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 <[email protected]> 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/<http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c>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 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L78> > static void uart_stop > <http://lxr.free-electrons.com/ident?i=uart_stop>(struct tty_struct > <http://lxr.free-electrons.com/ident?i=tty_struct> *tty > <http://lxr.free-electrons.com/ident?i=tty>) > 79 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L79> { > 80 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L80> > struct uart_state <http://lxr.free-electrons.com/ident?i=uart_state> > *state <http://lxr.free-electrons.com/ident?i=state> = tty > <http://lxr.free-electrons.com/ident?i=tty>->driver_data > <http://lxr.free-electrons.com/ident?i=driver_data>; > 81 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L81> > struct uart_port <http://lxr.free-electrons.com/ident?i=uart_port> > *port <http://lxr.free-electrons.com/ident?i=port> = state > <http://lxr.free-electrons.com/ident?i=state>->uart_port > <http://lxr.free-electrons.com/ident?i=uart_port>; > 82 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L82> > unsigned long flags <http://lxr.free-electrons.com/ident?i=flags>; > 83 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L83> > 84 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L84> > spin_lock_irqsave > <http://lxr.free-electrons.com/ident?i=spin_lock_irqsave>(&port > <http://lxr.free-electrons.com/ident?i=port>->lock > <http://lxr.free-electrons.com/ident?i=lock>, flags > <http://lxr.free-electrons.com/ident?i=flags>); > 85 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L85> > port <http://lxr.free-electrons.com/ident?i=port>->ops > <http://lxr.free-electrons.com/ident?i=ops>->stop_tx(port > <http://lxr.free-electrons.com/ident?i=port>); > 86 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L86> > spin_unlock_irqrestore > <http://lxr.free-electrons.com/ident?i=spin_unlock_irqrestore>(&port > <http://lxr.free-electrons.com/ident?i=port>->lock > <http://lxr.free-electrons.com/ident?i=lock>, flags > <http://lxr.free-electrons.com/ident?i=flags>); > 87 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L87> } > 88 > <http://lxr.free-electrons.com/source/drivers/tty/serial/serial_core.c#L88> > > 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 <[email protected]> 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. >> >> _______________________________________________ >> Kernelnewbies mailing list >> [email protected] >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > > > > -- > Regards, > Peter Teoh > -- Regards, Peter Teoh
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