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arch/sim: don't block on the wrapped RX segment of the simulated UART #20028

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arch/sim: don't block on the wrapped RX segment of the simulated UART #20028

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arch/sim: don't block on the wrapped RX segment of the simulated UART
raiden00pl Aug 31, 2026
cf9c69e
arch/sim/sim_uart.c: fix nxstyle errors
raiden00pl Sep 1, 2026
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9 changes: 8 additions & 1 deletion arch/sim/src/sim/sim_uart.c
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Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,7 @@ static void uart_nputs(int fd, const char *buf, size_t size)
while (size > 0)
{
int ret = host_uart_puts(fd, buf, size);

if (ret < 0)
{
continue;
Expand Down Expand Up @@ -622,7 +623,12 @@ static void tty_dmareceive(struct uart_dev_s *dev)
{
xfer->nbytes = ret;

if (ret == xfer->length && xfer->nlength > 0)
/* The console fd is blocking, so only continue into the wrapped

@xiaoxiang781216 xiaoxiang781216 Sep 1, 2026

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should we change fd to the non-blocking mode

@raiden00pl raiden00pl Sep 1, 2026

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changing to non-blocking requires rework of more logic, this is the minimal correct fix.

@xiaoxiang781216 xiaoxiang781216 Sep 1, 2026

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but the code should work with non-block mode already:
https://github.com/apache/nuttx/blob/master/arch/sim/src/sim/posix/sim_hostuart.c#L119

@raiden00pl raiden00pl Sep 1, 2026

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uart_nputs() won't work well with it. Simulated uarts never execute this path, sim console fd is always forced to host fd=0.

Another thing is that we will change default host fd 0 setting (we have to call fcntl(0, F_SETFL, O_NONBLOCK) ) which we should recover after nuttx simulator is closed or crash.

This fix is ​​a one-line fix, changing it to NONBLOCK is a rebuild of how the sim console works.

@xiaoxiang781216 xiaoxiang781216 Sep 1, 2026

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uart_nputs() won't work well with it. Simulated uarts never execute this path, sim console fd is always forced to host fd=0.

Another thing is that we will change default host fd 0 setting (we have to call fcntl(0, F_SETFL, O_NONBLOCK) )

yes, here is the change: #20032
we use internally more than half year without problem.

which we should recover after nuttx simulator is closed or crash.

why need? non-block is the property of file handle, not the terminal.

This fix is ​​a one-line fix, changing it to NONBLOCK is a rebuild of how the sim console works.

* part of the circular buffer if there is really more data.
*/

if (ret == xfer->length && xfer->nlength > 0 &&
host_uart_checkin(priv->fd))
{
ret = host_uart_gets(priv->fd, xfer->nbuffer, xfer->nlength);
if (ret > 0)
Expand Down Expand Up @@ -800,6 +806,7 @@ void up_putc(int ch)
{
#ifdef USE_DEVCONSOLE
char c = ch;

up_nputs(&c, 1);
#endif
}
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