On Thu, Sep 05, 2024 at 03:53:18PM +0206, John Ogness wrote:
> Implement the necessary callbacks to switch the 8250 console driver
> to perform as an nbcon console.
>
> Add implementations for the nbcon console callbacks (write_atomic,
> write_thread, device_lock, device_unlock) and add CON_NBCON to the
> initial flags.
>
> The legacy code is kept in order to easily switch back to legacy mode
> by defining USE_SERIAL_8250_LEGACY_CONSOLE.
...
> static struct console univ8250_console = {
> .name = "ttyS",
> +#ifdef USE_SERIAL_8250_LEGACY_CONSOLE
Can it be done at run-time (theoretically or even practically)?
(Note that we have already knob to disable / enable consoles.)
> .write = univ8250_console_write,
> + .flags = CON_PRINTBUFFER | CON_ANYTIME,
> +#else
> + .write_atomic = univ8250_console_write_atomic,
> + .write_thread = univ8250_console_write_thread,
> + .device_lock = univ8250_console_device_lock,
> + .device_unlock = univ8250_console_device_unlock,
> + .flags = CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON,
> +#endif
> .device = uart_console_device,
> .setup = univ8250_console_setup,
> .exit = univ8250_console_exit,
> .match = univ8250_console_match,
> - .flags = CON_PRINTBUFFER | CON_ANYTIME,
> .index = -1,
> .data = &serial8250_reg,
> };
I would arrange this slightly differently, but not a big deal.
static struct console univ8250_console = {
.name = "ttyS",
.device = uart_console_device,
#ifndef USE_SERIAL_8250_LEGACY_CONSOLE
.flags = CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON,
.write_atomic = univ8250_console_write_atomic,
.write_thread = univ8250_console_write_thread,
.device_lock = univ8250_console_device_lock,
.device_unlock = univ8250_console_device_unlock,
#else
.flags = CON_PRINTBUFFER | CON_ANYTIME,
.write = univ8250_console_write,
#endif
.setup = univ8250_console_setup,
.exit = univ8250_console_exit,
.match = univ8250_console_match,
.index = -1,
.data = &serial8250_reg,
};
...
> + if (nbcon_exit_unsafe(wctxt)) {
> + int len = READ_ONCE(wctxt->len);
> + int i;
unsigned ?
> + /*
> + * Write out the message. Toggle unsafe for each byte in order
> + * to give another (higher priority) context the opportunity
> + * for a friendly takeover. If such a takeover occurs, this
> + * must abort writing since wctxt->outbuf and wctxt->len are
> + * no longer valid.
> + */
> + for (i = 0; i < len; i++) {
> + if (!nbcon_enter_unsafe(wctxt))
> + break;
> +
> + uart_console_write(port, wctxt->outbuf + i, 1, serial8250_console_putchar);
> +
> + if (!nbcon_exit_unsafe(wctxt))
> + break;
> + }
> + }
...
> + /* Finally, wait for transmitter to become empty and restore IER. */
> + wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
> + if (em485) {
> + mdelay(port->rs485.delay_rts_after_send);
> + if (em485->tx_stopped)
> + up->rs485_stop_tx(up);
> + }
> + serial_port_out(port, UART_IER, ier);
> +
> + /*
> + * The receive handling will happen properly because the receive ready
> + * bit will still be set; it is not cleared on read. However, modem
> + * control will not, we must call it if we have saved something in the
> + * saved flags while processing with interrupts off.
> + */
> + if (up->msr_saved_flags)
> + serial8250_modem_status(up);
(1)
...
> + /* Atomic console not supported for rs485 mode. */
RS485
...
> + /*
> + * First save IER then disable the interrupts. The special variant to
> + * clear IER is used because atomic printing may occur without holding
> + * the port lock.
> + */
> + ier = serial_port_in(port, UART_IER);
> + __serial8250_clear_IER(up);
> +
> + /* Check scratch reg if port powered off during system sleep. */
> + if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
> + serial8250_console_restore(up);
> + up->canary = 0;
> + }
> +
> + if (up->console_newline_needed)
> + uart_console_write(port, "\n", 1, serial8250_console_putchar);
> + uart_console_write(port, wctxt->outbuf, wctxt->len, serial8250_console_putchar);
> +
> + /* Finally, wait for transmitter to become empty and restore IER. */
> + wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
> + serial_port_out(port, UART_IER, ier);
(2)
Feels like parts (1) and (2) duplicates existing pieces of code. May it be
refactored to minimize the duplication?
--
With Best Regards,
Andy Shevchenko
