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My terminal has 4 Serial ports. I try to find them with command dmesg | grep tty. This is what I get:

[ 1.317597] serial8250: ttyS2 at I/O 0x3e8 (irq = 4) is a 16550A
[    1.317730] serial8250: ttyS3 at I/O 0x2e8 (irq = 3) is a 16550A
[    1.319571] 00:0c: ttyS3 at I/O 0x2e8 (irq = 4) is a 16550A
[    1.319799] 00:0d: ttyS2 at I/O 0x3e8 (irq = 3) is a 16550A
[    1.320007] 00:0e: ttyS2 at I/O 0x3e8 (irq = 4) is a 16550A
[    1.320213] 00:0f: ttyS3 at I/O 0x2e8 (irq = 3) is a 16550A

So I find only ttyS2 and ttyS3 ...

And when I try the command setserial -g /dev/ttyS* I get this result:

/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: 16550A, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: 16550A, Port: 0x02e8, IRQ: 3`

Why aren't the serial ports ttyS0 and ttyS1 listed in "dmesg"?

  • Your dmesg may be truncated because of the kernel buffer limit. You may increase it with the log_buf_len=n kernel boot parameter. What does dmesg | head -n10 show? – pizdelect Apr 20 at 15:19
  • 'dmesg | head -n10 [] Initializing cgroup subsys cpuset [] Initializing cgroup subsys cpu [] Linux version 2.6.35.13 (xxx@xxx) (gcc version 4.4.5 (Debian 4.4.5-8) ) #1 SMP Tue May 3 10:17:59 CEST 2011 []BIOS-provided physical RAM map: []BIOS-e820: 0000000000000000-000000000009fc00 (usable) []BIOS-e820: 000000000009fc00-00000000000a0000 (reserved) []BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) []BIOS-e820: 0000000000100000 - 000000007fda0000 (usable) []BIOS-e820: 000000007fda0000 - 000000007fdae000 (ACPI data) []BIOS-e820: 000000007fdae000 - 000000007fde0000 (ACPI NVS) ' – Prashant Sharma Apr 22 at 8:16
  • Can anyone help me to resolve the below issue ? – Prashant Sharma Apr 24 at 5:45

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