commit af9be8c510a17a9ad4248d345307c72c94368873
author Jes B. Klinke <jbk@chromium.org> Sun Feb 20 17:32:00 2022 -0800
committer Timothy Trippel <5633066+timothytrippel@users.noreply.github.com> Wed Feb 23 10:21:04 2022 -0800
tree f33979810b85bd13a8bcf37bb540a840a2a09a26
parent 78972f7a4fc2ad28adf5445a6e2e965bf57c433e

[opentitantool] Gracefully handle requests for unsupported interfaces

As we plan to introduce a session proxy process, it is not desirable
that the persistent session process could panic!() if a single command
line invocation asks for e.g. I2C, though the particular USB backend
does not support I2C at all.

We already have a TransportError value to be used if asking for e.g. a
UART instance which does not exist: InvalidInstance.  It would be sent
via the TCP protocol and presented by the command line invocation.

This change introduces a new InvalidInterface.  And modifies the
default implementation in the Transport trait to return that instead
of panicking, in case the transport does not support UART, I2C or
whatever kind of interface it is being asked about.

Signed-off-by: Jes B. Klinke <jbk@chromium.org>
Change-Id: I7c0ff6e66a87ccd444be603be0075663d99cc280

sw/host/opentitanlib/src/transport/errors.rs

diff --git a/sw/host/opentitanlib/src/transport/errors.rs b/sw/host/opentitanlib/src/transport/errors.rs
index 327389d..0e6a7c2 100644
--- a/sw/host/opentitanlib/src/transport/errors.rs
+++ b/sw/host/opentitanlib/src/transport/errors.rs
@@ -20,6 +20,8 @@
     UsbGenericError(String),
     #[error("Error opening USB device: {0}")]
     UsbOpenError(String),
+    #[error("Transport does not support {0:?}")]
+    InvalidInterface(TransportInterfaceType),
     #[error("Transport does not support {0:?} instance {1}")]
     InvalidInstance(TransportInterfaceType, String),
     #[error("Encountered non-unicode device path")]

sw/host/opentitanlib/src/transport/mod.rs

diff --git a/sw/host/opentitanlib/src/transport/mod.rs b/sw/host/opentitanlib/src/transport/mod.rs
index 2afd2ec..3f0f6f1 100644
--- a/sw/host/opentitanlib/src/transport/mod.rs
+++ b/sw/host/opentitanlib/src/transport/mod.rs
@@ -79,23 +79,23 @@
 
     /// Returns a SPI [`Target`] implementation.
     fn spi(&self, _instance: &str) -> Result<Rc<dyn Target>> {
-        unimplemented!();
+        Err(TransportError::InvalidInterface(TransportInterfaceType::Spi))
     }
     /// Returns a I2C [`Bus`] implementation.
     fn i2c(&self, _instance: &str) -> Result<Rc<dyn Bus>> {
-        unimplemented!();
+        Err(TransportError::InvalidInterface(TransportInterfaceType::I2c))
     }
     /// Returns a [`Uart`] implementation.
     fn uart(&self, _instance: &str) -> Result<Rc<dyn Uart>> {
-        unimplemented!();
+        Err(TransportError::InvalidInterface(TransportInterfaceType::Uart))
     }
     /// Returns a [`GpioPin`] implementation.
     fn gpio_pin(&self, _instance: &str) -> Result<Rc<dyn GpioPin>> {
-        unimplemented!();
+        Err(TransportError::InvalidInterface(TransportInterfaceType::Gpio))
     }
     /// Invoke non-standard functionality of some Transport implementations.
     fn dispatch(&self, _action: &dyn Any) -> Result<Option<Box<dyn Serialize>>> {
-        Err(TransportError::UnsupportedOperation.into())
+        Err(TransportError::UnsupportedOperation)
     }
 }