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drivers/serial: Modify serial/pty to allow NSH/Telnet line edit #19499

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Merged
xiaoxiang781216 merged 1 commit into from
Jul 22, 2026
+131 −23
Merged

drivers/serial: Modify serial/pty to allow NSH/Telnet line edit #19499

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70 changes: 58 additions & 12 deletions drivers/serial/pty.c
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,20 @@
* Pre-processor Definitions
****************************************************************************/

/* States for the local-echo VT100/ANSI escape sequence detector used by
* pty_read() below (dev->pd_escape). This mirrors the equivalent state
* machine in drivers/serial/serial.c (uart_readv()) -- see the comment
* there for the full rationale. It does not interpret the sequence, it
* only decides how many bytes to swallow from the local echo; the
* sequence bytes themselves are still delivered to the reader
* unmodified either way.
*/

#define UART_ESCAPE_NONE 0 /* Not in an escape sequence */
#define UART_ESCAPE_START 1 /* Saw ESC, waiting for '[', 'O', or other */
#define UART_ESCAPE_CSI 2 /* Saw "ESC [", consuming CSI bytes */
#define UART_ESCAPE_SS3 3 /* Saw "ESC O", waiting for the final byte */

/* Maximum number of threads than can be waiting for POLL events */

#ifndef CONFIG_DEV_PTY_NPOLLWAITERS
Expand All @@ -80,7 +94,10 @@ struct pty_dev_s
struct file pd_src; /* Provides data to read() method (pipe output) */
struct file pd_sink; /* Accepts data from write() method (pipe input) */
bool pd_master; /* True: this is the master */
uint8_t pd_escape; /* Number of the character to be escaped */
uint8_t pd_escape; /* Escape sequence echo-suppression state
* (see the UART_ESCAPE_* values used in
* pty_read())
*/
#if defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGTSTP)
pid_t pd_pid; /* Thread PID to receive signals (-1 if none) */
#endif
Expand Down Expand Up @@ -480,29 +497,58 @@ static ssize_t pty_read(FAR struct file *filep, FAR char *buffer, size_t len)
{
ch = buffer[i];

/* Check for the beginning of a VT100 escape sequence, 3 byte */
/* Detect a VT100/ANSI escape sequence (CSI "ESC [ ... <final>"
* or SS3 "ESC O <final>") so it can be swallowed from the
* local echo below. See the UART_ESCAPE_* comment above.
*/

if (ch == ASCII_ESC)
{
/* Mark that we should skip 2 more bytes */

dev->pd_escape = 2;
dev->pd_escape = UART_ESCAPE_START;
continue;
}
else if (dev->pd_escape == 2 && ch != ASCII_LBRACKET)
else if (dev->pd_escape == UART_ESCAPE_START)
{
/* It's not an <esc>[x 3 byte sequence, show it */
if (ch == ASCII_LBRACKET)
{
dev->pd_escape = UART_ESCAPE_CSI;
continue;
}
else if (ch == ASCII_O)
{
dev->pd_escape = UART_ESCAPE_SS3;
continue;
}

/* Not CSI or SS3 -- an unrecognized two-byte "ESC x"
* sequence. Fall through and consider 'x' for the echo
* batch normally, as before.
*/

dev->pd_escape = 0;
dev->pd_escape = UART_ESCAPE_NONE;
}
else if (dev->pd_escape > 0)
else if (dev->pd_escape == UART_ESCAPE_CSI)
{
/* Skipping character count down */
/* Consuming CSI parameter/intermediate bytes (0x20-0x3f);
* the sequence ends with exactly one final byte in
* 0x40-0x7e.
*/

if (--dev->pd_escape > 0)
if (ch >= 0x40 && ch <= 0x7e)
{
continue;
dev->pd_escape = UART_ESCAPE_NONE;
}

continue;
}
else if (dev->pd_escape == UART_ESCAPE_SS3)
{
/* The byte following "ESC O" is always the final (and
* only) byte.
*/

dev->pd_escape = UART_ESCAPE_NONE;
continue;
}

/* Echo if the character in batch */
Expand Down
78 changes: 68 additions & 10 deletions drivers/serial/serial.c
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,32 @@

#define POLL_DELAY_USEC 1000

/* States for the local-echo VT100/ANSI escape sequence detector used by
* uart_readv() below (dev->escape). This does not interpret the
* sequence, it only decides how many bytes to swallow from the local
* echo so that raw escape sequences typed by the user are not rendered
* as visible garbage; the sequence bytes themselves are still delivered
* to the reader unmodified either way.
*
* Two forms are recognized:
*
* CSI: ESC '[' <zero or more parameter/intermediate bytes, 0x20-0x3f>
* <one final byte, 0x40-0x7e>
* e.g. ESC[D (left arrow), ESC[3~ (Delete), ESC[1;5D (Ctrl+Left)
*
* SS3: ESC 'O' <one final byte>
* e.g. ESC O F (End, as sent by xterm and many other terminals
* that otherwise use CSI for the plain arrow keys)
*
* Any other byte following ESC is treated as an unrecognized two-byte
* "ESC x" sequence; 'x' itself is echoed normally, as before.
*/

#define UART_ESCAPE_NONE 0 /* Not in an escape sequence */
#define UART_ESCAPE_START 1 /* Saw ESC, waiting for '[', 'O', or other */
#define UART_ESCAPE_CSI 2 /* Saw "ESC [", consuming CSI bytes */
#define UART_ESCAPE_SS3 3 /* Saw "ESC O", waiting for the final byte */

/****************************************************************************
* Private Types
****************************************************************************/
Expand Down Expand Up @@ -1063,26 +1089,58 @@ static ssize_t uart_readv(FAR struct file *filep, FAR struct uio *uio)

if (dev->tc_lflag & ECHO)
{
/* Check for the beginning of a VT100 escape sequence, 3 byte */

if (ch == ASCII_ESC)
{
/* Mark that we should skip 2 more bytes */
/* Start (or restart) tracking a possible escape
* sequence.
*/

dev->escape = 2;
dev->escape = UART_ESCAPE_START;
continue;
}
else if (dev->escape == 2 && ch != ASCII_LBRACKET)
else if (dev->escape == UART_ESCAPE_START)
{
/* First byte after ESC selects the sequence type */

if (ch == ASCII_LBRACKET)
{
dev->escape = UART_ESCAPE_CSI;
continue;
}
else if (ch == ASCII_O)
{
dev->escape = UART_ESCAPE_SS3;
continue;
}

/* Not CSI or SS3 -- an unrecognized two-byte "ESC x"
* sequence. Fall through and echo 'x' normally, as
* before.
*/

dev->escape = UART_ESCAPE_NONE;
}
else if (dev->escape == UART_ESCAPE_CSI)
{
/* It's not an <esc>[x 3 byte sequence, show it */
/* Consuming CSI parameter/intermediate bytes
* (0x20-0x3f); the sequence ends with exactly one
* final byte in 0x40-0x7e.
*/

if (ch >= 0x40 && ch <= 0x7e)
{
dev->escape = UART_ESCAPE_NONE;
}

dev->escape = 0;
continue;
}
else if (dev->escape > 0)
else if (dev->escape == UART_ESCAPE_SS3)
{
/* Skipping character count down */
/* The byte following "ESC O" is always the final
* (and only) byte.
*/

dev->escape--;
dev->escape = UART_ESCAPE_NONE;
continue;
}

Expand Down
6 changes: 5 additions & 1 deletion include/nuttx/serial/serial.h
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Original file line number Diff line number Diff line change
Expand Up @@ -326,7 +326,11 @@ struct uart_dev_s
/* State data */

uint8_t open_count; /* Number of times the device has been opened */
uint8_t escape; /* Number of the character to be escaped */
uint8_t escape; /* VT100/ANSI escape sequence echo-
* suppression state (see the
* UART_ESCAPE_* values used in
* uart_readv())
*/
#ifdef CONFIG_SERIAL_REMOVABLE
volatile bool disconnected; /* true: Removable device is not connected */
#endif
Expand Down
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