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Subject[PATCH v2 3/4] tty: documentation: abi: add ttyvs null modem driver sysfs nodes
The ttyvs driver exposes sysfs file called event to emulate
various serial port events. This commit document this file.
User space application writes various codes to this file.

Signed-off-by: Rishi Gupta <>
Changes in v2:
- Updated path to /sys/class/tty/ttyvsN/event
- Used Documentation/ABI/testing/sysfs-tty, previously new file was created

Documentation/ABI/testing/sysfs-tty | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
index 9eb3c2b..c6002c5 100644
--- a/Documentation/ABI/testing/sysfs-tty
+++ b/Documentation/ABI/testing/sysfs-tty
@@ -154,3 +154,18 @@ Description:
device specification. For example, when user sets 7bytes on
16550A, which has 1/4/8/14 bytes trigger, the RX trigger is
automatically changed to 4 bytes.
+What: /sys/class/tty/ttyvsN/event
+Date: February 2020
+Contact: Rishi Gupta <>
+ The ttyvs driver will emulate serial port event; parity error,
+ framing error, overrun error, asserting/de-asserting break
+ condition and ring indication when user space application
+ writes an event code on this sysfs file.
+ Write 1 to emulate framing error, write 2 for parity error,
+ write 3 for overrun error, write 4 to set ring indication,
+ write 5 to clear ring indication, write 6 to emulate a break
+ condition detected, write 7 to emulate a faulty cable and
+ write 8 to remove faulty cable condition.
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