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-rw-r--r--Documentation/ABI/testing/sysfs-tty16
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
index ad22fb0ee765..9eb3c2b6b040 100644
--- a/Documentation/ABI/testing/sysfs-tty
+++ b/Documentation/ABI/testing/sysfs-tty
@@ -138,3 +138,19 @@ Description:
These sysfs values expose the TIOCGSERIAL interface via
sysfs rather than via ioctls.
+
+What: /sys/class/tty/ttyS0/rx_trig_bytes
+Date: May 2014
+Contact: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
+Description:
+ Shows current RX interrupt trigger bytes or sets the
+ user specified value to change it for the FIFO buffer.
+ Users can show or set this value regardless of opening the
+ serial device file or not.
+
+ The RX trigger can be set one of four kinds of values for UART
+ serials. When users input a meaning less value to this I/F,
+ the RX trigger is changed to the nearest lower value for the
+ 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.