on my LCD (is it going to be tty2

That's userspace, not kernel access.
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