Serial console not accepting input

Gerard Basler gbasler at
Sat Mar 23 21:00:40 EST 2002


This seems to be the same problem we had same days ago.
First the shell didn't start because we hadn't turned FPU emulation on.
Then the shell started but we couldn't see any reaction on the typed
Which root filesystem do you use?
We used an old root filesystem from Montavista.
Because this was rather old we cross-compiled several packages from and tested them.
Replacing the old "/sbin/init" with a newer version solved this problem
(statically linked).
Download it from here:

Perhaps someone has an explanation for this!
What has changed in newever kernels?


On Fri, 22 Mar 2002, Ho-Kuo Chan wrote:

> Hi,
>     I have managed to get kernel 2-4-19-pre3 booting on my PPC405 GP based
> custom board (which is based on the Walnut). The problem is that the serial
> console does not accept any input. When I say this I mean the typed
> characters are receievd but ignored. I know this because I turned on the
> SERIAL_DEBUG_INTR flag on and the chars are received. I then traced the code
> to find that in receive_chars in drivers/char/serial.c, the chars are only
> accepted if the ignore_status_mask does not have the recieve buffer not
> empty bit set. Well the ignore_status_mask is set in the function
> change_speed if the cflag variable is not equal to CREAD:
> if ((cflag & CREAD) == 0)
>     info->ignore_status_mask |= UART_LSR_DR;
> The cflag is equal to the tty's termios.c_cflag which I believe is set to
> the serial console driver's cflag. I checked the sercons.cflag and it is
> originally set to CREAD | HUPCL | CLOCAL in serial_console_setup called when
> the driver is registered in register_console via serial_console_init.
> However, the sercons.cflag is set to 0 in rs_open() in drivers/serial.c
> which is called when tty_open is called. tty_open is called several times
> during the boot process and as such, results in the ignore_status_mask being
> set, causing the console to ignore input chars. So my question in all of
> this is: why is the sercons.cflag set to 0 in rs_open?
> Thanks in advance!!!
> Ho-Kuo Chan

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