From 8708b1e16d13e0fec63b9b9361ef584465db8995 Mon Sep 17 00:00:00 2001
From: matejcik <ja@matejcik.cz>
Date: Tue, 17 Jul 2018 16:45:09 +0200
Subject: [PATCH 1/2] trezor: use TREZOR_PATH environment variable to specify
 device path

---
 libagent/device/trezor.py      |  8 ++++----
 libagent/device/trezor_defs.py | 22 ++++++++++++++++++----
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/libagent/device/trezor.py b/libagent/device/trezor.py
index 9b1f7e2..62f0bcd 100644
--- a/libagent/device/trezor.py
+++ b/libagent/device/trezor.py
@@ -106,13 +106,13 @@ class Trezor(interface.Device):
 
     def connect(self):
         """Enumerate and connect to the first available interface."""
-        transports = self._defs.enumerate_transports()
-        if not transports:
+        transport = self._defs.find_device()
+        if not transport:
             raise interface.NotFoundError('{} not connected'.format(self))
 
-        log.debug('transports: %s', transports)
+        log.debug('using transport: %s', transport)
         for _ in range(5):  # Retry a few times in case of PIN failures
-            connection = self._defs.Client(transport=transports[0],
+            connection = self._defs.Client(transport=transport,
                                            state=self.__class__.cached_state)
             self._override_pin_handler(connection)
             self._override_passphrase_handler(connection)
diff --git a/libagent/device/trezor_defs.py b/libagent/device/trezor_defs.py
index 49662d3..cf798e4 100644
--- a/libagent/device/trezor_defs.py
+++ b/libagent/device/trezor_defs.py
@@ -1,13 +1,27 @@
 """TREZOR-related definitions."""
 
 # pylint: disable=unused-import,import-error
+import os
+import logging
 
 from trezorlib.client import CallException, PinException
 from trezorlib.client import TrezorClient as Client
 from trezorlib.messages import IdentityType, PassphraseAck, PinMatrixAck, PassphraseStateAck
-from trezorlib.device import TrezorDevice
 
+try:
+    from trezorlib.transport import get_transport
+except ImportError:
+    from trezorlib.device import TrezorDevice
+    get_transport = TrezorDevice.find_by_path
 
-def enumerate_transports():
-    """Returns all available transports."""
-    return TrezorDevice.enumerate()
+log = logging.getLogger(__name__)
+
+
+def find_device():
+    """Selects a transport based on `TREZOR_PATH` env variable.
+    If unset, picks first connected device.
+    """
+    try:
+        return get_transport(os.environ.get("TREZOR_PATH"))
+    except Exception as e:
+        log.debug("Failed to find a Trezor device: %s", e)

From 8b85090fbaebd0a1edea97bdfa747a632ee93f19 Mon Sep 17 00:00:00 2001
From: matejcik <ja@matejcik.cz>
Date: Tue, 17 Jul 2018 16:50:53 +0200
Subject: [PATCH 2/2] trezor: usage for TREZOR_PATH variable

This is not a great place, as the variable will work anywhere,
but I couldn't find a better place to put it.

Also fixes a typo in the service definition.
---
 doc/README-SSH.md | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/README-SSH.md b/doc/README-SSH.md
index 343caa0..6d85faa 100644
--- a/doc/README-SSH.md
+++ b/doc/README-SSH.md
@@ -123,7 +123,7 @@ Description=trezor-agent SSH agent
 Requires=trezor-ssh-agent.socket
 
 [Service]
-Type=Simple
+Type=simple
 Environment="DISPLAY=:0"
 Environment="PATH=/bin:/usr/bin:/usr/local/bin:%h/.local/bin"
 ExecStart=/usr/bin/trezor-agent --foreground --sock-path %t/trezor-agent/S.ssh IDENTITY
@@ -133,6 +133,14 @@ If you've installed `trezor-agent` locally you may have to change the path in `E
 
 Replace `IDENTITY` with the identity you used when exporting the public key.
 
+If you have multiple Trezors connected, you can select which one to use via a `TREZOR_PATH`
+environment variable. Use `trezorctl list` to find the correct path. Then add it
+to the agent with the following line:
+````
+Environment="TREZOR_PATH=<your path here>"
+````
+Note that USB paths depend on the _USB port_ which you use.
+
 ###### `trezor-ssh-agent.socket`
 
 ````