check out slide 5 here:

http://www.slideshare.net/anil_pugalia/embedded-device-busdrivers

On Wed, Jan 25, 2012 at 9:36 AM, Peter Teoh <htmldeveloper@gmail.com> wrote:
read this:

http://elinux.org/Disable_Console 

and this:

http://elinux.org/Kernel_Debugging_Tips#Controlling_console_output 

Perhaps u can extract relevant APIs from below URLs to solve your problem:

a.   at the hardware level, serial communication can come from UART interface, or infrared interface, or USB.

b.   next, is the 8250.c handler:   
http://lxr.free-electrons.com/source/drivers/tty/serial/8250_*.c (star represent the different hardware devices handling the serial signals).

c.   next all these information will feed into serial_core.c (USB is not included here):

http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c

And here u can see how u can disable the signal from software standpoint, eg, 

In particular:
 78 static void uart_stop(struct tty_struct *tty)
 79 {
 80         struct uart_state *state = tty->driver_data;
 81         struct uart_port *port = state->uart_port;
 82         unsigned long flags;
 83 
 84         spin_lock_irqsave(&port->lock, flags);
 85         port->ops->stop_tx(port);
 86         spin_unlock_irqrestore(&port->lock, flags);
 87 }
 88
From above, u can see stop_tx() can be called, looking further into 8250.c:


static void serial8250_stop_tx(struct uart_port *port)
{


        struct uart_8250_port *up =
                container_of(port, struct uart_8250_port, port);




        __stop_tx(up);



        /*


         * We really want to stop the transmitter from sending.
         */



        if (up->port.type == PORT_16C950) {
                up->acr |= UART_ACR_TXDIS;



                serial_icr_write(up, UART_ACR, up->acr);
        }



}


And referring further to definition:



/*
 * The 16C950 Additional Control Register



 */
#define UART_ACR_RXDIS  0x01    /* Receiver disable */


#define UART_ACR_TXDIS  0x02    /* Transmitter disable */



So perhaps writing UART_ACR_XXX_DIS will disable the input/output:




drivers/tty/serial/8250.c:		up->acr |= UART_ACR_TXDIS;



drivers/tty/serial/8250.c:		up->acr &= ~UART_ACR_TXDIS;




Experiment first....I am just guessing....


On Wed, Jan 4, 2012 at 8:43 AM, hz hanks <hankshz@gmail.com> wrote:
Hi, all~
I'm studying in an embedded Linux board with only one uart, which is
set default as the console display. Now as I try to develop uart
driver, I want to shutdown this console redirection temporarily. But I
don't know how? I search the Internet, but there's only the tutorial
for setting this redirection rather than shutdown it. Is there anyone
can help? Thank you very much.

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--
Regards,
Peter Teoh



--
Regards,
Peter Teoh