nixpkgs/pkgs/development/python-modules/pyserial/001-rfc2217-only-negotiate-on-value-change.patch

From c8b35f4b871d00e3020f525425517548bed9f6ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
Date: Sun, 9 Sep 2018 20:13:27 +0200
Subject: [PATCH] serial/rfc2217: only subnegotiate on value change
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This was suggested and is a direct copy of Uwe Kleine König's patch
from [1].

[1]: https://github.com/pyserial/pyserial/issues/376#issuecomment-418885211
Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
---
 serial/rfc2217.py | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/serial/rfc2217.py b/serial/rfc2217.py
index d962c1e8..2148512d 100644
--- a/serial/rfc2217.py
+++ b/serial/rfc2217.py
@@ -330,11 +330,15 @@ def set(self, value):
         the client needs to know if the change is performed he has to check the
         state of this object.
         """
-        self.value = value
-        self.state = REQUESTED
-        self.connection.rfc2217_send_subnegotiation(self.option, self.value)
-        if self.connection.logger:
-            self.connection.logger.debug("SB Requesting {} -> {!r}".format(self.name, self.value))
+        if value != self.value:
+            self.value = value
+            self.state = REQUESTED
+            self.connection.rfc2217_send_subnegotiation(self.option, self.value)
+            if self.connection.logger:
+                self.connection.logger.debug("SB Requesting {} -> {!r}".format(self.name, self.value))
+        else:
+            if self.connection.logger:
+                self.connection.logger.debug("SB Requesting {} -> {!r} (skipped)".format(self.name, self.value))

     def is_ready(self):
         """\